Cryotherapy for postoperative pain relief following knee arthroplasty.

Ninety consecutive patients undergoing primary knee arthroplasty received local cryotherapy 72 hours after surgery for pain relief. Thermal-pad circulating temperatures were randomly assigned to 50 degrees, 60 degrees, or 70 degrees F (room temperature). Pain relief was monitored using patient-controlled analgesia machines. The amount of morphine received and number of attempts per hour were statistically analyzed with relation to temperature group, age, sex, weight, side, and diagnosis. The amount of morphine injected was positively correlated to the number of attempts per hour and moderately correlated to body weight. There was no correlation between thermal-pad temperature or any other parameter and the amount of morphine injected after surgery.