Posterior capsular injections of ropivacaine during total knee arthroplasty: a randomized, double-blind, placebo-controlled study.

We investigated the hypothesis that a posterior capsular injection of ropivacaine would improve pain and accelerate functional recovery after total knee arthroplasty in a randomized, double-blind, placebo-controlled study design. Sixty-six patients received a standardized multimodal anesthesia protocol that included a femoral nerve block. Twenty milliliters of either saline (control) or ropivacaine (study group) was injected into the posterior capsule. Pain and function outcomes were recorded prospectively at 4, 8, 12, and 24 hours postinjection. Significantly more patients in the study group were able to perform a straight-leg raise at 8 and 12 hours. In addition, significantly more patients in the control group had a numeric pain score higher than 7/10 (severe pain) at the 12-hour evaluation. Other parameters of pain or functional recovery were not significantly different between the 2 groups. Posterior capsular injection did not improve the pain or accelerate the functional recovery after 12 hours in patients also receiving a femoral nerve block for pain control after total knee arthroplasty.