Knee joint loading during gait in healthy controls and individuals with knee osteoarthritis.

OBJECTIVE: People with knee osteoarthritis (OA) are thought to walk with high loads at the knee which are yet to be quantified using modeling techniques that account for subject specific electromyography (EMG) patterns, kinematics and kinetics. The objective was to estimate medial and lateral loading for people with knee OA and controls using an approach that is sensitive to subject specific muscle activation patterns.
METHODS: Sixteen OA and 12 control (C) subjects walked while kinematic, kinetic and EMG data were collected. Muscle forces were calculated using an EMG-Driven model and loading was calculated by balancing the external moments with internal muscle and contact forces.
RESULTS: OA subjects walked slower and had greater laxity, static and dynamic varus alignment, less flexion and greater knee adduction moment (KAM). Loading [normalized to body weight (BW)] was no different between the groups but OA subjects had greater absolute medial load than controls and maintained a greater %total load on the medial compartment. These patterns were associated with body mass, sagittal and frontal plane moments, static alignment and close to significance for dynamic alignment. Lateral compartment unloading during mid-late stance was observed in 50% of OA subjects.
CONCLUSIONS: Loading for control subjects was similar to data from instrumented prostheses. Knee OA subjects had high medial contact loads in early stance and half of the OA cohort demonstrated lateral compartment lift-off. Results suggest that interventions aimed at reducing BW and dynamic malalignment might be effective in reducing medial compartment loading and establishing normal medio-lateral load sharing patterns.