NEWARK, Delaware—The traditional practice of postponing total knee arthroplasty as long as possible is a mistake, is driven by outdated assumptions about the durability of total knee prostheses, and is particularly harmful to women with knee osteoarthritis (OA), according to University of Delaware researchers.

Lynn Snyder-Mackler, MD, warns that postponing surgery until pain is unendurable may impair the functional recovery possible after arthroplasty. Dr. Snyder-Mackler is distinguished alumni professor in the University of Delaware's department of physical therapy.

New knees needed sooner

"Doctors typically tell patients to wait to have knee replacements until they just can't stand the pain any longer," Dr. Snyder-Mackler told Musculoskeletal Report. "The advice to put off knee replacement is bad advice, and it is worse for women than it is for men. Functionally, the patient will only be as good after knee replacement as he or she was preoperatively. The main difference is that there will be less pain after knee replacement."

The researchers studied 221 OA patients who were candidates for total knee replacements (95 men, 126 women) Physical function and disability in these patients were compared with function and disability in 44 healthy, gender, age, and body mass index-matched controls.

Functional assessments included the Medical Outcomes Study Short Form-36 (SF-36) mental and physical component scores. The effect of pain on the patient's function was assessed using the Knee Outcome Survey question, "How does pain affect the function of your knee during daily activities?" scored from 0 (prevented all activities) to 5 (had no effect on daily activities). Knee range of motion was measured with a long-axis goniometer actively in the supine position. The 6-minute walk test, timed up-and-go test, and time required to ascend and descend 12 steps were used to assess function. Burst superimposition was used to measure quadriceps strength and volitional muscle activation.

The men generally were stronger and had better knee function than the women, and these differences were magnified in the women with OA. The only functional measure that was not significantly worse for women was the Knee Outcome Survey score for pain. "Maybe women are just more stoic," Dr. Snyder-Mackler said. "They certainly were more disabled than the men in this study."

Taken together, the results suggest that women are more adversely affected by OA than men are and that women postpone arthroplasty until their OA is more advanced than their male counterparts. This difference is likely to lead to worse outcomes in women. Petterson et al¹ recommend informing potential female arthroplasty candidates for warnings about the risks of delaying knee replacement and beginning impairment-based rehabilitation well before surgery to preserve function, strength, and activation, which may help improve postoperative quality of life.

Prostheses more durable these days

The reasons for the delay in knee arthroplasty in women with OA remain speculative, but Dr. Snyder-Mackler suspects that one factor is residual concern that the new knee will wear out before the patient does, leaving few options for later intervention.

"Thinking about prosthesis wear needs to catch up with the realities of technical advances over recent years. Current prosthesis can be expected to last 20 years, and at that point we may have bionic knees or some other major advance to deploy. Also, revision surgery methods are better and are always improving. Clinicians who recommend delaying knee replacement because they are afraid the prosthesis will wear out should also consider that we are not generally talking about patients who plan to go out and run marathons. Most patients with advanced knee OA just want to be able to go up and down stairs comfortably," Dr. Snyder-Mackler said.

The study, which was funded by a $1,125,000 grant from the National Institutes of Health, was conducted by Dr. Snyder-Mackler and collaborators Stephanie Petterson, PhD (now a senior lecturer at the University of East London) and orthopaedic surgeons Leo Raisis, MD, and Alex Bodenstab, MD, from First State Orthopaedics in Newark, Delaware.

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