Does patella lowering as part of multilevel surgery improve knee kinematics in children with cerebral palsy and crouch gait? A meta-analysis of comparative studies

Purpose

To evaluate differences in knee kinematic outcomes of patellar-lowering surgery, specifically patellar tendon advancement or patellar tendon shortening, compared with no-patellar-lowering surgery in multilevel surgery for children with cerebral palsy and crouch gait.

Methods

Four databases were searched to retrieve studies published from inception until 2023. Three reviewers independently screened for studies with observational or randomized control designs, comparing two groups of patients with cerebral palsy and crouch gait who underwent multilevel surgery (with patellar-lowering surgery versus no-patellar-lowering surgery), where various gait analysis outcomes were reported (CRD42023450692). The risk of bias was assessed with the Risk Of Bias In Non-randomised Studies - of Interventions (ROBINS-I) tool.

Results

Seven studies (249 patients and 368 limbs) met the eligibility criteria. Patients undergoing patellar-lowering surgery demonstrated statistically significant improvements in knee flexion at initial contact (mean difference = -6.39; 95% confidence interval = [-10.4, -2.75]; p = 0.0006; I2 = 84%), minimum knee flexion in stance (mean difference = -14.27; 95% confidence interval = [-18.31, -10.23]; p < 0.00001; I2 = 89%), and clinical knee flexion contracture (mean difference = -5.6; 95% confidence interval = [-9.59, -1.6]; p = 0.006; I2 = 95%), with a significant increase in anterior pelvic tilt (mean difference = 2.97; 95% confidence interval = [0.58, 5.36]; p = 0.01; I2 = 15%). However, improvements in gait deviation index and decrease in peak knee flexion in swing did not reach statistical significance. Subgroup analysis reduced heterogeneity and revealed (1) greater improvement using patellar tendon shortening versus patellar tendon advancement techniques; (2) lack of knee flexion contracture improvement in high-quality or longer-term studies; (3) longer-term improvement only in minimum knee flexion in stance, with a decrease in peak knee flexion in swing; and (4) an inability to assess the potential benefit of rectus femoris procedure and hamstring preservation.

Conclusions

Overall, the combination of patellar-lowering surgery with multilevel surgery demonstrated superior improvements in stance-phase knee kinematics compared with multilevel surgery alone, despite an increase in anterior pelvic tilt and a longer-term knee flexion reduction during the swing phase.

Level of evidence

Level III, Systematic review of level III studies.

Tibial intraneural ganglion cysts arising from the tibiofemoral joint: illustrative cases

BACKGROUND

Intraneural cysts involving the tibial nerve in the knee region (popliteal fossa) are rare. According to the articular (synovial) theory, which posits a joint origin for this pathology, these cysts originate from either the superior tibiofibular joint (STFJ) or the tibiofemoral (knee) joint. As tibial intraneural cysts arising from the tibiofemoral joint remain poorly understood, the authors present 2 illustrative cases and a review of the world's literature on all tibial intraneural ganglion cysts in the knee region.

OBSERVATIONS

Fourteen cases of tibial intraneural ganglion cysts arising from the tibiofemoral joint were identified in the literature. Different articular branch patterns were demonstrated, which could be explained by the varied, rich articular branch innervation at the knee. Favorable outcomes were observed in cases in which the articular branch had been disconnected and the cyst drained and were comparable to the outcomes seen in tibial intraneural ganglion cysts with an STFJ origin.

LESSONS

Tibial intraneural cysts in the knee region can be subdivided by their joint of origin: the STFJ or the tibiofemoral joint. Those arising from the tibiofemoral joint originate from different areas of the joint and propagate in predictable patterns, with favorable outcomes following surgical intervention when the joint connection is identified and treated. The origin of tibial intraneural cysts from the tibiofemoral joint are more complex than those originating from the STFJ but seem to have similar propagation patterns and outcomes.

Effect of surface matching mismatch of focal knee articular prosthetic on tibiofemoral contact stress using finite element analysis

Aims

Focal knee arthroplasty is an attractive alternative to knee arthroplasty for young patients because it allows preservation of a large amount of bone for potential revisions. However, the mechanical behaviour of cartilage has not yet been investigated because it is challenging to evaluate in vivo contact areas, pressure, and deformations from metal implants. Therefore, this study aimed to determine the contact pressure in the tibiofemoral joint with a focal knee arthroplasty using a finite element model.

Methods

The mechanical behaviour of the cartilage surrounding a metal implant was evaluated using finite element analysis. We modelled focal knee arthroplasty with placement flush, 0.5 mm deep, or protruding 0.5 mm with regard to the level of the surrounding cartilage. We compared contact stress and pressure for bone, implant, and cartilage under static loading conditions.

Results

Contact stress on medial and lateral femoral and tibial cartilages increased and decreased, respectively, the most and the least in the protruding model compared to the intact model. The deep model exhibited the closest tibiofemoral contact stress to the intact model. In addition, the deep model demonstrated load sharing between the bone and the implant, while the protruding and flush model showed stress shielding. The data revealed that resurfacing with a focal knee arthroplasty does not cause increased contact pressure with deep implantation. However, protruding implantation leads to increased contact pressure, decreased bone stress, and biomechanical disadvantage in an in vivo application.

Conclusion

These results show that it is preferable to leave an edge slightly deep rather than flush and protruding.

Ambulatory support moment contribution patterns and MRI-detected tibiofemoral and patellofemoral disease worsening in adults with knee osteoarthritis: A preliminary study

We investigated whether baseline sagittal-plane ankle, knee, and hip contribution to the total support moment (TSM) are each associated with baseline-to-2-year tibiofemoral and patellofemoral tissue damage worsening in adults with knee osteoarthritis. Ambulatory lower-limb kinetics were captured and computed. TSM is the sum of ankle, knee, and hip extensor moments at each instant during gait. Ankle, knee, and hip contributions to TSM were computed as joint moments divided by TSM, expressed as percentages. Participants underwent MRI of both knees at baseline and 2 years later. Logistic regression models assessed associations of baseline ankle contribution to TSM with baseline-to-2-year cartilage damage and bone marrow lesion worsening, adjusted for age, sex, BMI, gait speed, disease severity, and pain. We used similar analytic approaches for knee and hip contributions to TSM. Sample included 391 knees from 204 persons (age[SD]: 64[10] years; 76.5% women). Greater ankle contribution may be associated with increased odds of tibiofemoral cartilage damage worsening (OR = 2.38; 95% CI: 1.02-5.57) and decreased odds of patellofemoral bone marrow lesion worsening (OR = 0.14; 95% CI: 0.03-0.73). The ORs for greater knee contribution were in the protective range for tibiofemoral compartment and in the deleterious range for patellofemoral. Greater hip contribution may be associated with increased odds of tibiofemoral worsening (OR = 2.71; 95% CI: 1.17-6.30). Greater ankle contribution to TSM may be associated with baseline-to-2-year tibiofemoral worsening, but patellofemoral tissue preservation. Conversely, greater knee contribution may be associated with patellofemoral worsening, but tibiofemoral preservation. Preliminary findings illustrate potential challenges in developing biomechanical interventions beneficial to both tibiofemoral and patellofemoral compartments.

A Novel Kinematic Model of the Tibiofemoral Joint Based on a Parallel Mechanism

This paper presents a complete kinematic model of the tibiofemoral joint (TFJ) based on a RRPP + 4-SPS parallel mechanism, where R, P, and S stand for revolute, prismatic, and spherical joints, respectively. The model accounts for the contact between tibia and femur, and the four major ligaments: anterior cruciate, posterior cruciate, medial collateral, and lateral collateral, with anatomical significance in their length variations. An experimental flexion passive motion task is performed, and the kinematic model is tested to determine its capability to reproduce the workspace of the motion task. In addition, an optimization process is performed to simulate prescribed ligament length variations during the motion task. The proposed kinematic model is capable to reproduce with high accuracy an experimental three-dimensional workspace, and at the same time, to simulate prescribed ligament length variation during the spatial flexion task. Prescribed ligament length variations are achieved through an optimization process of the ligament insertion points. This model can be used to improve the multibody kinematic optimization (MKO) process during gait analysis, and also in the design of rehabilitation devices as well as trajectories to accelerate the recovery of injured ligaments. The model shows potential to predict ligament length variations during different motion tasks, and can serve as a basis to develop complex models for kinetostatic and dynamic analyses without dealing with computationally expensive models.

Relationship Between 3 Single-Leg Functional Performance Tests for Netball Noncontact Knee Injury Prevention Screening in Uninjured Female Adult Players

CONTEXT

Single- versus double-leg landing events occur the majority of the time in a netball match. Landings are involved in large proportions of netball noncontact knee injury events. Of all landing-induced anterior cruciate ligament injuries, most occur during single-leg landings. Knowledge of whether different single-leg functional performance tests capture the same or different aspects of lower-limb motor performance will therefore inform clinicians' reasoning processes and assist in netball noncontact knee injury prevention screening.

OBJECTIVE

To determine the correlation between the triple hop for distance (THD), single hop for distance (SHD), and vertical hop (VH) for the right and left lower limbs in adult female netball players.

DESIGN

Cross-sectional.

SETTING

Local community netball club.

PARTICIPANTS

A total of 23 players (age 28.7 [6.2] y; height 171.6 [7.0] cm; mass 68.2 [9.8] kg).

INTERVENTIONS

There were 3 measured trials (right and left) for THD, SHD, and VH, respectively.

MAIN OUTCOME MEASURES

Mean hop distance (percentage of leg length [%LL]), Pearson intertest correlation (r), and coefficient of determination (r2).

RESULTS

Values (right and left; mean [SD]) were as follows: THD, 508.5 (71.8) %LL and 510.9 (56.7) %LL; SHD, 183.4 (24.6) %LL and 183.0 (21.5) %LL; and VH, 21.3 (5.2) %LL and 20.6 (5.0) %LL. All correlations were significant (P ≤ .05), r/r2 values (right and left) were THD-SHD, .91/.83 and .87/.76; THD-VH, .59/.35 and .51/.26; and SHD-VH, .50/.25 and .37/.17. A very large proportion of variance (76%-83%) was shared between the THD and SHD. A small proportion of variance was shared between the THD and VH (25%-35%) and SHD and VH (17%-25%).

CONCLUSION

The THD and SHD capture highly similar aspects of lower-limb motor performance. In contrast, the VH captures aspects of lower-limb motor performance different to the THD or SHD. Either the THD or the SHD can be chosen for use within netball knee injury prevention screening protocols according to which is reasoned as most appropriate at a specific point in time. The VH, however, should be employed consistently alongside rather than in place of the THD or SHD.

In vivo tibiofemoral cartilage strain mapping under static mechanical loading using continuous GRASP-MRI

BACKGROUND

Quantification of dynamic biomechanical strain in articular cartilage in vivo; in situ using noninvasive MRI techniques is desirable and may potentially be used to assess joint pathology.

PURPOSE

To demonstrate the use of static mechanical loading and continuous 3D-MRI acquisition of the human knee joint in vivo to measure the strain in the tibiofemoral articular cartilage.

STUDY TYPE

Prospective.

SUBJECTS

Five healthy human volunteers (four women, one man; age 25.6 ± 1.7) underwent MRI at rest, under static mechanical loading condition, and during recovery.

FIELD STRENGTH/SEQUENCE

A field strength of 3T was used. The sequence used was 3D-continuous golden angle radial sparse parallel (GRASP) MRI and compressed sensing (CS) reconstruction.

ASSESSMENT

Tibiofemoral cartilage deformation maps under loading and during recovery were calculated using an optical flow algorithm. The corresponding Lagrangian strain was calculated in the articular cartilage.

STATISTICAL TESTS

Range of displacement and strain in each subject, and the resulting mean and standard deviation, were calculated.

RESULTS

During the loading condition, the cartilage displacement in the direction of loading ranged from a minimum of -673.6 ± 121.9 μm to a maximum of 726.5 ± 169.5 μm. Corresponding strain ranged from a minimum of -7.0 ± 4.2% to a maximum of 5.4 ± 1.6%. During the recovery condition, the cartilage displacement in the same direction reduced to a minimum of -613.0 ± 129.5 μm and a maximum of 555.7 ± 311.4 μm. The corresponding strain range reduced to a minimum of -1.6 ± 7.5% to a maximum of 4.2 ± 2.6%.

DATA CONCLUSION

This study shows the feasibility of using static mechanical loading with continuous GRASP-MRI acquisition to measure the strain in the articular cartilage. By measuring strain during the loading and recovery phases, dynamic strain information in the articular cartilage might be able to be investigated.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2020;51:426-434.

Alignment differs between patellofemoral osteoarthritis cases and matched controls: An upright 3D MRI study

Patellofemoral (PF) osteoarthritis (OA) is a prevalent and clinically important knee OA subgroup. Malalignment may be an important risk factor for PF OA. However, little is known about alignment in PF OA, particularly in an upright, weightbearing environment. Using a vertically-oriented open-bore MR scanner, we evaluated 3D knee alignment in 15 PF OA cases and 15 individually matched asymptomatic controls. We imaged one knee per participant while they stood two-legged at four flexion angles (0°, 15°, 30°, 45°), and also while they stood one-legged at 30° knee flexion. We calculated 3D patellofemoral and tibiofemoral alignment. Using mixed effects models, four of the five patellofemoral measures differed by group. For key measures, PF OA patellae were 6.6° [95%CI 5.0, 8.2] more laterally tilted, 2.4 mm [1.3, 3.5] more laterally translated, and at least 3.7 mm [0.2, 7.2] more proximally translated compared to controls (more with knees flexed). Alignment did not differ between two-legged stance and one-legged stance in either group. Statement of Clinical Significance: Our study demonstrated significant and clinically relevant differences in alignment between PF OA cases and controls in upright standing and squatting positions. Our findings were similar to those in previous studies of PF OA using traditional MR scanners in supine positions, supporting the clinical usefulness of existing methods aimed at identifying individuals who may benefit from interventions designed to correct malalignment. © 2019 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of the Orthopaedic Research Society. 9999:1-9, 2019.

Effect of Lower Limb Alignment in Medial Meniscus-Deficient Knees on Tibiofemoral Contact Pressure

Background:

Degenerative medial meniscal tears and subsequent partial meniscal resection compromise meniscal function and lead to an overload of the medial compartment. In addition, lower limb alignment plays a key role in load distribution between the medial and lateral knee compartments, and varus alignment is a potential risk factor for medial osteoarthritis.

Purpose/Hypothesis:

The purpose of this biomechanical study was to investigate the effect of valgus and varus alignment on peak pressure and contact area in knees with concomitant horizontal medial meniscal tears and subsequent leaflet resection. It was hypothesized that varus alignment in combination with meniscal loss leads to the highest peak pressure within the medial compartment.

Study Design:

Controlled laboratory study.

Methods:

Six fresh-frozen human cadaveric knees were axially loaded using a 1000-N compressive load in full extension with the mechanical axis rotated to intersect the tibial plateau at 40%, 45%, 50%, 55%, and 60% of its width (TPW) to simulate varus and valgus alignment. Tibiofemoral peak contact pressure and contact area of the medial and lateral compartments were determined using pressure-sensitive foils in each of 4 different meniscal conditions: intact, 15-mm horizontal tear of the posterior horn, inferior leaflet resection, and resection of both leaflets.

Results:

The effect of alignment on peak pressure (normalized to the neutral axis) within the medial compartment in cases of an intact meniscus was measured as follows: varus shift resulted in a mean increase in peak pressure of 18.5% at 45% of the TPW and 37.4% at 40% of the TPW, whereas valgus shift led to a mean decrease in peak pressure of 8.7% at 55% of the TPW and 23.1% at 60% of the TPW. Peak pressure changes between the intact meniscus and resection within the medial compartment was less in valgus-aligned knees (0.21 MPa at 60% TPW, 0.59 MPa at 50% TPW, and 0.76 MPa at 40% TPW). Contact area was significantly reduced after partial meniscal resection in the neutral axis (intact, 553.5 ± 87.6 mm²; resection of both leaflets, 323.3 ± 84.2 mm²; P < .001). This finding was consistent in any alignment.

Conclusion:

Both partial medial meniscal resection and varus alignment led to an increase in medial compartment peak pressure. Valgus alignment prevented medial overloading by decreasing contact pressure even after partial meniscal resection. A horizontal meniscal tear did not influence peak pressure and contact area even in varus alignment.

Clinical Relevance:

As a clinical consequence, partial meniscal resection should be avoided to maintain the original biomechanical behavior, and the mechanical axis should be taken into account if partial meniscectomy is necessary.

Statistical shape model-based prediction of tibiofemoral cartilage

Computed tomography is used more routinely to design patient-specific instrumentation for knee replacement surgery. Its moderate imaging cost and simplified segmentation reduce design costs compared with magnetic resonance (MR) imaging, but it cannot provide the necessary cartilage information. Our method based on statistical shape modelling proved to be successful in predicting tibiofemoral cartilage in leave-one-out experiments. The obtained accuracy of 0.54 mm for femur and 0.49 mm for tibia outperforms the average cartilage thickness distribution and reported inter-observer MR segmentation variability. These results suggest that shape modelling is able to predict tibiofemoral cartilage with sufficient accuracy to design patient-specific instrumentation.

Reliability and Minimal Detectable Change Values for Predictions of Knee Forces during Gait and Stair Ascent Derived from the FreeBody Musculoskeletal Model of the Lower Limb

FreeBody is a musculoskeletal model of the lower limb used to calculate predictions of muscle and joint contact forces. The validation of FreeBody has been described in a number of publications; however, its reliability has yet to be established. The purpose of this study was, therefore, to establish the test-retest reliability of FreeBody in a population of healthy adults in order to add support to previous and future research using FreeBody that demonstrates differences between cohorts after an intervention. We hypothesized that test-retest estimations of knee contact forces from FreeBody would demonstrate a high intra-class correlation. Kinematic and kinetic data from nine older participants (4 men: mean age = 63 ± 11 years; 5 women: mean age = 49 ± 4 years) performing level walking and stair ascent was collected on consecutive days and then analyzed using FreeBody. There was a good level of intra-session agreement between the waveforms for the individual trials of each activity during testing session 1 (R = 0.79-0.97). Similarly, overall there was a good inter-session agreement within subjects (R = 0.69-0.97) although some subjects showed better agreement than others. There was a high level of agreement between the group mean waveforms of the two sessions for all variables (R = 0.882-0.997). The intra-class correlation coefficients (ICC) were very high for peak tibiofemoral joint contact forces (TFJ) and hamstring forces during gait, for peak patellofemoral joint contact forces and quadriceps forces during stair ascent and for peak lateral TFJ and the proportion of TFJ accounted for by the medial compartment during both tasks (ICC = 0.86-0.96). Minimal detectable change (MDC) of the peak knee forces during gait ranged between 0.43 and 1.53 × body weight (18-170% of the mean peak values). The smallest MDCs were found for medial TFJ share (4.1 and 5.8% for walking and stair ascent, respectively, or 4.8 and 6.7% of the mean peak values). In conclusion, the results of this study support the use of FreeBody to investigate the effect of interventions on muscle and joint contact forces at the cohort level, but care should be taken if using FreeBody at the subject level.

INVESTIGATING THE EFFECTIVENESS OF KINESIO® TAPING SPACE CORRECTION METHOD IN HEALTHY ADULTS ON PATELLOFEMORAL JOINT AND SUBCUTANEOUS SPACE

BACKGROUND

Limited quantitative, physiological evidence exists regarding the effectiveness of Kinesio® Taping methods, particularly with respect to the potential ability to impact underlying physiological joint space and structures. To better understand the impact of these techniques, the underlying physiological processes must be investigated in addition to the examination of more subjective measures related to pain in unhealthy tissues.

HYPOTHESIS/PURPOSE

The purpose of this study was to determine whether the Kinesio® Taping Space Correction Method created a significant difference in patellofemoral joint space, as quantified by diagnostic ultrasound.

STUDY DESIGN

Pre-test/post-test prospective cohort study.

METHODS

Thirty-two participants with bilaterally healthy knees and no past history of surgery took part in the study. For each participant, diagnostic ultrasound was utilized to collect three measurements: the patellofemoral joint space, the distance from the skin to the superficial patella, and distance from the skin to the patellar tendon. The Kinesio® Taping Space Correction Method was then applied. After a ten-minute waiting period in a non-weight bearing position, all three measurements were repeated. Each participant served as his or her own control.

RESULTS

Paired t tests showed a statistically significant difference (mean difference = 1.1 mm, t_[3,1] = 2.823, p = 0.008, g = .465) between baseline and taped conditions in the space between the posterior surface of the patella to the medial femoral condyle. Neither the distance from the skin to the superficial patella nor the distance from the skin to the patellar tendon increased to a statistically significant degree.

CONCLUSIONS

The application of the Kinesio® Taping Space Correction Method increases the patellofemoral joint space in healthy adults by increasing the distance between the patella and the medial femoral condyle, though it does not increase the distance from the skin to the superficial patella nor to the patellar tendon.

LEVEL OF EVIDENCE

3.

Atlas-based automatic measurements of the morphology of the tibiofemoral joint

PURPOSE

Anatomical metrics of the tibiofemoral joint support assessment of joint stability and surgical planning. We propose an automated, atlas-based algorithm to streamline the measurements in 3D images of the joint and reduce user-dependence of the metrics arising from manual identification of the anatomical landmarks.

METHODS

The method is initialized with coarse registrations of a set of atlas images to the fixed input image. The initial registrations are then refined separately for the tibia and femur and the best matching atlas is selected. Finally, the anatomical landmarks of the best matching atlas are transformed onto the input image by deforming a surface model of the atlas to fit the shape of the tibial plateau in the input image (a mesh-to-volume registration). We apply the method to weight-bearing volumetric images of the knee obtained from 23 subjects using an extremity cone-beam CT system. Results of the automated algorithm were compared to an expert radiologist for measurements of Static Alignment (SA), Medial Tibial Slope (MTS) and Lateral Tibial Slope (LTS).

RESULTS

Intra-reader variability as high as ~10% for LTS and 7% for MTS (ratio of standard deviation to the mean in repeated measurements) was found for expert radiologist, illustrating the potential benefits of an automated approach in improving the precision of the metrics. The proposed method achieved excellent registration of the atlas mesh to the input volumes. The resulting automated measurements yielded high correlations with expert radiologist, as indicated by correlation coefficients of 0.72 for MTS, 0.8 for LTS, and 0.89 for SA.

CONCLUSIONS

The automated method for measurement of anatomical metrics of the tibiofemoral joint achieves high correlation with expert radiologist without the need for time consuming and error prone manual selection of landmarks.

Open Knee: Open Source Modeling and Simulation in Knee Biomechanics

Virtual representations of the knee joint can provide clinicians, scientists, and engineers the tools to explore mechanical functions of the knee and its tissue structures in health and disease. Modeling and simulation approaches such as finite element analysis also provide the possibility to understand the influence of surgical procedures and implants on joint stresses and tissue deformations. A large number of knee joint models are described in the biomechanics literature. However, freely accessible, customizable, and easy-to-use models are scarce. Availability of such models can accelerate clinical translation of simulations, where labor-intensive reproduction of model development steps can be avoided. Interested parties can immediately utilize readily available models for scientific discovery and clinical care. Motivated by this gap, this study aims to describe an open source and freely available finite element representation of the tibiofemoral joint, namely Open Knee, which includes the detailed anatomical representation of the joint's major tissue structures and their nonlinear mechanical properties and interactions. Three use cases illustrate customization potential of the model, its predictive capacity, and its scientific and clinical utility: prediction of joint movements during passive flexion, examining the role of meniscectomy on contact mechanics and joint movements, and understanding anterior cruciate ligament mechanics. A summary of scientific and clinically directed studies conducted by other investigators are also provided. The utilization of this open source model by groups other than its developers emphasizes the premise of model sharing as an accelerator of simulation-based medicine. Finally, the imminent need to develop next-generation knee models is noted. These are anticipated to incorporate individualized anatomy and tissue properties supported by specimen-specific joint mechanics data for evaluation, all acquired in vitro from varying age groups and pathological states.

Management strategies for osteochondritis dissecans of the knee in the skeletally immature athlete

SYNOPSIS

Osteochondritis dissecans (OCD) is a disorder resulting in focal breakdown of the subchondral bone, with potential disruption of the overlying articular cartilage. The femoral condyles of the knee are the most common locations for OCD, and the incidence of OCD appears to be increasing among active children. Juvenile OCD (JOCD) can be distinguished from adult OCD by the presence of open growth plates. Due to a lack of evidence on its early diagnosis, optimal treatment, and long-term course of healing, JOCD presents a unique challenge for the health care team. Approximately 50% to 67% of stable JOCD lesions heal successfully with nonoperative treatment. For unstable lesions and stable lesions that fail nonoperative treatment, a variety of surgical interventions can be utilized to stimulate bony healing and address articular cartilage lesions. It is recommended that rehabilitation of JOCD be tailored to the individual patient, based on the stage and radiographic status of the lesion and the mode of surgery employed when surgically addressed. Although there is a growing body of literature on this condition, the etiology and optimal methods for treatment, rehabilitation, and evaluating outcomes remain inconclusive due to a lack of quality evidence.

LEVEL OF EVIDENCE

Therapy, level 5.

The effect of the material property change of anterior cruciate ligament by ageing on joint kinematics and biomechanics under tibial varus/valgus torques

It is known that the anterior cruciate ligament (ACL) plays a role in providing joint stabilities under tibial varus/valgus torques and the material behavior of the ACL has changed with ageing. However, the effect of this variation of the ACL material property on joint kinematics and biomechanics under tibial varus/valgus torques has still not been clarified.In this paper, three finite element (FE) models of an intact tibiofemoral joint were reconstructed with different ACL material properties, corresponding to the ACL on the younger, middle and older ages, respectively. The joint kinematics, the stress distribution and resultant force of the ACL were obtained under a tibial varus or valgus torque load. It was found that the variation in the ACL material property would result in great changes in some joint displacements (i.e., the tibial anterior translation and external rotation). The maximal stress value in the ACL had also altered while the stress distribution did not varied obviously. The great change in the tibial anterior translation illustrated that ACL played an important role against varus/valgus torques by controlling the coupled tibial anterior translation//external rotation rather than the corresponding varus/valgus rotation.

Reconstructing the knee joint mechanism from kinematic data

The interpretation of joint kinematics data in terms of displacements is a product of the type of movement, the measurement technique and the underlying model of the joint implemented in optimization procedures. Kinematic constraints reducing the number of degrees of freedom (DOFs) are expected to compensate for measurement errors and noise, thus, increasing the reproducibility of joint angles. One approach already successfully applied by several groups approximates the healthy human knee joint as a compound hinge joint with minimal varus/valgus rotation. Most of these optimizations involve an orthogonality constraint. This contribution compares the effect of a model with and without orthogonality constraint on the obtained joint rotation angles. For this purpose, knee joint motion is simulated to generate kinematic data without noise and with normally distributed noise of varying size. For small noise the unconstrained model provides more accurate results, whereas for larger noise this is the case for the constrained model. This can be attributed to the shape of the objective function of the unconstrained model near its minimum.

Differences in radiographic features of knee osteoarthritis in African-Americans and Caucasians: the Johnston county osteoarthritis project

OBJECTIVE

To examine racial differences in tibiofemoral joint (TFJ) and patellofemoral joint (PFJ) radiographic osteoarthritis in African-American (AA) and Caucasian men and women.

METHOD

Multiple logistic regression was used to evaluate cross-sectional associations between race and tibiofemoral osteoarthritis (TF-OA) and the presence, severity and location of individual radiographic features of tibiofemoral joint osteoarthritis [TFJ-OA] (osteophytes, joint space narrowing [JSN], sclerosis and cysts) and patellofemoral joint osteoarthritis (PFJ-OA) (osteophytes, JSN and sclerosis), using data from the Johnston County Osteoarthritis Project. Proportional odds ratios (POR) assessed severity of TF-OA, TFJ and PFJ osteophytes, and JSN, adjusting for confounders. Generalized estimating equations accounted for auto-correlation of knees.

RESULTS

Among 3187 participants (32.5% AAs; 62% women; mean age 62 years), 6300 TFJ and 1957 PFJ were included. Compared to Caucasians, AA men were more likely to have TF-OA (adjusted odds ratio [aOR]=1.36; 95% CI, 1.00-1.86); tri-compartmental TFJ and PFJ osteophytes (aOR=3.06; 95%CI=1.96-4.78), and TFJ and PFJ sclerosis. AA women were more likely than Caucasian to have medial TFJ and tri-compartmental osteophytes (aOR=2.13; 1.55-2.94), and lateral TFJ sclerosis. AAs had more severe TF-OA than Caucasians (adjusted cumulative odds ratio [aPOR]=2.08; 95% CI, 1.19-3.64 for men; aPOR=1.56; 95% CI, 1.06-2.29 for women) and were more likely to have lateral TFJ JSN.

CONCLUSIONS

Compared to Caucasians, AAs were more likely to have more severe TF-OA; tri-compartmental disease; and lateral JSN. Further research to clarify the discrepancy between radiographic features in OA among races appears warranted.

Sex differences in coupled knee motions during the transition from non-weight bearing to weight bearing

Knee ligament injuries frequently happen when the joint transitions from non-weight bearing (NWB) to weight bearing (WB). To gain insight into the mechanism that produces these injuries, physically active females (N = 41) and males (N = 39) underwent measurement of coupled tibiofemoral joint displacements [anterior tibial translation (ATT) and varus-valgus and internal-external rotations] and neuromuscular responses as the knee transitioned from NWB to WB in response to a 40% body weight load applied under the control of gravity. The transition from NWB to WB produced no difference in ATT between males and females; however, significant sex-based differences were noted for both transverse and frontal plane knee motions. With the knee NWB, females were in a greater absolute valgus compared to males (6.6 vs. 5.0 degrees), and moved through greater varus motion than males during the transition from NW to WB (2.3 vs. 1.4 degrees), resulting in similar valgus alignment for both sexes at peak WB (4.3 vs. 3.6 degrees). In the transverse plane, the knees of females were positioned in more external rotation compared to males when NWB (1.4 vs. -0.3 degrees), then females externally rotated their knees while males internally rotated their knees during the transition from NWB to WB. This resulted in a 3.4 degrees difference in transverse plane knee position at peak WB (2.3 vs. -1.1 degrees). Our findings suggest that the coupled knee motions produced during the transition from NWB to WB are sex dependent, and may provide insight into the knee motion patterns that place females at increased risk of knee ligament injury.

Effects of a contoured articular prosthetic device on tibiofemoral peak contact pressure: a biomechanical study

Many middle-aged patients are affected by localized cartilage defects that are neither appropriate for primary, nor repeat biological repair methods, nor for conventional arthroplasty. This in vitro study aims to determine the peak contact pressure in the tibiofemoral joint with a partial femoral resurfacing device (HemiCAP, Arthrosurface Inc., Franklin, MA, USA). Peak contact pressure was determined in eight fresh-frozen cadaveric specimens using a Tekscan sensor placed in the medial compartment above the menisci. A closed loop robotic knee simulator was used to test each knee in static stance positions (5 degrees /15 degrees /30 degrees /45 degrees ) with body weight ground reaction force (GRF), 30 degrees flexion with twice the body weight (2tBW) GRF and dynamic knee-bending cycles with body weight GRF. The ground reaction force was adjusted to the living body weight of the cadaver donor and maintained throughout all cycles. Each specimen was tested under four different conditions: Untreated, flush HemiCAP implantation, 1-mm proud implantation and 20-mm defect. A paired sampled t test to compare means (significance, P < or = 0.05) was used for statistical analysis. On average, no statistically significant differences were found in any testing condition comparing the normal knee with flush device implantation. With the 1-mm proud implant, statistically significant increase of peak contact pressures of 217% (5 degrees stance), 99% (dynamic knee bending) and 90% (30 degrees stance with 2tBW) compared to the untreated condition was seen. No significant increase of peak contact pressure was evaluated with the 20-mm defect. The data suggests that resurfacing with the HemiCAP does not lead to increased peak contact pressure with flush implantation. However, elevated implantation results in increased peak contact pressure and might be biomechanically disadvantageous in an in vivo application.

A review of knee dislocations

OBJECTIVE

To inform health care professionals about the various mechanisms of this little-known injury, as well as its potentially limb-threatening complications. In addition, keys to immediate recognition and the importance of a thorough rehabilitation program are stressed.

DATA SOURCES

I searched MEDLINE (1966-2000) using the key words knee dislocation, knee injury, and tibiofemoral dislocation.

DATA SYNTHESIS

Knee dislocations are uncommon but very serious injuries. Because the joint may spontaneously reduce before the examiner reaches the patient, the examiner must be aware of the potential complications and rule out any neurovascular damage immediately.

CONCLUSIONS/RECOMMENDATIONS

Prompt recognition of this injury and proper care combined with an extensive rehabilitation program can greatly improve the prognosis for the patient. Neurovascular integrity should be assessed routinely for several days after the injury to ensure that complications do not develop.