Knee Flexion Contracture Associated With a Contracture and Worse Function of the Contralateral Knee: Data From the Osteoarthritis Initiative

Objective: Patients at risk of developing knee osteoarthritis (OA) or those already diagnosed with knee OA may present with a knee flexion contracture (FC). A knee FC can cause pain and can decrease function. By altering lower extremity biomechanics, the effect of a knee FC goes beyond the affected joint. Compensatory movements during gait can chronically affect other joints in both lower limbs. Few studies describe the effect of a knee FC on, or direct assessment toward, the contralateral knee. We investigated the associations between knee FC with range of extension, function, pain, and stiffness of the contralateral knee.

Design: Cross-sectional, using the Osteoarthritis Initiative Database.

Participants: Outpatient cohort study, recruiting from 4 United States academic health care centers (N=4796). Two groups were included: those at risk of developing OA (n=3284 knees), and those already with radiographic OA (n=1390 knees).

Main outcomes measures: Maximum contralateral knee extension and Western Ontario and McMaster Osteoarthritis Index (WOMAC) scores. Statistical analysis included a mixed linear model evaluating for independent associations between the index knee FC and contralateral knee outcome measures.

Results: A knee FC was associated with a contralateral knee FC (P<.001) with contralateral FC severity dependent on severity of the index knee FC (P<.001). Participants at risk of developing OA with moderate FC showed worse function in the contralateral knee than those with mild FC (WOMAC functional subscale ± SD: 7.6±10.1 vs 5.5±8.8; P=.036). Mixed linear analysis confirmed an independent association between knee FC severity and contralateral WOMAC function.

Conclusions: Having an FC in 1 knee was associated with an FC in the contralateral knee for participants who were at risk of developing OA and for those with a current diagnosis of OA. For those at risk of developing OA, the severity of knee FC was an independent predictor for loss of contralateral knee function. Rehabilitation of patients with or at risk of developing OA should consider the restoration of extension and function for both knees.