Impact of flexion versus extension of knee position on outcomes after total knee arthroplasty: a meta-analysis.

INTRODUCTION: Controversy still exists regarding positioning of the knee in flexion or in extension after total knee arthroplasty (TKA) impacts treatment outcomes. In this meta-analysis, we evaluated if a postoperative knee position regime could positively affect the rehabilitation.

METHODS: A comprehensive search for randomized controlled trials (RCTs) assessing the effect of knee positioning after TKA was conducted. The outcomes of interest were blood loss and range of motion (ROM); total calculated blood loss (CBL), drainage volume, hidden blood loss (HBL), decline of hemoglobin level and requirement for blood transfusion.

RESULTS: Ten RCTs involving 962 knees were eligible for meta-analysis. Positioning the knee in flexion after TKA was significantly associated with lesser CBL (P < 0.00001), less HBL (P < 0.00001) and decreased requirement for blood transfusion (P = 0.06). On subgroup analyses, the flexion group was found to have significantly less decrease in hemoglobin level 48 h to 6 days after surgery (P = 0.003), while no significant difference was noted at 24 h after surgery (P = 0.29). Further,a superior ROM was observed in flexion group (5-7 days after surgery) (P = 0.002), while there was no significant difference at 6 weeks. No significant inter-group difference in wound drainage was observed at 24 h after surgery.

CONCLUSION: Positioning the knee in flexion in the early postoperative stage was associated with significantly lesser CBL, lesser HBL, decreased requirement for blood transfusion and better ROM at least in the early postoperative period, which may contribute to early rehabilitation. However, no significant difference was found in ROM at 6 weeks.