Asymmetrical biomechanics in knee osteoarthritis: a review of contralateral risk from primary disease to post-arthroplasty progression.

Knee osteoarthritis (OA) demonstrates asymmetric joint degeneration (contrasting with symmetric inflammatory arthritis), driven by abnormal lower-limb biomechanics. Patients exhibit persistent inter-limb asymmetries in kinematics (reduced knee flexion/range of motion), kinetics (elevated knee adduction moment and increased contralateral loading), plantar pressure distribution, and muscle strength (15-30% quadriceps deficit), even with bilaterally matched disease severity. These asymmetries endure for months to years after total knee arthroplasty (TKA), manifesting as reduced weight-bearing on the operated limb and compensatory overloading of the contralateral limb. The high incidence of contralateral TKA (39% within 10 years) underscores the clinical importance of persistent biomechanical asymmetry as a prominent and modifiable contributor to OA progression in the opposite knee. Targeted rehabilitation strategies promoting inter-limb symmetry may mitigate disease advancement and improve functional outcomes.