Predictors of outcome after manipulation under anaesthesia in patients with a stiff total knee arthroplasty.

PURPOSE: Flexion in a stiff total knee arthroplasty (TKA) can be improved by manipulation under anaesthesia (MUA). Although this intervention usually results in an improvement in range of motion, the expected result is not always achieved. The purpose of this study is to determine which factors affect range of motion after manipulation in patients with a stiff total knee.

METHODS: After exclusion (n = 22), the data of 158 patients (138 knees) with a stiff knee after TKA who received a manipulation under anaesthesia between 2004 and 2014 were retrospectively analysed. Pre-, peri- and post-operative variables were identified and examined for their influence on flexion after the manipulation using Kruskal-Wallis and Mann-Whitney U tests and Spearman correlations.

RESULTS: After MUA, a mean improvement in flexion of 30.3° was observed at the final follow-up. Preoperative TKA flexion, design of TKA and interval between TKA procedure and MUA were positive associated with an increase in flexion after MUA. MUA performed 12 weeks or more after TKA procedure deteriorated the outcome.

CONCLUSIONS: Three factors, pre-TKA flexion type of prosthesis and interval between TKA procedure and manipulation under anaesthesia, were found to have impact on flexion after TKA and MUA were identified. Results are expected to be inferior in patients with low flexion before TKA procedure or with a long interval (>12 weeks) between the TKA procedure and the manipulation under anaesthesia.

LEVEL OF EVIDENCE: IV.