Predicting Functional Ability Following Total Knee Arthorplasty (TKA)

Abstract

PURPOSE: To identify pre- and post-operative predictors of post-TKA functional ability among knee OA patients that may aid in directing effective therapy prior to and following the TKA. METHODS: 63 Patients were consented and underwent testing and analysis. Functional ability was defined as the ability to complete four functional tasks, which included 6-minute walk distance, the number of sit-to-stand repetitions in 30-seconds, and the time to ascend and descend 22 stairs. Data was collected one week prior to and 4 weeks following their TKA. Other potential predictor variables collected included BMI, bilateral isokinetic knee extension and flexion strength, bilateral knee range of motion (ROM), WOMAC scales, and pain while performing each functional task. RESULTS: An analysis to identify significant correlations between the functional tasks and the potential predictor variables was performed. Significant correlates with each functional task were then entered into stepwise regression equations. Regression equations indicated that the pre-TKA 6-minute walk time and post-TKA surgical knee extension strength predicted 64% of the variance in the post-TKA 6-minute walk distance. Similarly, post-TKA sit-to-stand reps were significantly predicted (total R2 = .70) by pre-TKA sit-to-stand reps and post-TKA surgical knee extension strength. Post-TKA stair ascent was predicted by pre-TKA stair ascent, post-TKA surgical knee ROM, post-TKA knee extension strength and pre-TKA surgical knee flexion strength (total R2 = .63). Finally, post-TKA stair descent was predicted by pre-TKA stair descent, post-TKA knee extension strength, and pre-TKA surgical and non-surgical knee flexion strength (total R2 = .68). CONCLUSIONS: These findings indicate that the consistent predictors of postoperative functional ability among TKA patients are pre-operative functional ability and post-operative surgical knee extension strength. Previous investigators have reported these predictors are amenable through exercise interventions introduced prior to the TKA-"prehabilitation". Therefore, post-TKA functional ability may be facilitated by pre-operative exercise interventions.