Medial meniscus extrusion during gait identifies altered knee mechanical loading in early osteoarthritis of the knee.

PURPOSE: This study aimed to develop a modified knee adduction moment (KAM) measure as a composite measure of mechanical loading, incorporating medial meniscal extrusion (MME), and investigate whether it could distinguish patients with the biomechanical pathology of early knee osteoarthritis (OA) from healthy individuals. METHODS: This study included 23 patients with early knee OA (Kellgren-Lawrence grade 1-2), 14 healthy young (younger group) and 13 healthy elderly individuals (older group). In patients with knee OA, knee alignment was evaluated using hip-knee-ankle angle. For investigating the gait-related mechanical loading, the KAM, including the impulse value, was measured during walking using a motion analysis system synchronised with an ultrasound. MME waveforms were generated from continuous MME values obtained using ultrasound in video mode, and the difference between the minimum and maximum values of the MME behaviour was shown as the ΔMME. Furthermore, the modified KAM was calculated by multiplying the KAM impulse by the ΔMME value. RESULTS: No significant differences were observed in the KAM impulse among all groups. ΔMME and modified KAM were significantly higher in the knee OA group than in the younger and older groups. In the knee OA group, a significant correlation was observed only between the modified KAM and the hip-knee-ankle angle, whereas no significant correlation was found for the KAM or ΔMME alone. CONCLUSIONS: The modified KAM identified biomechanical features associated with mechanical loading stress in the medial compartment in patients with early-stage knee OA. LEVEL OF EVIDENCE: Level IV.