Effects of morphine on peri-articular infiltration analgesia in total knee arthroplasty: a prospective, double-blind, randomized controlled trial.

Adding morphine into the analgesic cocktail of PIA could reduce postoperative morphine consumption in TKA patients, but does not improve early pain relief or accelerate functional recovery or provide clinical benefits for TKA patients. In addition, the complications and safety of peri-articular morphine infiltration need to be further investigated in larger sample studies.