Is discharge knee range of motion a useful and relevant clinical indicator after total knee replacement? Part 1.

Objectives: Knee range of motion (ROM) at the point of discharge from acute care is used as a clinical indicator to benchmark performance between hospital services after total knee replacement (TKR). The utility of the current benchmark, including whether discharge ROM varies between hospitals, is unknown. This study aimed to determine whether the benchmark [≥80 degrees flexion and ≤5 degrees fixed flexion (extension)] is realistic and whether the service provider is a predictor of knee ROM.

Methods: A prospective, observational cohort study was conducted involving 176 TKR patients from four hospitals. Knee ROM was photographically assessed preoperatively and at discharge. 'Hospital', typical patient demographic data and preoperative ROM were identified a priori as potential predictors of knee ROM.

Results: Overall, 2% [95% CI (confidence interval) 1-6] of patients attained the ROM benchmark. Individual hospital attainment of the benchmark ranged 0-7% with a significant difference (P = 0.047) evident between the best performer and the remaining hospitals. The overall rates of attainment of the individual flexion (25%, 95% CI 19-32) and extension (15%, 95% CI 10-21) components were similarly low, although the scatter between hospitals was large [flexion (2-47%); extension (8-44%)]. Preoperative flexion and hospital were significant (P = 0.002) predictors of discharge flexion, explaining 21% of the variance. Similarly, hospital and preoperative extension together with gender were significant (P < 0.001) predictors of discharge extension, explaining 26% of the variance.

Conclusions: A small minority of patients attained the knee ROM benchmark, indicating the existing standard is unrealistic. Nevertheless, that 'hospital' is an important predictor confirms the potential of ROM for benchmarking purposes. Differences in physiotherapy practices may contribute to inter-hospital variation in discharge knee ROM together with other undefined factors. The causal relationships explaining the variation and the relationship between discharge ROM and longer-term outcome are avenues for future exploration which will help define the clinical relevance of the indicator.