Self-reported knee instability before and after total knee replacement surgery

<b>Objective</b>\ud \ud To determine the prevalence and burden of pain and activity limitations associated with retaining presurgery self-reported knee instability 6 months after <i>total knee replacement</i> (TKR) surgery and to identify early potentially modifiable risk factors for retaining knee instability in the operated knee after TKR surgery.\ud \ud <b>Methods</b>\ud \ud A secondary analysis was performed using measures obtained from 390 participants undergoing primary unilateral TKR and participating in a randomized clinical trial. Self-reported knee instability was measured using 2 items from the Activities of Daily Living Scale of the Knee Outcome Survey. Outcome measures were knee pain (range 0–20) and physical function (range 0–68) on the <i>Western Ontario and McMaster Universities Arthritis Index</i> (WOMAC), stair-climb power, 50-foot walk time, knee range of motion, and isometric knee flexion and extension strength.\ud \ud <b>Results</b>\ud \ud In this study, 72% of participants reported knee instability just prior to surgery, with 32% retaining instability in the operated knee 6 months after surgery. Participants retaining operated knee instability had significantly more knee pain and activity limitations 6 months after surgery, with mean ± SD WOMAC scores of 4.8 ± 3.7 and 17.5 ± 11.1, respectively, compared to participants without knee instability, with 2.9 ± 3.1 and 9.8 ± 9.2. The multivariable predictor model for retained knee instability included a high comorbidity score (>6), low stair-climb power (<150 watts), more pain in the operated knee (>7 of 20), and younger age (<60 years).\ud \ud <b>Conclusion</b>\ud \ud Self-reported knee instability is highly prevalent before and after TKR surgery and is associated with a considerable burden of pain and activity limitation in the operated knee. Increasing lower extremity muscle power may reduce the risk of retaining knee instability after TKR surgery