In vivo noninvasive evaluation of abnormal patellar tracking during squatting in patients with patellofemoral pain

Abnormal patellar sagittal spatial kinematics in patients with patellofemoral pain: an in vivo dynamic CT study

BACKGROUND

Patellofemoral joint kinematics is a complex three-dimensional(3D) motion, involving shift and rotation in the coronal, sagittal, and axial directions. Quantifying patellar tracking only at the axial level of the patella or with two-dimensional(2D) parameters may not be comprehensive. The current study sought to explore the spatial kinematics characteristics of the patella in three directions, especially the sagittal plane in patients with patellofemoral pain (PFP) based on Four-dimensional computed tomography (4D-CT).

METHODS

A total of 35 knees with PFP and 35 controls from March 2023 to May 2024 were evaluated. 3D shift and tilt of the patella were measured in the patellofemoral joint coordinate system established by MIMICS. The 3D shift and tilt of the patella in three directions (coronal, sagittal, and axial) were evaluated. Differences between groups were analyzed using two-way repeated measures ANOVA.

RESULTS

The 3D tiltsagittal and 3D tiltaxial trends differed between the two groups (P = 0.020, 0.018, respectively). The 3D shiftsagittal at knee flexions of 50° to 70° was significantly increased in the PFP group compared to the control group (P = 0.009, 0.015, respectively). The 3D tiltsagittal was significantly greater in the PFP group than in the control group at -10° to 10° and 50° to 70° of knee flexion (P = 0.004, 0.005, 0.046, 0.007, respectively). The 3D tiltaxial was significantly greater in the PFP group than in the control group at -10° to 0° and 40° to 70° of knee flexion (P = 0.033, 0.011, 0.004, 0.015, respectively). The 3D shiftcoronal at knee flexions of -10° to 20° were significantly decreased in the PFP group compared to the control group (P = 0.002, < 0.001, 0.018, respectively).

CONCLUSION

It is necessary to evaluate the spatial position characteristics of the patellofemoral joint and the stability of the patella from multiple planes and angles at the dynamic level. Analyzing the spatial multi-plane kinematic characteristics of the patellofemoral joint may help in determining the etiology of PFP.

Abnormal sagittal patellar tilt during active knee flexion and extension on 4DCT might be associated with patellofemoral pain

BACKGROUND

The quadriceps during activities mainly affect patellar movement in the sagittal plane. This study was to analyze the pattern of sagittal patellar tilt in patellofemoral pain (PFP) patients by four-dimensional computed tomography (4DCT).

METHODS

Thirty-four knees of PFP patients and 34 control knees were scanned with 4DCT. Patella-patellar tendon angle (P-PTA), patella-lateral tibial plateau angle (P-LTPA), patella-screen horizontal line angle (P-SHLA), articular facet of the patella-lateral tibial plateau angle (PA-LTPA), articular facet of the patella-screen horizontal line angle (PA-SHLA), and upper margin of the patella-quadriceps tendon angle (PU-QTA) were used to evaluate the sagittal patellar tilt. Two-factor repeated-measures ANOVA was used to compare all parameters between the two groups.

RESULTS

At 30°-40° of flexion, P-PTA was significantly lower in PFP group than in control group (p = 0.004). At 0°-10°, PU-QTA was significantly higher in PFP group than in control group (p = 0.027). During flexion and extension, P-SHLA and PA-SHLA were significantly higher in PFP group than in control group, but there were no significant differences in P-LTPA and PA-LTPA. From - 10° to 30°, P-PTA decreased as the knee flexion angle increased. PU-QTA, P-LTPA, and PA-LTPA also decreased as the knee flexion angle increased, but P-SHLA and PA-SHLA increased.

CONCLUSIONS

In PFP group, sagittal patellar tilt was abnormal, and patella showed anterior tilt relative to the screen horizontal line during active knee flexion and extension. The pattern of patellar sagittal motion during dynamic process was consistent between PFP and control groups. The characteristics of patellofemoral sagittal alignment should not be ignored when analyzing patellofemoral stability.

Digging into the Cause of Abnormal Patellar Kinematics After Open-Wedge High Tibial Osteotomy via a Quantitative Study on In Vivo Soft Tissue Functional Changes

The biomechanical mechanism of postoperative patellofemoral joint (PFJ) complications after open-wedge high tibial osteotomy (OWHTO) has not been investigated. This study was to determine the length changes in the patellar tendon (PT), medial patellotibial ligament (MPTL), medial patellofemoral ligament (MPFL), and quadriceps moment arm (QMA) during staircase motion before and after OWHTO. Computed tomography (CT) scans of 15 patients' lower extremities were used to reconstruct three-dimensional models, and magnetic resonance imaging (MRI) of the knee and hip joints was used to mark the soft tissue footprints. Then, such soft tissue lengths were quantified by a dual fluoroscopic imaging system (DFIS). Additionally, function scores were used to assess patient outcome changes. The results showed that there was a contraction of the PT after OWHTO due to its adhesion to the osteotomy site, causing PT length to be negatively correlated to the open-wedge angle. In addition, the shortening of the MPTL and QMA caused patellar instability and an imbalance in the strength of the lower extremities. Additionally, most knee function scores improved after OWHTO, except the Feller scores. Multiple methods should be considered to optimize surgical procedures, postoperative rehabilitation, and physical therapy.

Effects of differences in femoral anteversion and hip flexion angle on hip abductor muscles activity during clam exercise in females

This study aimed to determine differences in the hip abductor muscle activity during clam exercise at different hip flexion and femoral anteversion angles. Thirty healthy females were divided into two groups based on the femoral anteversion angle: the excessive femoral anteversion group and the normal group. Clam exercise was performed at three different hip flexion angles (60°, 45°, and 30°). Tensor fascia latae, gluteus medius, and superior portion of gluteus maximus activities were measured during the exercise, and the results were normalized to the activity during maximum voluntary isometric contraction to calculate the gluteal-to-tensor fascia latae muscle activation index. The superior portion of gluteus maximus activities at a hip flexion of 60° and 45° were greater than that at 30°. The excessive femoral anteversion group had a lower gluteal-to-tensor fascia latae muscle activation index than the normal group; the gluteal-to-tensor fascia latae muscle activation index for hip flexion at 60° was higher than that at 45°, and the gluteal-to-tensor fascia latae muscle activation index for hip flexion at 60° and 45° were higher than that at 30°. Therefore, the femoral anteversion angle and hip joint position were related to the activity of the hip abductor muscles during clam exercise. These findings may provide a rationale for instructing exercises to maximize the activity of the hip abductor muscles in individuals with an excessive femoral anteversion angle.

Automated personalization of biomechanical knee model

PURPOSE

Patient-specific biomechanical models of the knee joint can effectively aid in understanding the reasons for pathologies and improve diagnostic methods and treatment procedures. For deeper research of knee diseases, the development of biomechanical models with appropriate configurations is essential. In this study, we mainly focus on the development of a personalized biomechanical model for the investigation of knee joint pathologies related to patellar motion using automated methods.

METHODS

This study presents a biomechanical model created for patellar motion pathologies research and some techniques for automating the generation of the biomechanical model. To generate geometric models of bones, the U-Net neural network was adapted for 3D input datasets. The method uses the same neural network for segmentation of femur, tibia, patella and fibula. The total size of the train/validation (75/25%) dataset is 18,183 3D volumes of size 512 × 512 × 4 voxels. The configuration of the biomechanical knee model proposed in the paper includes six degrees of freedom for the tibiofemoral and patellofemoral joints, lateral and medial contact surfaces for femur and tibia, and ligaments, representing, among other things, the medial and lateral stabilizers of the knee cap. The development of the personalized biomechanical model was carried out using the OpenSim software system. The automated model generation was implemented using OpenSim Python scripting commands.

RESULTS

The neural network for bones segmentation achieves mean DICE 0.9838. A biomechanical model for realistic simulation of patellar movement within the trochlear groove was proposed. Generation of personalized biomechanical models was automated.

CONCLUSIONS

In this paper, we have implemented a neural network for the segmentation of 3D CT scans of the knee joint to produce a biomechanical model for the study of knee cap motion pathologies. Most stages of the generation process have been automated and can be used to generate patient-specific models.

Meta-analysis of factors influencing anterior knee pain after total knee arthroplasty

BACKGROUND

Total knee arthroplasty (TKA) is a mature procedure recommended for correcting knee osteoarthritis deformity, relieving pain, and restoring normal biomechanics. Although TKA is a successful and cost-effective procedure, patient dissatisfaction is as high as 50%. Knee pain after TKA is a significant cause of patient dissatisfaction; the most common location for residual pain is the anterior region. Between 4% and 40% of patients have anterior knee pain (AKP).

AIM

To investigate the effect of various TKA procedures on postoperative AKP.

METHODS

We searched PubMed, EMBASE, and Cochrane from January 2000 to September 2022. Randomized controlled trials with one intervention in the experimental group and no corresponding intervention (or other interventions) in the control group were collected. Two researchers independently read the title and abstract of the studies, preliminarily screened the articles, and read the full text in detail according to the selection criteria. Conflicts were resolved by consultation with a third researcher. And relevant data from the included studies were extracted and analyzed using Review Manager 5.4 software.

RESULTS

There were 25 randomized controlled trials; 13 were comparative studies with or without patellar resurfacing. The meta-analysis showed no significant difference between the experimental and control groups (P = 0.61). Six studies were comparative studies of circumpatellar denervation vs non-denervation, divided into three subgroups for meta-analysis. The two-subgroup meta-analysis showed no significant difference between the experimental and the control groups (P = 0.31, P = 0.50). One subgroup meta-analysis showed a significant difference between the experimental and control groups (P = 0.001). Two studies compared fixed-bearing TKA and mobile-bearing TKA; the results meta-analysis showed no significant difference between the experimental and control groups (P = 0.630). Two studies compared lateral retinacular release vs non-release; the meta-analysis showed a significant difference between the experimental and control groups (P = 0.002); two other studies compared other factors.

CONCLUSION

Patellar resurfacing, mobile-bearing TKA, and fixed-bearing TKA do not reduce the incidence of AKP. Lateral retinacular release can reduce AKP; however, whether circumpatellar denervation can reduce AKP is controversial.

Home-based exercise program and Health education in patients with patellofemoral pain: a randomized controlled trial

BACKGROUND

Patellofemoral pain (PFP) is one of the most common disorders of the knee joint. Home-based exercise is an effective intervention to achieve self-management for chronic diseases. This study evaluated the effects of home-based exercise and health education in patients with PFP.

METHODS

Patients who had PFP were randomly allocated to an intervention group (IG) or control group (CG). Patients in the IG received a 6-week tailored home-based exercise program with health education via remote support, while patients in the CG group only received health education. Clinical outcomes were compared using the Anterior Knee Pain Scale (AKPS) to measure function and the Visual Analog Scale (VAS) to measure "worst pain" and "pain with daily activity". Muscle strength was measured according to the peak torque of the knee muscles using an isokinetic system.

RESULTS

Among a total of 112 participants screened for eligibility, 38 were randomized and analyzed, including 19 participants in the intervention group and 19 participants in the control group. There were no significant differences in baseline characteristics between the groups. At 6-week follow-up, the intervention group showed a greater worst pain reduction (between-group difference, -19.3 [95%CI, -23.2 to -15.5]; P < 0.01) and pain with daily activity (between-group difference, -22.9 [95%CI, -28.3 to -17.4]; P < 0.01) than the control group. Similarly, the intervention group had better improvements in AKPS (between-group difference, 9.0 [95%CI, 4.1 to 13.9]; P < 0.01) and knee extensor strength (between-group difference, 20.1 [95%CI, 14.5 to 25.8]; P < 0.01), compared to the control group. No adverse events were reported.

CONCLUSION

Home-based exercise and health education resulted in less pain, better function, and higher knee muscle strength compared with no exercise in patients with PFP. A large randomized controlled trial with long-term follow-up is required to confirm these findings.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR2200056224 ( https://www.chictr.org.cn/showproj.aspx?proj=135506 ). Registered on February 1, 2022.

Patellofemoral pain syndrome assessed by Lysholm score, radiological and biorheometric measurements

INTRODUCTION

The aim of In this study was to verify the relationship among clinical indicators of patellofemoral pain syndrome (PFPS) and the results of modifying radiological investigation. Previous research suggests that there is a poor association between them. Therefore we have employed a technique for the functional evaluation of PFPS based on measuring the stiffness of the knee joint during passive flexion (biorheometry).

METHOD

The correlation between clinical examination and a standardized Lysholm score, radiological and biorheometric measures was investigated in the 28 knee joints of 14 subjects exhibiting clinical features of PFPS. A modified axial radiological projection of the patellofemoral articulation in 90° of flexion provided the parameters quantifying the anatomical - morphological arrangement of the patellofemoral joint. The biorheometric properties of the knee were evaluated using a custom made measuring apparatus during passive flexion and extension of the knee.

RESULTS

Our results confirm that the link between the clinical findings and the X-ray imaging examinations was not evident. On the contrary, the biorheometric examination proved to correlate well with the clinical symptoms of PFPS. Parameters were identified which can characterize the biorheograms of people suffering PFPS.

CONCLUSIONS

Analysis of the relationship among the clinical, radiological and biorheometric examinations leads to the recommendation that biorheometric examination is an effective method for the objective assessment of PFPS.

Contact area and pressure changes of patellofemoral joint during stair ascent and stair descent

PURPOSE

To investigate the differences of patellofemoral joint pressure and contact area between the process of stair ascent and stair descent.

METHODS

The finite element models of 9 volunteers without disorders of knee (9 males) to estimate patellar cartilage pressure during the stair ascent and the stair descent. Simulations took into account cartilage morphology from magnetic resonance imaging, joint posture from weight-bearing magnetic resonance imaging, and ligament model. The three-dimension models of the patella, femur and tibia were developed with the medical image processing software, Mimics 11.1. The ligament was established by truss element of the non-linear FE solver. The equivalent gravity direction (-z direction) load was applied to the whole end of femur (femoral head) according to the body weight of the volunteers, and the force of patella was observed. A paired-samples t-test or Wilcoxon rank sum test to make comparisons between stair ascent and stair descent. Statistical analyses were performed using SPSS 22.0 using a P value of 0.05 to indicate significance.

RESULTS

During the stair descent (knee flexion at 30°), the contact pressure of the patella was 2.59 ± 0.06Mpa. The contact pressure of femoral trochlea cartilage was 2.57 ± 0.06Mpa. During the stair ascent (knee flexion at 60°), the contact pressure with patellar cartilage was 2.82 ± 0.08Mpa. The contact pressure of the femoral trochlea cartilage was 3.03 ± 0.11Mpa. The contact area between patellar cartilage and femoral trochlea cartilage was 249.27 ± 1.35mm2 during the stair descent, which was less than 434.32 ± 1.70mm2 during the stair ascent. The area of high pressure was located in the lateral area of patella during stair descent and the area of high pressure was scattered during stair ascent.

CONCLUSION

There are small change in the cartilage contact pressure between stair ascent and stair descent, indicating that the joint adjusts the contact pressure by increasing the contact area.

Using Dual-Orthogonal Fluoroscopy and CT to Assess the Relationship Between Knee Morphology and Patellar Kinematics in Patients With Patellofemoral Pain

INTRODUCTION

Patellofemoral pain (PFP) is one of the most common knee overuse injuries, with studies suggesting PFP as a precursor for early knee osteoarthritis. The etiology of PFP is multi-factorial; however, patellar mal-tracking has been regarded as a primary mechanism. Details of this multi-factorial mechanism have been unclear because of the limitations in evaluating in-vivo, three-dimensional (3D) patellofemoral joint movement during dynamic activities accurately. Alternatively, studies have demonstrated the high accuracy and repeatability of dual fluoroscopy and CT/MRI for measuring knee joint motion.

OBJECTIVE

This study uses dual fluoroscopy and CT to investigate the associations between joint morphology and patellar kinematics in healthy controls and subjects with PFP.

METHODS

Eight PFP females (29.7±10.6 years) and 10 healthy females (25.0±7.7 years) were recruited and screened by a sports medicine physician. CT imaging was performed on participants in a supine with the knee extended, and ankle and hip in neutral alignment. Dual-orthogonal fluoroscopy measured patellar movement while participants performed a lunge task. A calibration algorithm was used to register the 3D CT model to 2D fluoroscopy image to calculate the relative position and angles of the patella based on the clinical definition of patellar motion. Measures of patellar and trochlear morphology were generated and correlated to kinematic data.

RESULTS AND CONCLUSION

There was a significant difference in the patellar-to-trochlear width ratio; however, no other significant differences in CT morphology measurements were present between groups. For PFP patients in the weight-bearing extended position, there was a moderate positive correlation between the patellar-to-trochlear width ratio and medial-lateral patellar shift (τ = 0.643, p = 0.026). Healthy controls in this position demonstrated a moderate positive correlation between the lateral-trochlear inclination angle and medial-lateral patellar shift (τ = 0.600, p = 0.016) and moderate negative correlation between medial trochlear inclination angle and medial-lateral patellar shift (τ = -0.511, p = 0.040). The findings suggest that, for this cohort, there is correlation between morphology and patellar kinematics. Passive and active stabilizers likely have a role in mal-tracking.

Clinical Significance of the Static and Dynamic Q-angle

Q-angle represents the resultant force vector of the quadriceps and patellar tendons acting on the patella. An increased Q-angle has been considered a risk factor for many disorders and injuries. This literature review challenges the clinical value of static Q-angle and recommends a more dynamic movement evaluation for making clinical decisions. Although there are many articles about static Q-angle, few have assessed the value of dynamic Q-angle. We searched Scopus and PubMed (until September 2021) to identify and summarize English-language articles evaluating static and dynamic Q-angle, including articles for dynamic knee valgus (DKV) and frontal plane projection angle. We also used textbooks and articles from references to related articles. Although static Q-angle measurement is used systematically in clinical practice for critical clinical decisions, its interpretation and clinical translation present fundamental and intractable limitations. To date, it is acceptable that mechanisms that cause patellofemoral pain and athletic injuries have a stronger correlation with dynamic loading conditions. Dynamic Q-angle has the following three dynamic elements: frontal plane (hip adduction, knee abduction), transverse plane (hip internal rotation and tibia external rotation), and patella behavior. Measuring one out of three elements (frontal plane) illustrates only one-third of this concept. Static Q-angle lacks biomechanical meaning and utility for dynamic activities. Although DKV is accompanied by hip and tibia rotation, it remains a frontal plane measurement, which provides no information about the transverse plane and patella movement. However, given the acceptable reliability and the better differentiation capability, DKV assessment is recommended in clinical practice.

Adolescents and adults with patellofemoral pain exhibit distinct patellar maltracking patterns

BACKGROUND

Chronic idiopathic patellofemoral pain is associated with patellar maltracking in both adolescents and adults. To accurately target the underlying, patient-specific etiology, it is crucial we understand if age-of-pain-onset influences maltracking.

METHODS

Twenty adolescents (13.9 ± 1.4 years) and 20 adults (28.1 ± 4.9 years) female patients with idiopathic patellofemoral pain (age-of-pain-onset: < 14 and > 18 years of age, respectively) formed the patient cohort. Twenty adolescents and 20 adults (matched for gender, age, and body mass index) formed the control cohort. We captured three-dimensional patellofemoral kinematics during knee flexion-extension using dynamic MRI. Patellar maltracking (deviation in patient-specific patellofemoral kinematics, relative to their respective age-controlled mean values) was the primary outcome measure, which was compared between individuals with adolescent-onset and adult-onset patellofemoral pain using ANOVA and discriminant analysis.

FINDINGS

The female adolescent-onset patellofemoral pain cohort demonstrated increased lateral (P = 0.032), superior (P = 0.007), and posterior (P < 0.001) maltracking, with increased patellar flexion (P < 0.001) and medial spin (P = 0.002), relative to the adult-onset patellofemoral pain cohort. Post-hoc analyses revealed increased lateral shift [mean difference ± 95% confidence interval = -2.9 ± 2.1 mm at 10° knee angle], posterior shift [-2.8 ± 2.1 mm, -3.3 ± 2.3 mm & -3.1 ± 2.4 mm at 10°, 20°& 30°], with greater patellar flexion [3.8 ± 2.6 mm & 5.0 ± 2.8 mm, at 20°& 30°] and medial spin [-2.2 ± 1.7 mm & -3.4 ± 2.3 mm at 20°& 30°]. Axial-plane maltracking accurately differentiated the patient age-of-pain-onset (60-75%, P < 0.001).

INTERPRETATION

Age-of-pain-onset influences the maltracking patterns seen in patients with patellofemoral pain; with all, but 1, degree of freedom being unique in the adolescent-onset-patellofemoral pain cohort. Clinical awareness of this distinction is crucial for correctly diagnosing a patient's pain etiology and optimizing interventional strategies.

A Word of Caution for Future Studies in Patellofemoral Pain: A Systematic Review With Meta-analysis

BACKGROUND

Patellar maltracking is widely accepted as an underlying mechanism of patellofemoral pain. However, methodological differences in the literature hinder our ability to generate a universal quantitative definition of pathological patellofemoral kinematics (patellar maltracking) in patellofemoral pain, leaving us unable to determine the cause of patellofemoral pain.

PURPOSE

To systematically review the literature to provide evidence regarding the influence of confounding variables on patellofemoral kinematics.

STUDY DESIGN

Systematic review and random effects meta-analysis of control-case studies.

METHODS

A literature search of case-control studies that evaluated patellofemoral kinematics at or near full extension and were written in English was conducted using Embase, PubMed, Scopus, and Web of Science up to September 2019. Cases were defined as patients with patellofemoral pain. Studies were eliminated if they lacked quantitative findings; had a primary aim to assess therapy efficacy; or included participants with osteoarthritis and/or previous trauma, pathology, or surgery. A quality assessment checklist was employed to evaluate each study. Meta-analyses were conducted to determine the influence of confounding variables on measures of patellofemoral kinematics.

RESULTS

Forty studies met the selection criteria, with quality scores ranging from 13% to 81%. Patient characteristics, data acquisition, and measurement methods were the primary sources of methodological variability. Active quadriceps significantly increased lateral shift (standardized mean difference [SMD]_shift = 0.33; P = .0102) and lateral tilt (SMD_tilt = 0.43; P = .006) maltracking. Individuals with pain secondary to dislocation had greater effect sizes for lateral maltracking than had those with isolated patellofemoral pain (ΔSMD_shift = 0.71, P = .0071; ΔSMD_tilt = 1.38, P = .0055).

CONCLUSION

This review exposed large methodological variability across the literature, which not only hinders the generalization of results, but ultimately mitigates our understanding of the underlying mechanism of patellofemoral pain. Although our meta-analyses support the diagnostic value of maltracking in patellofemoral pain, the numerous distinct methods for measuring maltracking and the limited control for cofounding variables across the literature prohibit defining a single quantitative profile. Compliance with specific standards for anatomic and outcome measures must be addressed by the scientific and clinical community to establish methodological uniformity in this field.

Development of an innovative measurement method for patellar tracking disorder

In this study, we investigated whether the measurement of patellar tracking can be used as a diagnostic parameter of patellofemoral joint disease. Patellar tracking is defined as the movement of the patella in relation to the femorotibial joint within the full range of flexion and extension of the knee joint. The PubMed, EMBASE, Medline, PsychINFO, and AMED databases were used to find relevant articles. Analyzed were the patellar tracking coordinate system and the measurement objects, precision, methods used in those studies, as well as the results obtained. Origin points for coordinate systems varied across the studies. The research object and methods of patellar tracking varied in the studies. Most studies focused on a static description of the internal and external displacement and the internal and external inclination. The in vivo, noninvasive, and six degrees of freedom evaluation of patellar tracking reflect patellar motion more comprehensively, though each of these methods does so in different ways. Dynamic and quantitative evaluation of patellar tracking is still lacking in clinical work. Accurate and quantitative patellar tracking measurement could provide clinicians with a comprehensive evaluation of the stability of the knee joint.

Effect of Vastus Medialis Loss on Rabbit Patellofemoral Joint Contact Pressure Distribution

Vastus medialis (VM) weakness is thought to alter patellar tracking, thereby changing the loading of the patellofemoral joint (PFJ), resulting in patellofemoral pain. However, it is challenging to measure VM force and weakness in human studies, nor is it possible to measure the associated mechanical changes in the PFJ. To obtain fundamental insight into VM weakness and its effects on PFJ mechanics, the authors determined PFJ loading in the presence of experimentally simulated VM weakness. Skeletally mature New Zealand White rabbits were used (n = 6), and the vastus lateralis, VM, and rectus femoris were stimulated individually through 3 custom-built nerve cuff electrodes. Muscle torque and PFJ pressure distribution were measured while activating all muscles simultaneously, or when the vastus lateralis and rectus femoris were activated, while VM was not, to simulate a quadriceps muscle strength imbalance. For a given muscular joint torque, peak pressures were greater and joint contact areas were smaller when simulating VM weakness compared with the condition where all muscles were activated simultaneously. The results in the rabbit model support that VM weakness results in altered PFJ loading, which may cause patellofemoral pain, often associated with a strength imbalance of the knee extensor muscle group.

The effect of patellofemoral pain syndrome on patellofemoral joint kinematics under upright weight-bearing conditions

Patellofemoral pain (PFP) is commonly caused by abnormal pressure on the knee due to excessive load while standing, squatting, or going up or down stairs. To better understand the pathophysiology of PFP, we conducted a noninvasive patellar tracking study using a C-arm computed tomography (CT) scanner to assess the non-weight-bearing condition at 0° knee flexion (NWB0°) in supine, weight-bearing at 0° (WB0°) when upright, and at 30° (WB30°) in a squat. Three-dimensional (3D) CT images were obtained from patients with PFP (12 women, 6 men; mean age, 31 ± 9 years; mean weight, 68 ± 9 kg) and control subjects (8 women, 10 men; mean age, 39 ± 15 years; mean weight, 71 ± 13 kg). Six 3D-landmarks on the patella and femur were used to establish a joint coordinate system (JCS) and kinematic degrees of freedom (DoF) values on the JCS were obtained: patellar tilt (PT, °), patellar flexion (PF, °), patellar rotation (PR, °), patellar lateral-medial shift (PT_x, mm), patellar proximal-distal shift (PT_y, mm), and patellar anterior-posterior shift (PT_z, mm). Tests for statistical significance (p < 0.05) showed that the PF during WB30°, the PT_y during NWB0°, and the PT_z during NWB0°, WB0°, and WB30° showed clear differences between the patients with PFP and healthy controls. In particular, the PF during WB30° (17.62°, extension) and the PT_z during WB0° (72.5‬0 mm, posterior) had the largest rotational and translational differences (JCS Δ = patients with PFP—controls), respectively. The JCS coordinates with statistically significant difference can serve as key biomarkers of patellar motion when evaluating a patient suspected of having PFP. The proposed method could reveal diagnostic biomarkers for accurately identifying PFP patients and be an effective addition to clinical diagnosis before surgery and to help plan rehabilitation strategies.

Patellofemoral Mechanics: a Review of Pathomechanics and Research Approaches

PURPOSE OF REVIEW

The patellofemoral joint is a complicated articulation of the patella and femur that is prone to pathologies. The purpose of this review is to report on the current methods of investigating patellofemoral mechanics, factors that affect joint function, and future directions in patellofemoral joint research with emerging technologies and techniques.

RECENT FINDINGS

While previous hypotheses have suggested that the patella is only a moment arm extender, recent literature has suggested that the patella influences the control of knee moments and forces acting on the tibia as well as contributes to various aspects of patellar function with minimal neural input. With advancements in simulating a six-degrees-of-freedom patellofemoral joint, we have gained a better understanding of patella motion and have shown that geometry and muscle activations impact patella mechanics. Research into influences on patella mechanics from other joints such as the hip and foot has become more prevalent. In this review, we report current in vivo, in vitro, and in silico approaches to studying the patellofemoral joint. Kinematic and anatomical factors that affect patellofemoral joint function such as patella alta and tilt or bone morphology and ligaments are discussed. Moving forward, we suggest that advanced in vivo dynamic imaging methods coupled to musculoskeletal simulation will provide further understanding of patellofemoral pathomechanics and allow engineers and clinicians to design interventions to mitigate or prevent patellofemoral pathologies.

Accuracy and Reliability of the Visual Assessment of Patellar Tracking

BACKGROUND

Abnormal patellar tracking is described as a "J-sign" when the patella exhibits excessive lateral displacement during active knee extension.

PURPOSE

To determine (1) the accuracy and reliability of the visual assessment of patellar tracking when viewed by surgeons with patellofemoral expertise and (2) whether surgeon experience (in years) correlates with the ability to accurately identify the presence and severity of patellar maltracking.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 2.

METHODS

Using a web-based assessment, 32 orthopaedic surgeon members of the International Patellofemoral Study Group determined the presence or absence of maltracking (≥2 quadrants of lateral translation) in 10 single-knee videos of patients with patellar instability during active knee extension (qualitative analysis). Surgeons then graded patellar tracking in 20 single-knee videos as follows: 0 (<1 patellar quadrant of lateral translation), 1 (1 to <2 quadrants), 2 (2 to <3 quadrants), or 3 (≥3 quadrants) (quantitative analysis). Responses were compared with a previously described grading system using patellar bisect offset measured with 4-dimensional computed tomography. We evaluated the association between number of years of surgeon experience and the ability to correctly identify and grade patellar tracking. A total of 22 surgeons repeated the survey 3 months later, and their answers were matched to the first survey, allowing for assessment of intraobserver reliability.

RESULTS

In the qualitative analysis, surgeons correctly identified videos as showing patellar maltracking 68% of the time (κ = 0.45). In the quantitative analysis, 53%, 51%, 48%, and 68% of surgeons correctly identified maltracking of grades 3, 2, 1, and 0, respectively (κ = 0.42). Surgeon experience did not correlate with ability to identify the presence (P = .59) or grade (P = .35) of patellar maltracking. Respondent answers from the second survey demonstrated inadequate intraobserver reliability (κ = 0.48).

CONCLUSION

Using visual assessment alone, surgeons correctly identified patellar maltracking in approximately two-thirds of videos and correctly graded patellar maltracking in half. Inter- and intraobserver reliability were inadequate to support the use of visual assessment alone for detecting the presence or grade of patellar maltracking. Surgeon experience did not correlate with ability to identify the presence or grade of patellar maltracking.

Unilateral anterior knee pain is associated with increased patellar lateral position after stressed lateral translation

PURPOSE

To objectively compare side-to-side patellar position and mobility in patients with idiopathic unilateral anterior knee pain (AKP) using a stress-testing device concomitantly with magnetic resonance imaging. It is hypothesized that the painful knees present greater patellar mobility than the contralateral non-painful knees.

METHODS

From a total sample of 359 patients, 23 patients with idiopathic unilateral AKP (30.9 years, 23.4 kg/m², 43% males) were included within the present study. Both knees of all the patients were examined by conventional imaging, including the measurement of trochlear sulcus angle, Caton-Deschamps index, tibial tuberosity to trochlear groove distance, patellar tilt angle and patellar subluxation (both at rest and upon quadriceps contraction). Additionally, the same patients underwent stress testing (Porto Patella Testing Device); these measurements were taken with the patella at rest, after lateral patellar translation and after lateral patellar tilt. Clinical and functional outcomes were obtained using physical examination and the Kujala and Lysholm scores.

RESULTS

Painful knees showed statistically significant higher patellar lateral position after stressed lateral translation than non-painful knees (p = 0.028), 9.8 ± 3.6 mm and 7.1 ± 6.3 mm, respectively. The adjusted multivariate logistic model identified the patellar position after lateral displacement to be significantly associated with AKP (OR = 1.165) and the model (AUC = 0.807, p < 0.001) showed reasonable sensitivity (67%) and specificity (73%).

CONCLUSION

Patients with idiopathic unilateral AKP with morphologically equivalent knees showed statistically significant increased patellar lateral position after stressed lateral displacement in their painful knee. The greater lateral patellar mobility quantified by the PPTD testing brings more objectivity to the diagnosis.

LEVEL OF EVIDENCE

II.

Dynamic Evaluation of Patellofemoral Instability: A Clinical Reality or Just a Research Field? A Literature review

Patellofemoral instability (PFI) is one of the most disabling conditions in the knee, often affecting young individuals. Despite its not uncommon presentation, the underlying biomechanical features leading to this entity are not entirely understood. The suitability of classic physical examination manoeuvres and imaging tests is a matter of discussion among treating surgeons, and so are the findings provided by these means. A potential cause for this lack of consensus is the fact that, classically, the diagnostic approach for PFI has relied on statically obtained data. Many authors advocate for the study of this entity in a dynamic scenario, closer to the actual situation in which the instability episodes occur. In this literature review, we have compiled the available data from the last decades regarding dynamic evaluation methods for PFI and related conditions. Several categories are presented, grouping the related techniques and devices: physical examination, imaging modalities (ultrasound (US), magnetic resonance imaging (MRI), computed tomography (CT) and combined methods), arthroscopic evaluation, and others. In conclusion, although a vast number of quality studies are presented, in which comprehensive data about the biomechanics of the patellofemoral joint (PFJ) are described, this evidence has not yet reached clinical practice universally. Most of the data still stays in the research field and is seldom employed to assist a better understanding of the PFI cases and their ideal treatment targets.

Medial and Lateral Patellofemoral Joint Retinaculum Thickness in People With Patellofemoral Pain: A Case-Control Study

OBJECTIVES

To measure the medial and lateral retinaculum thickness in individuals with and without patellofemoral pain using ultrasound and to assess associations with the symptom duration and function.

METHODS

Medial and lateral patellofemoral joint retinaculum thicknesses of 32 knees (16 with patellofemoral pain and 16 asymptomatic) were measured with B-mode ultrasound at 0.5, 1, and 1.5 cm from the patella border. Participants with patellofemoral pain completed a Kujala questionnaire, and both groups underwent a single-leg squat performance assessment. Two-way analyses of variance (site × group) determined the overall effect, and Cohen d values were calculated to describe the magnitude of the difference for each measurement.

RESULTS

The groups were matched for age, height, and weight. Compared to controls, participants with patellofemoral pain had thicker lateral (overall effect, P = .03) and medial (overall effect, P < 0.01) retinacula. No correlations between retinaculum thickness and Kujala scores (lateral retinaculum, r = 0.106 [0.5 cm], -0.093 [1 cm], and -0.207 [1.5 cm]; and medial retinaculum, r = 0.059, 0.109, and -0.219), symptom duration (lateral retinaculum, r = 0.001, -0.041, and 0.302; and medial retinaculum, r = -0.027, -0.358, and -0.346), or single-leg squat performance scores (lateral retinaculum, r = 0.051, 0.114, and 0.046; and medial retinaculum, r = -0.119, -0.292, and 0.011) were observed.

CONCLUSIONS

Increased lateral and medial retinaculum thickness in individuals with patellofemoral pain compared to controls identifies structural changes that may be associated with the pathogenesis of patellofemoral pain. The absence of a significant correlation between retinaculum thickness and the symptom duration or function further shows a lack of an association between structure and function in individuals with patellofemoral pain.

Research Methods and Progress of Patellofemoral Joint Kinematics: A Review

Patellofemoral pain syndrome has a high morbidity, and its pathology is closely associated with patellofemoral joint kinematics. A series of in vivo and in vitro studies have been conducted to explore patellofemoral kinematics, and the findings are relevant to the diagnosis, classification, and management of patellofemoral diseases and even the whole knee joint. However, no definite conclusion on normal patellofemoral kinematics has been established. In this study, the measurement methodologies of patellofemoral kinematics (including data collection methods, loading conditions, and coordinate system) as well as their advantages and limitations were reviewed. Motion characteristics of the patella were analyzed. During knee flexion, the patellar flexion angle lagged by 30–40% compared to the tibiofemoral joint flexion. The patella tilts, rotates, and shifts medially in the initial stage of knee flexion and subsequently tilts, rotates, and shifts laterally. The finite patellar helical axis fluctuates near the femoral transepicondylar axis or posterior condylar axis. Moreover, factors affecting kinematics, such as morphology of the trochlear groove, soft tissue balance, and tibiofemoral motion, were analyzed. At the initial period of flexion, soft tissues play a vital role in adjusting patellar tracking, and during further flexion, the status of the patella is determined by the morphology of the trochlear groove and patellar facet. Our findings could increase our understanding of patellofemoral kinematics and can help to guide the operation plan for patients with patellofemoral pain syndrome.

Tibiofemoral kinematics in the transverse and frontal planes influence the location and magnitude of peak patella cartilage stress: An investigation of runners with and without patellofemoral pain

BACKGROUND

To determine whether the location and magnitude of peak patella cartilage stress varies among runners with and without patellofemoral pain. To determine whether tibiofemoral kinematics in the frontal and transverse planes predict peak lateral and medial patella cartilage stress.

METHODS

Twelve recreational runners with patellofemoral pain and 10 pain-free controls participated. Peak patella cartilage stress was quantified using finite element models that incorporated subject-specific kinematic and kinetic data obtained during running. Chi-square analysis was used to determine whether the location of peak patella cartilage stress (medial or lateral) varied between groups. Student's t-tests were used to determine whether the magnitude of peak medial and lateral patella cartilage stress varied between groups. In addition, stepwise regression analysis was performed to determine if tibiofemoral kinematics were predictive of peak medial and lateral cartilage stress.

FINDINGS

Among all subjects, 64% exhibited peak cartilage stress on the lateral patella facet. No group differences were found for the location and magnitude of peak cartilage stress on the medial or lateral facets. Tibiofemoral rotation in the transverse plane was the best predictor of peak lateral stress (45% of the variance, r = 0.67). Tibiofemoral rotation in the transverse plane was the best predictor of peak medial stress (44% of the variance, r = -0.67), followed by tibiofemoral rotation in the frontal plane (26% of the variance, r = 0.57).

INTERPRETATIONS

The location and magnitude of peak patella cartilage stress was similar among runners with and without patellofemoral pain. Tibiofemoral kinematics in the frontal and transverse planes are predictive of cartilage stress on the medial and lateral patella facets.

RESTORING KNEE EXTENSOR STRENGTH AFTER ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION: A CLINICAL COMMENTARY

One of the main priorities of rehabilitation after anterior cruciate ligament reconstruction (ACLR) surgery is the restoration of knee extensor muscle strength. Residual deficits in knee extensor muscle size and strength after injury are linked to poor biomechanics, reduced knee function, increased knee osteoarthritis risk, as well as heightened risk of re-injury upon return to sport. Most studies indicate that knee extensor muscle strength is typically not resolved prior to return to sport. This clinical commentary discusses strategies to optimize and accelerate the recovery of knee extensor strength post-surgery, with the purpose to support the clinician with evidence-based strategies to implement into clinical practice. Principally, two strategies exist to normalize quadriceps strength after surgery, 1) limiting strength loss after injury and surgery and 2) maximizing and accelerating the recovery of strength after surgery. Optimal preparation for surgery and a focused attempt to resolve arthrogenic muscle inhibition are essential in the pre and post-operative period prior to the inclusion of a periodized strength training program. Often voluntary strengthening alone is insufficient to fully restore knee extensor muscle strength and the use of electrical stimulation and where necessary the use of blood flow restriction training with low loads can support strength recovery, particularly in patients who are significantly load compromised and experience pain during exercise. Resistance training should employ all contraction modes, utilize open and closed kinetic chain exercise of both limbs, and progress from isolated to functional strength training, as part of a periodized approach to restoring neuromuscular function. Furthermore, thinking beyond the knee musculature and correcting core and hip dysfunction is also important to ensure an optimal knee extension strengthening program. The purpose of this clinical commentary is to provide a series of evidenced based strategies which can be implemented by clinicians responsible for the rehabilitation of patients after ACLR.

LEVEL OF EVIDENCE

5.

Regional Vastus Medialis and Vastus Lateralis Activation in Females with Patellofemoral Pain

INTRODUCTION

This study aimed to investigate whether regional activation patterns in the vasti muscles differ between females with and without patellofemoral pain (PFP), and whether muscle activation patterns correlate with knee extension strength.

METHODS

Thirty-six females with PFP and 20 pain-free controls performed a standardized knee flexion-extension task. The activation of vastus medialis (VM) and vastus lateralis (VL) was collected using high-density surface EMG and analyzed using principal component (PC) analysis. Spatial locations and temporal coefficients of the PC, and the percent variance they explain, were compared between groups and between the concentric and the eccentric phases of the movement. Correlations were assessed between PC features and knee extension strength.

RESULTS

The spatial weights of PC1 (general vasti activation) and PC2 (reflecting vastus-specific activation) were similar between groups (R > 0.95). Activation patterns in PFP were less complex than controls. Fewer PC features were necessary to reconstruct 90% of the signal for PFP participants in the concentric phase (P < 0.05), and the difference in bias of activation to VM (concentric phase) or VL (eccentric phase) was less between phases for PFP participants (P < 0.05). Smaller difference in vastus-specific activation in concentric and eccentric phases (less task specificity of VM/VL coordination) was related to greater maximal knee extension strength (P < 0.05, R < -0.43).

CONCLUSION

These data suggest PFP involves a simpler control strategy of VM and VL. The inverse association between task specificity and maximal knee extension strength suggests different presentations of PFP: lower knee extension strength but VM/VL coordination task specificity comparable with controls, or knee extension strength comparable with controls but lower VM/VL coordination task specificity.

Patella tracking calculation from patellofemoral positions at finite angles of knee flexion

Patellofemoral (PF) pain is a common knee disease. Patella tracking has a significant correlation with PF pain, therefore it could be used as an index for diagnosis and treatment evaluation. Previous research has proposed a method for measuring in vivo patella tracking by means of an interpolation algorithm. The present study aimed to quantify the effect of the interpolation parameters on the accuracy of the patella tracking with a motion capture experiment. The precise patella tracking of 5 knee specimens was collected and compared with the interpolated tracking. The results showed that the total interpolation error decreased to 2 mm with the number of interpolation angles increasing to 6. The number of interpolation reference points had a slight influence on the accuracy. The findings consolidated the feasibility of using interpolation to measure the in vivo patella tracking, and can help to optimize the accuracy and efficiency of the methodology.

Runners With Patellofemoral Pain Exhibit Greater Peak Patella Cartilage Stress Compared With Pain-Free Runners

The primary purpose of this study is to determine whether recreational runners with patellofemoral pain (PFP) exhibit greater peak patella cartilage stress compared with pain-free runners. A secondary purpose was to determine the kinematic and/or kinetic predictors of peak patella cartilage stress during running. A total of 22 female recreational runners (12 with PFP and 10 pain-free controls) participated in this study. Patella cartilage stress profiles were quantified using subject-specific finite element models simulating the maximum knee flexion angle during the stance phase of running. Input parameters to the finite element model included subject-specific patellofemoral joint geometry, quadriceps muscle forces, and lower-extremity kinematics in the frontal and transverse planes. Tibiofemoral joint kinematics and kinetics were quantified to determine the best predictor of stress using stepwise regression analysis. Compared with the pain-free runners, those with PFP exhibited greater peak hydrostatic pressure (PFP vs control: 21.2 [5.6] MPa vs 16.5 [4.6] MPa) and maximum shear stress (PFP vs control: 11.3 [4.6] MPa vs 8.7 [2.3] MPa). Knee external rotation was the best predictor of peak hydrostatic pressure and peak maximum shear stress (38% and 25% of variances, respectively), followed by the knee extensor moment (21% and 25% of variances, respectively). Runners with PFP exhibit greater peak patella cartilage stress during running compared with pain-free individuals. The combination of knee external rotation and a high knee extensor moment best predicted the elevated peak stress during running.

[Influence of lateral retinacular release on anterior knee pain following total knee arthroplasty]

Objective

To investigate the effect of lateral retinacular release on the clinical outcomes after total knee arthroplasty (TKA) without resurfacing of the patella.

Methods

A prospective randomized controlled study was performed on 132 patients with unilateral degenerative knee arthritis undergoing TKA bewteen October 2012 and October 2014, who met the selection criteria. During TKA, lateral retinacular release was used in 66 cases (trial group) and was not used in 66 cases (control group). Two patients were excluded from the study due to missing the follow-up in trial group. Four patients were excluded from the study due to lateral retinacular release in control group. Finally, 64 patients and 62 patients were included in the trial group and in the control group. There was no significant difference in gender, age, body mass index, side, disease duration, preoperative patellar morphology, grading of patellofemoral arthritis, grade of patellar cartilage degeneration, patellar malposition, patellar maltracking, patellar score, and Knee Society Score (KSS) between 2 groups ( P>0.05). The operation time, postoperative drainage volume, hospitalization time, postoperative complications, and patient satisfaction were recorded. Postoperative anterior knee pain was assessed by visual analogue scale (VAS), and the knee joint function was evaluated by KSS score and patellar score. The femoral angle, tibial angle, femoral flexion angle, and tibial posterior slope angle were measured on the X-ray film for postoperative prosthetic alignment. The postoperative patellar tracking and patellar position, as well as the presence of osteolysis, prosthesis loosening, patellar fracture and patellar necrosis were observed.

Results

All patients were followed up for 24 months. There was no significant difference in operation time, postoperative drainage volume, hospitalization time, and patient satisfaction between 2 groups ( P>0.05). The incidence of anterior knee pain in the trial group was better than that in the control group ( P=0.033). KSS score and patellar score were significantly improved in both groups at 24 months after operation when compared with preoperative scores ( P<0.05), but no significant difference was found between 2 groups ( P>0.05). Complications included hematoma (2 cases in the trial group, and 1 case in the control group), mild wound dehiscence (2 cases in each group respectively), skin-edge necrosis (1 case in the trial group), and superficial wound infection (1 case in each group respectively), which were cured by conservative treatment. No patellar necrosis, patella fracture, or knee lateral pain occurred in 2 groups. There was no significant difference in complication rate between groups ( P=0.392). Satisfactory implant alignment was observed in both groups during follow-up. There was no significant difference in femoral angle, tibial angle, femoral flexion angle, and tibial posterior slope angle between 2 groups ( P>0.05). No radiolucent line at the bone-implant interface was seen around the tibial components and femoral components in both groups. The patellar maltracking was observed in 3 patients of the trial group and 5 patients of the control group, showing no significant difference ( P=0.488). However, the incidence of patellar malposition in the trial group (18.8%) was significantly lower than that in the control group (35.5%) ( χ²=0.173, P=0.034).

Conclusion

Lateral retinacular release during primary TKA without resurfacing of the patella can reduce postoperative knee pain without increasing complications.

Sagittal plane tilting deformity of the patellofemoral joint: a new concept in patients with chondromalacia patella

PURPOSE

The aims of this study were to evaluate sagittal plane alignment in patients with chondromalacia patella via magnetic resonance imaging (MRI), analyse the relationships between the location of the patellar cartilaginous lesions and sagittal alignment and finally investigate the relationships between the sagittal plane malalignment and patellofemoral loadings using by finite element analysis.

METHODS

Fifty-one patients who were diagnosed with isolated modified Outerbridge grade 3-4 patellar chondromalacia based on MRI evaluation and 51 control subjects were evaluated. Chondromalacia patella patients were divided into three subgroups according to the chondral lesion location as superior, middle and inferior. The patella-patellar tendon angle (P-PT) was used for evaluation of sagittal alignment of patellofemoral joint. Each subgroup was compared with control group by using P-PT angle. To investigate the biomechanical effects of sagittal plane malpositioning on patellofemoral joint, bone models were created at 30°, 60° and 90° knee flexion by using mean P-PT angles, which obtained from patients with chondromalacia patellae and control subjects. The total loading and contact area values of the patellofemoral joints were investigated by finite element analysis.

RESULTS

The mean age of all participants was 52.9 ± 8.2 years. The mean P-PT angle was significantly lower in chondromalacia group (142.1° ± 3.6°) compared to control group (144.5° ± 5.3°) (p = 0.008). Chondral lesions were located in superior, middle and inferior zones in 16, 20 and 15 patients, respectively. The mean P-PT angles in patients with superior (141.8 ± 2.7) and inferior subgroups (139.2 ± 2.3) were significantly lower than the values in the control group (p < 0.05). The contact area values were detected higher in models with chondromalacia than in the control models at the same flexion degrees. There were increased loadings at 30° and 90° flexions in the sagittal patellar tilt models.

CONCLUSION

This study revealed that sagittal plain malpositioning of the patellofemoral joint might be related to chondromalacia, especially in the presence of lesions in the upper and lower part of the patella. This condition leads to supraphysiological loadings on the patellofemoral joint. Sagittal patellar tilt should be considered in the evaluation and management of patellar cartilage defects. Taking sagittal plane malalignment into consideration in patellofemoral joint evaluation will enable us to design new physical and surgical modalities.

LEVEL OF EVIDENCE

IV.

The Relationship of Static Tibial Tubercle-Trochlear Groove Measurement and Dynamic Patellar Tracking

BACKGROUND

The tibial tubercle to trochlear groove (TT-TG) distance is used for screening patients with a variety of patellofemoral joint disorders to determine who may benefit from patellar medialization using a tibial tubercle osteotomy. Clinically, the TT-TG distance is predominately based on static imaging with the knee in full extension; however, the predictive ability of this measure for dynamic patellar tracking patterns is unknown.

PURPOSE

To determine whether the static TT-TG distance can predict dynamic lateral displacement of the patella.

STUDY DESIGN

Cohort study (Diagnosis); Level of evidence, 2.

METHODS

The static TT-TG distance was measured at full extension for 70 skeletally mature subjects with (n = 32) and without (n = 38) patellofemoral pain. The dynamic patellar tracking patterns were assessed from approximately 45° to 0° of knee flexion by use of dynamic cine-phase contrast magnetic resonance imaging. For each subject, the value of dynamic lateral tracking corresponding to the exact knee angle measured in the static images for that subject was identified. Linear regression analysis determined the predictive ability of static TT-TG distance for dynamic patellar lateral displacement for each cohort.

RESULTS

The static TT-TG distance measured with the knee in full extension cannot accurately predict dynamic lateral displacement of the patella. There was weak predictive ability among subjects with patellofemoral pain ( r² = 0.18, P = .02) and no predictive capability among controls. Among subjects with patellofemoral pain and static TT-TG distances 15 mm or more, 8 of 13 subjects (62%) demonstrated neutral or medial patellar tracking patterns.

CONCLUSION

The static TT-TG distance cannot accurately predict dynamic lateral displacement of the patella. A large percentage of patients with patellofemoral pain and pathologically large TT-TG distances may have neutral to medial maltracking patterns.

Patellofemoral pain in athletes

Patellofemoral pain (PFP) is a frequent cause of anterior knee pain in athletes, which affects patients with and without structural patellofemoral joint (PFJ) damage. Most younger patients do not have any structural changes to the PFJ, such as an increased Q angle and a cartilage damage. This clinical entity is known as patellofemoral pain syndrome (PFPS). Older patients usually present with signs of patellofemoral osteoarthritis (PFOA). A key factor in PFPS development is dynamic valgus of the lower extremity, which leads to lateral patellar maltracking. Causes of dynamic valgus include weak hip muscles and rearfoot eversion with pes pronatus valgus. These factors can also be observed in patients with PFOA. The available evidence suggests that patients with PFP are best managed with a tailored, multimodal, nonoperative treatment program that includes short-term pain relief with nonsteroidal anti-inflammatory drugs (NSAIDs), passive correction of patellar maltracking with medially directed tape or braces, correction of the dynamic valgus with exercise programs that target the muscles of the lower extremity, hip, and trunk, and the use of foot orthoses in patients with additional foot abnormalities.

Patellofemoral Kinematics and Tibial Tuberosity-Trochlear Groove Distances in Female Adolescents With Patellofemoral Pain

BACKGROUND

Patellofemoral pain (PFP) is a prevalent disorder among female adolescents. Overuse is frequently cited as the cause of pain for this population. What is currently unclear, however, is if the patella demonstrates abnormal tracking patterns relative to the femoral trochlear groove in female adolescents with PFP.

PURPOSE

The aim of this case-control study was to determine if abnormal patellar tracking patterns are present in female adolescents with PFP. The secondary aim was to identify if an increased tibial tuberosity-trochlear groove (TT-TG) distance is associated with the observed kinematic patterns.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twenty female adolescent knees from 12 patients with PFP and 20 age-matched female knees from 13 healthy controls were recruited for this study. Patellofemoral kinematics (eg, lateral patellar displacement) during a repetitive knee extension-flexion maneuver was quantified by dynamic cine phase-contrast magnetic resonance imaging (MRI). Static MRI scans were used to determine the TT-TG distance.

RESULTS

Relative to the control cohort, female adolescents with PFP demonstrated significantly greater lateral displacement at 10° (3.2 mm; P < .001), 20° (2.3 mm; P < .001), and 30° (1.7 mm; P = .014) of knee flexion. A subgroup within this cohort (7 knees from 5 patients) demonstrated extreme lateral maltracking >2 SDs of the mean of the control cohort. This subgroup also demonstrated a greater TT-TG distance relative to the controls (Δ = 4.2 mm; P = .001).

CONCLUSION

This study demonstrates abnormal lateral patellar displacement in the absence of patellar tilt in female adolescents with PFP. Because all adolescents from both cohorts participated in impact sports, it appears that rigorous athletic training alone is inadequate to produce symptoms in this population. Rather, PFP may derive from a combination of physical activity in the context of pathological kinematics.

CLINICAL RELEVANCE

Abnormal patellar tracking patterns and abnormal static alignment have been shown to contribute to the etiology of patellofemoral pain in adults. This study demonstrates that pathologic patellar tracking patterns are present in adolescent females with patellofemoral pain.

Effects of tibial rotation on Ober's test and patellar tracking

BACKGROUND

The purpose of this study was to investigate the effects of tibial position on ITB flexibility and patellar position.

METHODS

A total of 31 asymptomatic subjects (21 males, 10 females) were recruited for this investigation. Adduction angle was measured by Ober's test, and PCD was measured by ultrasonography in three different tibial rotation conditions: N, IR, and ER.

RESULTS

Repeated measures ANOVA revealed a significant difference in adduction angle and PCD among three different tibial positions (P<0.05). Adduction angle was significantly greater in the N tibial position than in ER (P<0.05). The PCD was significantly greater in N position than in IR (P<0.05). However, the PCD was significantly smaller in IR compared with the N position (P<0.05).

CONCLUSIONS

These findings support that tibial rotation influences the flexibility of ITB and patellar positions. Therefore, excessive tibial rotation can cause inappropriate patellar positions that eventually lead to knee injury. Therapists should consider tibial rotation when measuring adduction angles because tibial rotation can change Ober's test results and contribute to the consistency of ITB length measurements.

LEVEL OF EVIDENCE

Level IV.

Quantitative analysis of dynamic patellar tracking in patients with lateral patellar instability using a simple video system

BACKGROUND

As patellar dislocation occurs during activity, it is more important to assess the behavior of the patellofemoral joint under dynamic conditions. The aim of this study was to compare patellar tracking between knees with and without patellar dislocation in patients with an unstable patella and healthy controls using a simple video technique.

METHODS

Twenty-three knees with patellar dislocation (dislocated group), 23 contralateral knees without dislocation (non-dislocated group), and 23 healthy knees (control group) were examined. Those with skin markers on anatomical landmarks were made to extend their knees actively, and skin markers were attached to the examiner's fingertips and the patella was followed by pinching. The knee during active knee extension was recorded with digital video cameras. The patella was tracked on imaging software, and the mediolateral patellar position (% patellar position: %PP) was calculated in reference to the knee width consecutively.

RESULTS

%PP was significantly different between the dislocated and control groups, from 30° (mean±SD: 58.9±6.2%, 54.6±4.7%) to 5° (64.2±5.2%, 55.2±5.2%). It was also significantly different between the non-dislocated and control groups, from 25° (58.9±7.1%, 54.5±4.6%) to 5° (63.8±6.5%, 55.2±5.2%). No significant difference in %PP was found between the dislocated and non-dislocated groups.

CONCLUSION

With the new video system, patellar tracking during active knee extension was successfully quantified. The tracking patterns were the same in knees with and without patellar dislocation, and the tracking in patients significantly differed from that in the controls at lower knee flexion angles.

CLINICAL RELEVANCE

The development of a quantitative examination technique for dynamic patellar tracking, which is easy to use and repeatedly applicable in a clinical situation, could help to follow-up the time-dependent changes and analyze the treatment effect on an unstable patella.

EFEITO DO TREINO NEUROMUSCULAR NA ROTAÇÃO DO JOELHO DURANTE A ATERRISSAGEM EM MULHERES

Introdução: O grande índice de lesões do ligamento cruzado anterior sem envolver contato em mulheres é motivo de curiosidade entre os cientistas, pois avaliações de aterrissagem podem sugerir a predisposição ao risco dessa lesão. Neste sentido, vários protocolos de treinamento foram utilizados como intervenção e obtiveram resultados diversificados na alteração desse fator de risco. Objetivo: O objetivo deste projeto foi avaliar as possíveis alterações de rotação do joelho na aterrissagem unipodal após a intervenção de um programa de treinamento neuromuscular. Métodos: Participaram do estudo 18 mulheres com idade entre 18 e 51 anos, que foram distribuídas em dois grupos: grupo de treinamento neuromuscular de oito semanas (GTN) (n = 11) e grupo controle (GC) (n = 7). Além disso, não apresentavam lesão musculoesquelética ou dores nos membros inferiores. Cada participante realizou cinco aterrissagens unipodais válidas de uma plataforma de 40 cm de altura. O processo de captura de movimento foi realizado com 12 câmeras infravermelho do sistema OptiTrack(tm) para obter as coordenadas tridimensionais de marcadores fixados nos pontos anatômicos de interesse. Os sistemas de coordenadas locais da coxa e da perna foram definidos por meio dos respectivos marcadores fixados nos pontos anatômicos. Dessa forma, foram calculados os ângulos de rotação do joelho nos planos sagital, frontal e transverso através das sequências dos ângulos de Euler e as velocidades angulares através das formulações dos quatérnions. Resultados: Os resultados mostraram que houve um aumento na velocidade de rotação do joelho após o treinamento neuromuscular. Conclusão: Conclui-se que o treinamento neuromuscular resultou em maior velocidade de rotação no joelho nos 40 milissegundos que sucedem a aterrissagem unipodal.

Effect of leg press training on patellar realignment in patients with patellofemoral pain

[Purpose] The purpose of this study was to investigate the effect of leg press and leg press with hip adduction exercise training on patellar alignment and pain in patients with patellofemoral pain (PFP). [Subjects and Methods] Seventeen patients participated in this study. Eight weeks of leg press or leg press with hip adduction training, including progressive lower-limb weight-training and stretching, was given. Patellar alignment (tilt and displacement) and pain measurements were conducted before and after leg press or leg press with hip adduction training. Patellar tilt angle and the bisect offset index were measured on axial computed tomography scans of the fully extended knee position with the quadriceps relaxed and contracted. Pain was assessed by using a 10-cm visual analog scale. [Results] No differences were found in patellar tilt and displacement with the quadriceps either relaxed or contracted after leg press and leg press with hip adduction. However, significant pain reduction was evident in both leg press and leg press with hip adduction. [Conclusion] The results indicated that patellar realignment does not appear to mediate pain alleviation. Furthermore, hip adduction in addition to leg press training had no additive beneficial effect on patellar realignment or pain reduction.

Evaluating the potential synergistic benefit of a realignment brace on patients receiving exercise therapy for patellofemoral pain syndrome: a randomized clinical trial

BACKGROUND

It has been previously shown that exercise programs for patellofemoral pain syndrome (PFPS) can be supported by medially directed taping. Evidence supporting the use of patellar braces is limited because previous studies have been low quality. The aim of this study is to compare the outcomes of patients with PFPS after treatment with a medially directed patellar realignment brace and supervised exercise.

METHODS

In a prospective randomized multicenter trial, 156 patients with PFPS were included and randomly assigned to 6 weeks of supervised physiotherapy in combination with the patellar realignment brace, or supervised physiotherapy alone. Outcome measures were the Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales, numeric analog pain scores, and the Kujala score at baseline, 6 weeks, 3 months, and 1 year after the start of therapy. The patient's self-reported perception of recovery was also assessed at these points.

RESULTS

Both treatment groups showed a significant improvement in all outcome measures over the study period. After 6 and 12 weeks of therapy, patients in the brace group had significantly higher KOOS sub-scale scores, a higher mean Kujala score, and less pain while climbing stairs or playing sports. After 54 weeks a group difference could be only detected for the KOOS ADL sub-scale.

CONCLUSION

The use of a medially directed realignment brace leads to better outcomes in patients with PFPS than exercise alone after 6 and 12 weeks of treatment. After 1 year of follow-up this positive effect diminished.

Effects of Off-Axis Elliptical Training on Reducing Pain and Improving Knee Function in Individuals With Patellofemoral Pain

OBJECTIVE

To examine whether an off-axis elliptical training program reduces pain and improves knee function in individuals with patellofemoral pain (PFP).

DESIGN

Controlled laboratory study, pretest-posttest.

SETTING

University rehabilitation center.

PARTICIPANTS

Twelve adult subjects with PFP.

INTERVENTIONS

Subjects with PFP completed an exercise program consisting of 18 sessions of lower extremity off-axis training using a custom-made elliptical trainer that allows frontal plane sliding and transverse plane pivoting of the footplates.

MAIN OUTCOME MEASURES

Changes in knee pain and function posttraining and 6 weeks after training were evaluated using the Knee Injury and Osteoarthritis Outcome Score (KOOS) and International Knee Documentation Committee (IKDC) scores. Lower extremity off-axis control was assessed by pivoting and sliding instability, calculated as the root mean square (RMS) of the footplate pivoting angle and sliding distance during elliptical exercise. Subjects' single-leg hop distance and proprioception in detecting lower extremity pivoting motion were also evaluated.

RESULTS

Subjects reported significantly greater KOOS and IKDC scores (increased by 12-18 points) and hop distance (increased by 0.2 m) after training. A significant decrease in the pivoting and sliding RMS was also observed after training. Additionally, subjects with PFP demonstrated improved pivoting proprioception when tested under a minimum weight-bearing position.

CONCLUSIONS

An off-axis elliptical training program was effective in enhancing lower extremity neuromuscular control on the frontal and transverse planes, reducing pain, and improving knee function in persons with PFP.

CLINICAL RELEVANCE

This study provides a novel intervention approach to enhance the control of the frontal and transverse plane motions of the lower extremities during functional weight-bearing activities. This novel off-axis elliptical training may be incorporated with other common treatment options currently available for PFP to augment the effects of musculoskeletal rehabilitation for the PFP population.

MRI-based analysis of patellofemoral cartilage contact, thickness, and alignment in extension, and during moderate and deep flexion

BACKGROUND

Several factors are believed to contribute to patellofemoral joint function throughout knee flexion including patellofemoral (PF) kinematics, contact, and bone morphology. However, data evaluating the PF joint in this highly flexed state have been limited. Therefore, the purpose of this study was to evaluate patellofemoral contact and alignment in low (0°), moderate (60°), and deep (140°) knee flexion, and then correlate these parameters to each other, as well as to femoral morphology.

METHODS

Sagittal magnetic resonance images were acquired on 14 healthy female adult knees (RSRB approved) using a 1.5 T scanner with the knee in full extension, mid-flexion, and deep flexion. The patellofemoral cartilage contact area, lateral contact displacement (LCD), cartilage thickness, and lateral patellar displacement (LPD) throughout flexion were defined. Intra- and inter-rater repeatability measures were determined. Correlations between patellofemoral contact parameters, alignment, and sulcus morphology were calculated.

RESULTS

Measurement repeatability ICCs ranged from 0.94 to 0.99. Patellofemoral cartilage contact area and thickness, LCD, and LPD were statistically different throughout all levels of flexion (p<0.001). The cartilage contact area was correlated to LPD, cartilage thickness, sulcus angle, and epicondylar width (r=0.47-0.72, p<0.05).

DISCUSSION

This study provides a comprehensive analysis of the patellofemoral joint throughout its range of motion.

CONCLUSIONS

This study agrees with past studies that investigated patellofemoral measures at a single flexion angle, and provides new insights into the relationship between patellofemoral contact and alignment at multiple flexion angles.

CLINICAL RELEVANCE

The study provides a detailed analysis of the patellofemoral joint in vivo, and demonstrates the feasibility of using standard clinical magnetic resonance imaging scanners to image the knee joint in deep flexion.

Proximal muscle rehabilitation is effective for patellofemoral pain: a systematic review with meta-analysis

BACKGROUND

Proximal muscle rehabilitation is commonly prescribed to address muscle strength and function deficits in individuals with patellofemoral pain (PFP). This review (1) evaluates the efficacy of proximal musculature rehabilitation for patients with PFP; (2) compares the efficacy of various rehabilitation protocols; and (3) identifies potential biomechanical mechanisms of effect in order to optimise outcomes from proximal rehabilitation in this problematic patient group.

METHODS

Web of Knowledge, CINAHL, EMBASE and Medline databases were searched in December 2014 for randomised clinical trials and cohort studies evaluating proximal rehabilitation for PFP. Quality assessment was performed by two independent reviewers. Effect size calculations using standard mean differences and 95% CIs were calculated for each comparison.

RESULTS

14 studies were identified, seven of high quality. Strong evidence indicated proximal combined with quadriceps rehabilitation decreased pain and improved function in the short term, with moderate evidence for medium-term outcomes. Moderate evidence indicated that proximal when compared with quadriceps rehabilitation decreased pain in the short-term and medium-term, and improved function in the medium term. Limited evidence indicated proximal combined with quadriceps rehabilitation decreased pain more than quadriceps rehabilitation in the long term. Very limited short-term mechanistic evidence indicated proximal rehabilitation compared with no intervention decreased pain, improved function, increased isometric hip strength and decreased knee valgum variability while running.

CONCLUSIONS

A robust body of work shows proximal rehabilitation for PFP should be included in conservative management. Importantly, greater pain reduction and improved function at 1 year highlight the long-term value of proximal combined with quadriceps rehabilitation for PFP.

Effects of Kinesio Taping versus McConnell Taping for Patellofemoral Pain Syndrome: A Systematic Review and Meta-Analysis

Objectives. To conduct a systematic review comparing the effects of Kinesio taping with McConnell taping as a method of conservative management of patients with patellofemoral pain syndrome (PFPS). Methods. MEDLINE, PUBMED, EMBASE, AMED, and the Cochrane Central Register of Control Trials electronic databases were searched through July 2014. Controlled studies evaluating the effects of Kinesio or McConnell taping in PFPS patients were retrieved. Results. Ninety-one articles were selected from the articles that were retrieved from the databases, and 11 articles were included in the analysis. The methods, evaluations, and results of the articles were collected, and the outcomes of patellar tapings were analyzed. Kinesio taping can reduce pain and increase the muscular flexibility of PFPS patients, and McConnell taping also had effect in pain relief and patellar alignment. Meta-analysis showed small effect in pain reduction and motor function improvement and moderate effect in muscle activity change among PFPS patients using Kinesio taping. Conclusions. Kinesio taping technique used for muscles can relieve pain but cannot change patellar alignment, unlike McConnell taping. Both patellar tapings are used differently for PFPS patients and substantially improve muscle activity, motor function, and quality of life.

Sagittal plane evaluation of patellofemoral movement in patellofemoral pain patients with no evidence of maltracking

PURPOSE

The cause of abnormal patellar kinematics in patients with patellofemoral pain remains unclear. Many patients who develop patellofemoral pain symptoms do not exhibit evidence of maltracking. In these patients, sagittal plane evaluation of patellofemoral movement should be performed.

METHODS

Knee radiographs were obtained for forty healthy volunteers and thirty patients at 0°, 30°, 60°, 90° and 120° of flexion in a standing weight-bearing position. The degree of active patellar movement was measured by a newly developed technique called "patellar motion angle". Three independent examiners sequentially performed all of the measurements under identical conditions.

RESULTS

A significant decrease in the patellar motion angle was found during deep knee flexion from 90° to 120° in the patient group compared to the volunteer group (mean 18.5° ± 5.8° and 23.6° ± 6.2°, respectively) (P = 0.001). From 0° to 90° of knee flexion, no significant differences in the patellar motion angle were found between the two groups.

CONCLUSION

Sagittal plane patellofemoral joint kinematics is an area of interest in the study of the mechanical factors associated with patellofemoral pain. This study demonstrated a decrease in patellar movement during deep knee bending activity in patients with patellofemoral pain.

LEVEL OF EVIDENCE

Therapeutic study, Level II.

Patellofemoral kinematics during deep knee flexion after total knee replacement: a computational simulation

PURPOSE

Actions requiring deep knee flexion, such as kneeling and squatting, are challenging to perform after total knee replacement (TKR), though many manufactures emphasize that their knee prostheses could safely achieve high flexion. Little is known about the patellofemoral kinematics during deep flexion. This study aimed to track the movement of the patella during kneeling and squatting through dynamic computational simulation.

METHODS

A validated knee model was used to analyse the patellar kinematics after TKR, including shifting, tilting and rotation. The data were captured from full extension to 135° of knee flexion. For kneeling, an anterior force of 500 N was applied perpendicularly on the tibial tubercle as the knee flexed from 90° to 135°. For squatting, a ground reaction force was applied through the tibia from full extension to 135° of flexion.

RESULTS

This study found that patellar shifting and rotation in kneeling were similar to those while squatting. However, during kneeling, the patella had a greater medial tilt and showed signs of abrupt patellar tilt owning to an external force being concentrated on the tibial tubercle.

CONCLUSIONS

In terms of squatting and kneeling movements, the latter is a more strenuous action for the patellofemoral joint after TKR due to the high forces acting on the tibial tubercle. It is suggested that overweight patients or those requiring high flexion should try to avoid kneeling to reduce the risk of the polyethylene wear. Further modification of trochlear geometry may be required to accommodate abrupt changes in patellar tilting.

LEVEL OF EVIDENCE

II.

Re-evaluating the functional implications of the Q-angle and its relationship to in-vivo patellofemoral kinematics

BACKGROUND

The Q-angle is widely used clinically to evaluate individuals with anterior knee pain. Recent studies have questioned the utility of this measure and have suggested that a large Q-angle may not be associated with lateral patellofemoral translation, as often assumed. The objective of this study was to determine: 1) how accurately the Q-angle represents the line-of-action of the quadriceps and 2) if adding active quadriceps contraction or a bent knee position to the measurement of the Q-angle improves its reliability, accuracy, and association with patellofemoral kinematics.

METHODS

The study included individuals diagnosed with chronic idiopathic patellofemoral pain and control subjects (n=43 and n=30 knees). Three measures of the clinical Q-angle (straight- and bent-knee with relaxed quadriceps and straight-knee with maximum isometric quadriceps contraction) were obtained with a goniometer and compared to a fourth MR-based measure of Q-angle. Patellofemoral kinematics were derived from dynamic cine-phase contrast images, acquired while subjects extended/flexed their knee from approximately 0° and 45°.

FINDINGS

The Q-angle did not represent the line-of-action of the quadriceps. The average difference between each clinical and the MR-based Q-angle ranged from 5° to 8°. These differences varied greatly across subjects (range: -28.5° to 3.9(o)). Adding an active quadriceps contraction or a bent knee position, did not improve the reliability of the Q-angle. An increased Q-angle correlated to medial patellar displacement and tilt (r=0.38-0.54, P<0.001) in the cohort with anterior knee pain.

INTERPRETATION

Clinicians are cautioned against using the Q-angle to infer patellofemoral kinematics.

Normative data of frontal plane patellar alignment in athletes

OBJECTIVE

The objective of this study was to provide normative data of frontal plane patellar alignment according to McConnell and Arno angles, verify the association between theses angles and identify the presence of patellar rotation in different sports.

DESIGN

Cross-sectional.

PARTICIPANTS

Nine participants (18 knees) were assessed in a preliminary study to verify the intra and inter-examiner reliabilities of the patellar alignment measures. In the main study, 230 volleyball, basketball, gymnastics and soccer athletes (460 knees) were evaluated in order to obtain normative data of patellar alignment.

MAIN OUTCOME MEASURES

Frontal plane patellar alignment (McConnell and Arno angles) measured in standing position by means of photogrammetry.

RESULTS

The standardized method demonstrated intra and inter-examiner reliability coefficients varying from .85 to .98. The mean McConnell and Arno angles were 2.05° (±5.9) and 2.89° (±7.57), respectively. A low association was observed (r = .189, p < .0001) between these angles. There was a difference in distribution of medial and lateral rotations, according to the McConnell angle, between different sports (p < .014).

CONCLUSIONS

The proposed procedure for measuring patellar alignment according to McConnell and Arno angles proved to be highly reliable. This made possible the establishment of normative data in a large sample of healthy athletes.

The effect of ground tilt on the lower extremity muscle activity of stroke patients performing squat exercises

[Purpose] The purpose of this study was to determine the effect of ground tilt on the lower extremity muscle activity of stroke patients performing squat exercises. [Subjects] Fifteen hemiparetic patients volunteered to participate in this study. [Methods] The subjects performed squat exercises at three different ground tilt angles: 15° plantar flexion, a neutral position, and 15° dorsiflexion. A surface electromyogram (sEMG) was used to record the electromyographic activities of the leg extensor muscle in the vastus lateralis (VL), vastus medialis (VM), gastrocnemius lateralis (GL), and gastrocnemius medialis (GM). The sEMG activity was analyzed using a one-way repeated measures ANOVA and a post hoc Bonferroni correction. [Results] The results of this study are summarized as follows. Significant differences were noted for the VL and the GL when the angle of the ankle joint was between the 15° plantar flexion and neutral positions during squat exercises involving the VL and when the angle of the ankle joint was between the neutral position and 15° dorsiflexion during squat exercises involving the VM. [Conclusion] In this study, sEMG showed that the VL and GL changed significantly during squat exercises according to the ground tilt angle of hemiparetic patients. Therefore, squat exercises with different ground tilt angles can be used to improve VL and GL strength.