Drain Removal Before Versus After CPM in Primary Total Knee Arthroplasty

The aim of this prospective randomized controlled study was to determine whether the timing of drain removal in relation to continuous passive motion (CPM) application influences postoperative residual hematoma formation following primary total knee arthroplasty (TKA). Our primary hypothesis was that removing the drain after initiating CPM would result in less residual hematoma, as CPM-induced intra-articular fluid and blood mobilization would be evacuated through the drain before its removal, thereby reducing postoperative fluid accumulation.

This prospective, parallel-group interventional study was conducted at a single tertiary care center between June 2025 and December 2025 following approval by the institutional ethics committee. All patients provided written informed consent prior to participation. A total of 104 consecutive patients undergoing primary unilateral total knee arthroplasty (TKA) were enrolled during the study period. During follow-up, four patients from each group were lost, leaving 96 patients available for final analysis. Participants were allocated into two groups using a sequential alternating allocation method (2-1-2-1 sequence). Although not computer-generated, this prospective allocation approach ensured balanced group sizes throughout enrollment. Due to the nature of the intervention, allocation concealment and blinding were not applied. All surgical procedures were performed by senior arthroplasty surgeons using a standardized medial parapatellar approach under spinal anesthesia. A uniform perioperative protocol was applied to all patients, including antibiotic prophylaxis with intravenous cefazolin and thromboembolism prophylaxis with low-molecular-weight heparin. All procedures were performed under tourniquet control. A single standard intra-articular hemovac drain of identical size and model was placed in all patients prior to wound closure. Postoperatively, all patients underwent a standardized continuous passive motion (CPM) protocol approximately 24 hours after surgery. CPM was applied for 1 hour with a motion range of 0-90 degrees under supervision of the physiotherapy team. The only interventional difference between study groups was the timing of drain removal in relation to CPM therapy. In the first group, the hemovac drain was removed immediately before initiation of CPM. In the second group, the drain was removed immediately after completion of the CPM session. All other perioperative care and rehabilitation protocols were identical between groups.