Summary

Lateral meniscus tears significantly impact in vivo knee kinematics, whereas for medial meniscus tears, no differences were observed in kinetics, and limited conflicting evidence for kinematics.

Abstract

Introduction/Objective:
Extensive ex vivo evidence on the role of the meniscus in load transmission and knee stability has paved the way for the current point of emphasis on preserving the menisci. In contrast to the robust body of work stemming from cadaveric studies, there is a relative paucity of in vivo biomechanics studies on the matter. The primary aim of this study is to systematically review the effect of meniscal tears on in vivo kinematics and kinetics.

Methods

Databases were queried for level I-IV studies reporting baseline data meeting the following criteria: in vivo studies of gait or motion analysis; cohorts with isolated meniscal pathology; available kinematics and/or kinetics outcome measures. Demographic data, method of motion analysis employed, tasks performed, and measured outcomes were extracted and qualitatively appraised. Risk of bias assessment was conducted using the MINORS index. Standardized mean differences with a random effects model were calculated by comparing meniscal tear cohorts and healthy controls whenever allowed by homogeneous outcomes.

Results

Thirteen studies were eligible, with a pooled sample of 176 medial meniscal and 74 lateral meniscal tears. Eleven studies assessed gait, while different tasks such as lunge, step-down, and squatting were assessed in one study each. There was considerable variability in the outcomes, as well as in the method of motion analysis. In terms of gait kinematics relative to healthy control, there is qualitative evidence of increased lateral tibial translation in medial meniscal root pathology, and reduction in the variability of articular motion in medial bucket-handle tears. Meta-analysis revealed statistically significant decreases in peak knee flexion angle during stance (p=.0001) and swing (p<.0001), as well as in the range of adduction-abduction (p<.0001) and internal-external rotation (p<.0001) for the pooled sample of lateral meniscus tears. In terms of kinetics relative to healthy control, while there was qualitative evidence for unloading of the injured knee (decreased peak support moment, knee flexion, and extension moments), meta-analysis failed to demonstrate significant differences for peak knee flexion (p = 0.11) and peak knee adduction moments (p = 0.45). The mean MINORS index score for risk of bias was 19.0, ranging from 15 to 22 (out of a maximum possible score of 24).

Conclusion

There is high heterogeneity in terms of reported outcomes from motion analysis studies assessing isolated meniscus tears and largely limited to gait analysis. Qualitative evidence suggests kinetics changes reflecting mechanisms for unloading the injured joint, and that prior ex vivo findings of impaired knee kinematics from meniscal pathology translate to the in vivo setting. There is statistical evidence of limited sagittal, coronal, and axial plane kinematics for lateral meniscus tears. Future research should include well-designed prospective studies assessing more demanding tasks.