Background and purpose: Manipulation under anesthesia (MUA) is considered to be effective in treating stiffness after total knee arthroplasty (TKA). However, not all patients achieve a satisfactory range of motion (ROM) after MUA. This retrospective study determined the outcome of MUA and identified the factors affecting it.
Patients and methods: The final sample consisted of 150 MUAs performed on 145 patients. The parameters of interest were ROM and Knee Society Score (KSS) or Oxford Knee Score (OKS). The associations of preoperative, perioperative, and postoperative risk factors with gain in flexion and flexion at post-MUA follow-up (an average of 2 months after MUA) were analyzed using multivariable regression model.
Results: The mean of 26° (95% CI 23-29) gain in flexion and the mean of 3° (CI 2-4) gain in extension were noticed at post-MUA follow-up when compared with the ROM preceding MUA. The mean post-MUA-FU flexion was 99° (CI 97-102) and the mean post-MUA-FU extension deficit was 4° (CI 2-5). KSS (121 vs. 129) and OKS (29 vs. 28) were similar before and after MUA. The early timing of MUA was associated with better gain in flexion -0.04 (CI -0.08 to -0.01), while we found no association between the timing of MUA and flexion after MUA -0.004 (CI -0.03 to 0.03). High BMI was associated with better gain in flexion 0.8 (CI 0.2-1.5).
Interpretation: We found that ROM improved substantially after MUA. The gain in flexion decreased as the time between TKA and MUA increased.