INTER-LIMB STRENGTH SYMMETRY AND RISK OF TOTAL KNEE ARTHROPLASTY: A SURVIVAL ANALYSIS

The purpose of this study was to investigate the relationship of knee extension strength symmetry status (symmetrical versus asymmetrical) to the risk of undergoing total knee arthroplasty (TKA) among participants with or at risk for knee osteoarthritis in the Osteoarthritis Initiative (OAI). Participants were selected from the OAI, a multi-center, longitudinal, cohort, including 4796 individuals with or at risk for knee osteoarthritis. All participants had complete data for baseline bilateral knee extension strength (collected isometrically at 60deg from full extension) and TKA date, if applicable. Only the first TKA was used for participants with bilateral TKA dates. All strength values were normalized to body mass (N/kg). Strength symmetry-index values were calculated for knee extension using the formula ((XR-XL)/(0.5(XR+XL))*100). A ±10% threshold was set to indicate asymmetry between limbs. Participants were grouped based on knee extension strength symmetry. A SI of ≥ +10% indicated greater strength in their right limb, a SI between -9.9 to +9.9 was considered symmetric, and a SI of ≤ -10% indicated greater strength in their left limb. The relationship between knee extension strength symmetry status and TKA was examined using Kaplan-Meier curves to evaluate survival based on the Mantel-Cox log-rank test. Multivariable Cox regression models were adjusted for age, sex, BMI, baseline Kellgren-Lawrence (KL) grades and baseline pain to determine the multivariable-adjusted hazard ratios (aHRs) of TKA in symmetrical versus asymmetrical (SI = ≥ +10% and ≤ -10%) participants. Limb-specific aHRs were also calculated for risk of right and left TKA separately. In 3877 participants over 10-years, 373 first limb TKAs were performed (192 right limb and 181 left limb). Log-rank tests indicated that the distribution of TKAs across symmetry status was significantly different (p In conclusion, knee extension strength asymmetry may be an easily accessible and useful clinical measure to identify individuals at increased risk for progression to TKA. Interventions targeting not only muscle strength of the affected limb, but the symmetry between limbs, may improve clinical outcomes. Further work to understand the dynamics of asymmetry over time is needed.