• knee
• osteoarthritis
• biomechanics

Although osteoarthritis (OA) is a common cause of disability in people over 65 years,¹ the causes and pathogenesis of knee OA remain largely unknown. In addition to biological studies, there is increasing interest in the contribution of biomechanical variables in the pathogenesis and management of this disease.^2–6

OA of the knee occurs most commonly in the medial tibiofemoral compartment,³ and increased regional load across this compartment’s articular cartilage is believed to be an important factor in the pathogenesis of the disease.^2–6 The external knee adduction moment is argued to distribute 60–80% of total intrinsic knee compressive load to the medial tibiofemoral compartment,³ and people with medial tibiofemoral OA tend to walk with larger knee adduction moments than normal subjects, resulting in increased medial compartment pressure.^2,7 Despite this, there is no clear evidence to suggest whether biomechanical abnormalities such as increased knee adduction moments cause or occur as a result of OA because all previous studies have examined people with established disease.

The knee adduction moment is generated by the combination of the ground reaction force, which passes medial to the centre of the knee joint, and the perpendicular distance of this force from the centre of the joint.³ Given that varus alignment of the lower limb theoretically …