(HealthDay News) — For patients undergoing primary total knee replacement, surgical, radiographic, and demographic variables associated with postoperative pain have been identified in two studies presented at the annual meeting of the American Academy of Orthopaedic Surgeons, held from March 11–15 in New Orleans.

Vasilios I. Sakellariou, MD, from the Hospital for Special Surgery in New York City, and colleagues investigated perioperative radiographic and surgical risk factors associated with postoperative pain in 273 patients who underwent primary total knee replacements. The researchers identified general anesthesia, tourniquet pressure, amount of blood loss, overhanging femoral implant, large patella size, and increased postoperative patellar congruence angle as risk factors for severe postoperative pain at rest. Large patella size, overstuffing of the patellofemoral joint, increased preoperative femoral offset, and femoral component alignment in excessive valgus were identified as predictors of pain with activity.

In a second study, Sakellariou and colleagues examined the correlation between demographic data and different levels of patient-reported postoperative pain among 273 patients who underwent primary total knee replacement. The researchers found that female gender; age group 45–55 or 56–65 years; posttraumatic, rheumatoid, and osteoarthritis; obesity; and higher reported pain at admission were risk factors for severe postoperative pain at rest. Predictors of pain with activity included age (45–55 and 56–65 years), obesity, and higher reported pain at admission.

“Many factors play a role, and our studies found that younger female patients, particularly those with posttraumatic or rheumatoid arthritis, had the highest pain scores,” a coauthor said in a statement.

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