General anesthesia and longer time in a tourniquet also appear to contribute to higher levels of pain, the study authors said.
"There is no question that pain after total knee replacement is greater than that after total hip replacement," Dr. Thomas Sculco, surgeon-in-chief at New York City's Hospital for Special Surgery, said in a hospital news release. "Many factors play a role, and our studies found that younger female patients, particularly those with post-traumatic or rheumatoid arthritis, had the highest pain scores."
Sculco and his colleagues examined the medical records of 273 patients who underwent total knee replacement procedures from 2007 to 2010.
Those who suffered the most pain during rest after surgery included: women; people aged 45 to 65; those with osteoarthritis, rheumatoid arthritis or arthritis from an injury; people who were obese; and those who had more pain when they were admitted to the hospital. But those with avascular necrosis, a disease that causes parts of bones to die, had significantly lower levels of pain, the study authors noted.
When the patients were involved in physical activity, those who were aged 45 to 65, who were obese, or who had suffered from more pain upon hospital admission had the highest levels of pain after surgery. Those with osteoarthritis or avascular necrosis, or both conditions, had lower levels of pain related to physical activity, the findings indicated.
"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," Sculco said. "More aggressive pain management techniques may be necessary for these patients."
In another study of knee replacement surgery, the researchers looked at the same medical records and determined that pain was higher among people at rest who had received general anesthesia (instead of an epidural or spinal block), those who were in a tourniquet for a longer period of time, those with more blood loss, and those with large kneecaps.
"The surgeon must be aware not to use an implant that is too large for the knee or a kneecap component that is excessive in size. In addition, the location of the joint line must be accurately positioned after the knee replacement, for if it is too high it may lead to increased pain," Sculco pointed out in the news release.
The research was scheduled to be presented March 11 at the annual meeting of the American Academy of Orthopaedic Surgeons, in New Orleans. Research presented at medical meetings should be viewed as preliminary until published in a peer-reviewed journal.
For more about knee replacement surgery, visit the U.S. National Library of Medicine.