Abstract
Focal cartilage defects (FCDs) found in medial and lateral compartments of the knee are accompanied with patient-reported pain and loss of joint function. There is a deficit of evidence to explain why they occur. We hypothesise that aberrant knee joint loading may be partially responsible for FCD pathology, therefore this study aims to use 3-dimensional motion capture (MoCap) analysis methods to investigate differences in gait biomechanics of subjects with symptomatic FCDs.
11 subjects with Outerbridge grade II FCDs of the tibiofemoral joint (5 medial compartment, 6 lateral compartment) and 10 non-pathological controls underwent level-gait MoCap analysis using an infra-red camera (Qualisys) and force-plate (Bertec) passive marker system. 6-degree of freedom models were generated and used to calculate spatio-temporal measures, and frontal and sagittal plane knee, hip and ankle rotation and moment waveforms (Visual 3D). Principle component analysis (PCA) was used to score subjects based on common waveform features, and PC scores were tested for differences using Mann-Whitney tests (SPSS).
No group differences were found in BMI, age or spatio-temporal measures. Medial-knee FCD subjects experienced higher (p=0.05) overall knee adduction moments (KAMs) compared to controls. Conversely, lateral-knee FCD subjects found lower (p=0.031) overall KAMs. Knee flexion and extension moments (KFMs/KEMs) were relatively reduced (p=0.013), but only in medial FCD subjects. This was accompanied by a significantly (p=0.019) higher knee flexion angle (KFA) during late-stance.
KAMs have been shown to be predictive of frontal plane joint contact forces, and therefore our results may be reflective of FCD subjects overloading their respective diseased knee condyles. The differences in knee sagittal plane knee moments (KFMs/KEMs) and angles (KFA) seen in medial FCD subjects are suggestive of gait adaptations to pain. Overall these results suggest treatments of FCDs should consider offloading the respective affected condyle for better surgical outcomes.
