Histologic retinacular changes associated with ischemia in painful patellofemoral malalignment

Physiopathology of patello-femoral osteoarthritis: current concepts

Patellofemoral osteoarthritis (PFOA) is the result of degeneration and loss of articular cartilage of the patella and trochlea, and is a common cause of anterior knee pain. PFOA is triggered by insufficient adaptation to overload of the articular cartilage of the PF joint created by abnormal biomechanics. It is important to understand the pathophysiology and natural history to make the diagnosis and to plan treatment. Innate factors including malalignment, patellar instability, kinematic disorders, and acquired factors like trauma, obesity, and endocrine diseases have been found to be causes of PFOA. Genetic predisposition is also described as a contributing cause but without much scientific evidence. The diagnosis will be based on clinical manifestations, such as anterior knee pain aggravated by overloading activities, identification of risk factors, and exclusion of referred pain from other pathologies, followed by a systematic and structured physical examination. Imaging will be useful for assessing the presence of early osteoarthritis in the other compartments, for classification of the PFOA, and to identify features to establish an adequate treatment. This paper discusses varying management options for different causes of patellofemoral disease and explains the complexity of the PF joint and its often poorly understood biomechanics.

Impaired hemodynamics of the patella in patients with patellofemoral pain: A case-control study

Purpose

According to the homeostasis model, patellofemoral pain (PFP) arises as a consequence of disturbed homeostasis of anterior structures of the knee due to vascular insufficiency. Near-infrared spectroscopy (NIRS) allows to measure changes of concentrations (µmol/cm2) of (de)-oxygenated hemoglobine (HHb and O2Hb). The aim was to study differences in patellar hemodynamics between patients and healthy controls.

Methods

Hemodynamics of patients (n = 30 [female = 20, age = 21.5, BMI = 22.9]) and controls (n = 30 (female = 18, age = 21.4, BMI = 22.4]) were evaluated for two activities ('Prolonged Sitting' and 'Stair Descent'). Blinding for health status was implemented.

Results

During 'Prolonged Sitting', PFP patients exhibited smaller decreases in mean changes for HHb (PFP [M = -1.5 to -1.9], healthy controls [M = -2.0 to -2.3]) and O2Hb (PFP [M = -2.0 to -3.2], healthy controls [M = -3.4 to -4.1]). However, these differences were statistically non-significant (p = 0.14-0.82 and p = 0.056-0.18, respectively). Conversely, for 'Stair Descent', PFP patients showed statistically significant smaller decreases in mean changes for HHb (PFP [M = -1.9, SD = 1.8], healthy controls [M = -2.5, SD = 1.7], p = 0.043) and O2Hb (PFP [M = -3.2, SD = 3.2], healthy controls [M = -4.9, SD = 2.7], p = 0.004).

Conclusions

The differences suggest potential impairment in patellar hemodynamics in PFP patients, providing support for the homeostasis model. Evidence-based treatment strategies targeting patellar hemodynamics should be further refined and subjected to evaluation in clinical trials.

Level of Evidence

Level III.

Near-Infrared Spectroscopy measurements are reliable for studying patellar bone hemodynamics and affected by venous occlusion, but not by skin compression

PURPOSE

According to the homeostasis model, patellofemoral pain (PFP) results from disturbed homeostasis due to vascular insufficiency in the anterior knee. Near-Infrared Spectroscopy (NIRS) measures relative changes in concentrations (in µmol/cm2) of (de-)oxygenated hemoglobine (HHb and O2Hb). The aims were to: 1) investigate the characteristics of the NIRS signal derived from the patella during experiments affecting hemodynamics in healthy controls, and 2) determine the test-retest reliability of NIRS in positions clinically relevant for PFP patients.

METHODS

Two experiments were conducted on 10 healthy controls and analysed using Student's t-test. Reliability (ICC2,1) was evaluated for two activities ('Prolonged Sitting' and 'Stair Descent') in five PFP patients and 15 healthy controls, performed twice within five days.

RESULTS

The NIRS signal (HHb and O2Hb) showed a statistically significant increase (p < .001 - .002) on all optodes (30, 35, 40 mm) during 'Venous Occlusion' (M = 1.0 - 2.0), while it showed no statistically significant change (p = .075 - .61) during 'Skin Compression' (M = -0.9 - 0.9) on the 30 and 35 mm optode. Reliability of NIRS (HHb and O2Hb) ranged from moderate to almost perfect (ICC2,1 = .47 - .95) on the 30 mm optode for 'Prolonged Sitting', and from moderate to substantial (ICC2,1 = .50 - .68) on the 35 mm optode for 'Stair Descent'.

CONCLUSIONS

Patella NIRS measurements are affected by venous occlusion, but not by skin compression, and are sufficiently reliable as research application to compare real-time patellar bone hemodynamics. These insights may assist to improve effectiveness of evidence-based treatment strategies for PFP.

TRIAL REGISTRATION

ISRCTN Trial Registration under number: 90377123.

The influence of iliotibial tract thickness on clinical outcomes in women with patellofemoral pain

BACKGROUND

The assessment of iliotibial tract thickness by ultrasonography may help identify a key, previously unexplored factor that may contribute directly to the homeostasis imbalance of the femoropatellar joint in people with patellofemoral pain (PFP).

OBJECTIVES

To compare the iliotibial tract thickness of people with PFP and asymptomatic people; and to correlate the iliotibial tract thickness with self-reported pain and function of people with PFP.

METHODS

Eighty women, separated into two groups: PFP group (n = 40) and control group consisting of asymptomatic participants (CG; n = 40). The participants answered the Anterior Knee Pain Scale (AKPS) questionnaire, to identify the self-reported knee function; they evaluated the pain in millimeters by the Visual Analog Scale for pain (VAS). For the imaging evaluation, an ultrasound was used, with a linear transducer at the distal portion of the iliotibial tract (coronal plane), with the participants positioned in dorsal decubitus, with 20° of knee flexion. The iliotibial band was visualized in its long axis, and three sequential images were recorded between the lateral femoral condyle and the lateral tibial condyle. The measurements were normalized and correlated.

RESULTS

The groups had no differences (P > 0.001) between participants for: age/weight/height/IMC. Participants in the PFP group had moderate levels of pain (58 + 2.1 mm), considerable self-reported functional limitation (d = 3.05) and greater iliotibial tract thickness compared with the CG (d = 2.41).

CONCLUSION

The iliotibial tract of women diagnosed with PFP have greater thickness compared with asymptomatic women. There was no association between iliotibial tract thickness and subjective measures of pain and function.

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.

Blood perfusion of patellar bone measured by dynamic contrast-enhanced MRI in patients with patellofemoral pain: A case-control study

BACKGROUND

Altered perfusion might play an important role in the pathophysiology of patellofemoral pain (PFP), a common knee complaint with unclear pathophysiology.

PURPOSE

To investigate differences in dynamic contrast-enhanced (DCE)-MRI perfusion parameters between patients with PFP and healthy control subjects.

POPULATION/SUBJECTS/PHANTOM/SPECIMEN/ANIMAL MODEL

Thirty-five adult patients with PFP and 44 healthy adult control subjects.

FIELD STRENGTH/SEQUENCE

3T DCE-MRI consisting of a sagittal, anterior-posterior, frequency-encoded, fat-suppressed 3D spoiled gradient-echo sequence with intravenous contrast administration.

ASSESSMENT

Patellar bone volumes of interest (VOIs) were delineated by a blinded observer. Quantitative perfusion parameters (k_ep and k_trans ) were calculated from motion-compensated DCE-MRI data by fitting Tofts' model. Weighted mean and unweighted median values of k_ep and k_trans were computed within the patellar bone VOIs.

STATISTICAL TESTS

Differences in patellar bone perfusion parameters were compared between groups by linear regression analyses, adjusted for confounders.

RESULTS

Mean differences of weighted mean and unweighted median were 0.0039 (95% confidence interval [CI] -0.0013; 0.0091) and 0.0052 (95% CI -0.0078; 0.018) for k_trans , and 0.046 (95% CI -0.021; 0.11) and 0.069 (95% CI -0.017; 0.15) for k_ep , respectively. All perfusion parameters were not significantly different between groups (P-values: 0.32; 0.47 for k_trans , and 0.24; 0.15) for k_ep . However, a significant difference in variance between populations was observed for k_trans (P-value 0.007).

DATA CONCLUSION

Higher patellar bone perfusion parameters were found in patients with PFP when compared to healthy control subjects, but these differences were not statistically significant. This result, and the observed significant difference in k_trans variance, warrant further research.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;47:1344-1350.

Holistic approach to understanding anterior knee pain. Clinical implications

Anterior knee pain is one of the most frequent reasons for consultation within knee conditions. The aetiology is not well known, which explains the sometimes unpredictable results of its treatment. Normally, when we see a patient in the office with anterior knee pain, we only study and focus on the knee. If we do this, we are making a big mistake. We must not forget to evaluate the pelvis and proximal femur, as well as the psychological factors that modulate the course of the illness. Both the pelvifemoral dysfunction as well as the psychological factors (anxiety, depression, catastrophization and kinesiophobia) must be included in our therapeutic targets of the multidisciplinary treatment of anterior knee pain. We must not only focus on the knee, we must remember to "look up" to fully understand what is happening and be able to solve this difficult problem. The aetiology of anterior knee pain is multifactorial. Therefore, diagnosis and treatment of patellofemoral disorders must be individualized. Our findings stress the importance of tailoring physiotherapy, surgery and psycho-educational interventions to each patient.

Correlation between Intrinsic Patellofemoral Pain Syndrome in Young Adults and Lower Extremity Biomechanics

[Purpose] The purpose of this study was to evaluate the correlation between intrinsic patellofemoral pain syndrome (PFPS) in young adults and lower extremity biomechanics. [Subjects] This experiment was carried out with sixty (24 men and 32 women), who are normal university students as subjects. [Methods] All subjects underwent 3 clinical evaluations. For distinguishing the intrinsic PFPS from controls, we used the Modified Functional Index Questionnaire (MFIQ), Clarke’s test and the Eccentric step test. Based on the results of the tests, subjects who were classified as positive for 2 more tests were allocated to the bilateral or unilateral intrinsic PFPS group (n=14), and the others were allocated to the control group (n=42). These two groups were tested for hamstring tightness, foot overpronation, and static Q-angle and dynamic Q-angle. These are the four lower extremity biomechanic, cited as risk factors of patellofemoral pain syndrome. [Results] The over pronation, static Q-angle and the dynamic Q-angle were not significantly different between the two groups. However, the hamstring tightness of the PFPS group was significantly greater than that of the controls. [Conclusion] We examined individuals for intrinsic patellofemoral pain syndrome in young adults and lower extremity biomechanics. We found a strong correlation between intrinsic PFPS and hamstring tightness.

Phenomenon of painless knee in recurrent patellar dislocation in children

INTRODUCTION

Cartilage lesion with patellar malalignment may be correlated with pain. Situations in which patients with recurrent patellar dislocation are painless between episodes of luxation can be approached with considerable curiosity. We evaluated the distribution of substance-P and S-100 protein expression in soft tissue of the knee in children with recurrent patellar dislocation, in order to evaluate the distribution of nociceptors and determine tissue origins of this situation.

MATERIAL AND METHODS

Samples were collected from the medial and lateral synovial membrane, medial and lateral patellar retinaculum, Hoffa's body, patellar ligament, and quadriceps' aponeurosis in 10 children during the Blauth procedure and 10 adults with idiopathic osteoarthritis during total joint alloplasty. The density of nociceptive fibres was compared in the children and adults using S-100 and substance-P monoclonal antibodies.

RESULTS

Statistical differences between groups were demonstrated for S-100 expression in synovial membrane of the medial knee compartment (p < 0.05) and for substance-P expression in the medial patellar retinaculum (p < 0.05) and synovial membrane of the lateral (p < 0.05) and medial (p < 0.05) knee compartment in favour of children.

CONCLUSIONS

Lack of pain sensations in patients with recurrent patellar dislocation may be associated with non-increased expression of nerve endings in Hoffa's body. Increased expression of either S-100 protein or substance-P in synovial membrane and the medial retinaculum did not induce pain development in the knee joints of that group of patients.

Patellofemoral pain: proximal, distal, and local factors, 2nd International Research Retreat

Patellofemoral pain (PFP) is one of the most common lower extremity conditions seen in orthopaedic practice. The mission of the second International Patellofemoral Pain Research Retreat was to bring together scientists and clinicians from around the world who are conducting research aimed at understanding the factors that contribute to the development and, consequently, the treatment of PFP. The format of the 2.5-day retreat included 2 keynote presentations, interspersed with 6 podium and 4 poster sessions. An important element of the retreat was the development of consensus statements that summarized the state of the research in each of the 4 presentation categories. In this supplement, you will find the consensus documents from the meeting, as well as the keynote addresses, schedule, and platform and poster presentation abstracts.

[Patellofemoral pain]

We review the current status of knowledge in the field of pathogenesis of anterior knee pain in the young patient. Emphasis is placed on newer findings. We have developed what we call the "neural model" as an explanation for the genesis of anterior knee pain. According to our studies we hypothesize that periodic short episodes of ischemia in the lateral retinaculum could be implicated in the pathogenesis of anterior knee pain by triggering neural proliferation of nociceptive axons (substance P-positive nerves), mainly in a perivascular location. Our findings are compatible with the tissue homeostasis theory widely accepted currently to explain the genesis of anterior knee pain.

Patellofemoral pain syndrome provides a challenge to evidence-based practice

Physiotherapists in musculoskeletal out-patients' will be wellaccustomed to the large number of patients with patellofemoral pain syndrome (PFPS). The need for effective, evidence-based treatment with this patient group is vital, and it is the chasm between the plethora of literature and the reality of clinical practice that this editorial will explore.

Decreased pulsatile blood flow in the patella in patellofemoral pain syndrome

BACKGROUND

Anterior knee pain without clinical and radiologic abnormalities has primarily been explained from a purely structural view. A recently proposed biologic and homeostatic explanation questions the malalignment theory. No objective measurement of the pathophysiology responsible for changes in local homeostasis has been presented.

HYPOTHESIS

Flexing the knee joint interferes with the perfusion of the patellar bone in patellofemoral pain syndrome.

STUDY DESIGN

Case control study; Level of evidence, 4.

METHODS

Pulsatile blood flow in the patella was measured continuously and noninvasively using photoplethysmography. Measurements were made with the patient in a resting position with knee flexion of 20 degrees and after passive knee flexion to 90 degrees. In total, 22 patients with patellofemoral pain syndrome were examined bilaterally, and 33 subjects with healthy knees served as controls.

RESULTS

The pulsatile blood flow in the patient group decreased after passive knee flexion from 20 degrees to 90 degrees (systematic change in position, or relative position [RP] = -0.32; 95% confidence interval for RP, -0.48 to -0.17), while the response in the control group showed no distinct pattern (RP = 0.17; 95% confidence interval for RP, -0.05 to 0.31). The difference between the groups was significant (P = .0002). The median change in patients was -26% (interquartile range, 37).

CONCLUSIONS

Pulsatile patellar blood flow in patellofemoral pain syndrome patients is markedly reduced when the knee is being flexed, which supports the previous notion of an ischemic mechanism involved in the pathogenesis of this pain syndrome.