Risk Factors for Post-Op Knee Pain

Knee replacement surgery recovery harder for women and the obese

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) One goal of knee replacement surgery for arthritis patients is to improve mobility and pain, but in many cases, pain after surgery presents a new issue for these patients.

Researchers behind two new studies wanted to explore postoperative pain in knee replacement patients and search for risk factors associated with pain after surgery.

These studies found that gender, age, weight and certain surgical factors were all associated with a greater risk for postoperative pain. Women, middle-aged adults and the obese were all more likely to have severe pain after a knee replacement.

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According to the authors of these new studies, which were led by Thomas P. Sculco, MD, of the Hospital for Special Surgery in New York City, persistent pain after knee replacement surgery is the main reason that patients report dissatisfaction after their operations.

These researchers explained that the rate of persistent postoperative pain after knee replacement surgery has been reported in anywhere from 5 to 44 percent of cases.

To explore the topic and potential risk factors for pain, Dr. Sculco and team reviewed electronic medical records to identify 273 patients who had a total knee replacement between October 2007 and March 2010.

These researchers reviewed the records to gather information on factors like age, gender, weight, type of arthritis and other medical issues. Pain was measured using the Visual Analog Scale for Pain (VAS), which records pain on a level from 0 to 10.

The first study focused on the patients' postoperative pain both when resting and when being active while the patients were still in the hospital recovering.

Dr. Sculco and team found that several factors were associated with a greater risk for severe postoperative pain, including gender, weight and arthritis type.

"Overall, the profile of the patient that is expected to have lower threshold of pain is the young, obese female with underlying post-traumatic or rheumatoid arthritis," the study's authors wrote.

The second study focused on surgical factors like the length of incision, duration of surgery and type of anesthesia used. 

The researchers found several surgical risk factors for postoperative pain, including having a large kneecap, receiving general anesthesia and experiencing more blood loss.

General anesthesia causes full-body unconsciousness, as opposed to regional anesthesia, which numbs only a specific region of the body.

"Before patients come in to the hospital, surgeons should have a thorough discussion with them regarding postoperative pain, particularly in the groups that we found tended to have more pain,” said Dr. Sculco in a press release from the Hospital for Special Surgery. “More aggressive pain management techniques may be necessary for these patients."

The studies were both presented March 11 at the American Academy of Orthopaedic Surgeons' annual meeting. Studies presented at conferences are considered preliminary until published in a peer-reviewed journal.

Review Date: 
March 11, 2014
Last Updated:
March 12, 2014