JULY 5, 2002

Media advisory:  To contact D. Casey Kerrigan, MD, MS, call Joanne Constantine at (312) 464-6290.

Special Insole Lessens Pain, Progression of Knee Arthritis

CHICAGO—Wedged insoles may ease the pain and progression of knee osteoarthritis by reducing the twisting force exerted on the knee during walking, according to an article in the July issue of the Archives of Physical Medicine and Rehabilitation.

D. Casey Kerrigan, MD, MS, professor and chair of physical medicine and rehabilitation at the University of Virginia in Charlottesville, and colleagues studied 15 patients with painful, radiographically confirmed medial compartment (middle) knee osteoarthritis to compare the effectiveness of a lateral-wedge insole and an even thickness control insole.

“How you support your feet is vitally important to the progression of osteoarthritis,” Dr. Kerrigan said in a separate interview.

The 15 patients were studied as they walked in their personal comfortable shoes without a wedge, with two different even thickness insoles and with a 5° lateral-wedge insole and a 10° lateral-wedge insole. The lateral-wedge insole is thin at the instep and gradually increases to the fullest elevation at the outside of the foot, thus shifting the relationship of the body’s weight in respect to the knee.

The researchers found that lateral-wedge insoles reduced twisting of the knee, also called varus torque, during walking. “Compared with having no insole, the 5° lateral-wedge insole was associated with an almost six percent overall reduction in knee varus torque,” the researchers write. “Our significant differences between the lateral wedges and control insoles show that the effect of the wedge is the result of directly altering the knee joint biomechanics rather than being merely the result of insole cushioning. Moreover, the fact that there were no differences in temporal parameters between the conditions supports the conclusion that the reduced measured knee varus torque with the lateral wedge was not merely the result of a slower walking speed or stride length.”

“The lateral-wedge insole is a conservative treatment that can be useful at any point in disease progression. It will help a newly diagnosed patient as well as someone who has had osteoarthritis of the knee for years,” said Dr. Kerrigan in a separate interview.

Dr. Kerrigan advises people with knee osteoarthritis to consult a physical medicine and rehabilitation (PM&R) physician: “A thorough evaluation will be made to ensure that you have the correct diagnosis of knee osteoarthritis, which is extremely important. We also help manage osteoarthritis with personalized exercise prescriptions that help improve function, promote weight loss and strengthen knee muscles without putting undue force on the knee compartment. A PM&R physician will devise a personalized program especially for you in combination with the appropriate shoe insole.”

“Eventually, most people develop arthritic changes in the medial part of the knee. Modification of shoes with insoles slow knee osteoarthritis’ progression and pain, while wearing low-heeled shoes can reduce future osteoarthritis risk. Our previous research has shown that wearing high heels increases the same twisting force reduced by the wedged insoles. I recommend half inch or lower heels,” comments Dr. Kerrigan.

Osteoarthritis is the breakdown of the cartilage covering the ends of the bones that serve as a shock absorber. As the cartilage wears away, the cushion between the bones shrinks allowing the bones to grind together.

Medial compartment knee osteoarthritis causes joint space loss in the knee compartment. This elevates knee varus torque and potentiates progressive join space loss and angulation, thus creating a vicious cycle. Consequently, rehabilitation aimed at halting this cycle by reducing varus torque may be the most effective. Reducing the torque should prevent progression of the cartilage degeneration.

The researchers encourage people with osetoarthritis of the knee to lose weight if they are overweight. Canes may be recommended to help reduce overall force through the leg. 

The lateral-wedge insole only helps people who have medial (middle) knee osteoarthritis. Unfortunately, the insole will not help those with another common form of knee osteoarthritis, patella femoral osteoarthritis, which is arthritis between the kneecap and thighbone. Those with lateral knee osteoarthritis may actually be harmed by the insole. Lateral knee osteoarthritis, which affects the outside of the knee, is present in slightly less than 10 percent of people with knee osteoarthritis. 

The Archives of Physical Medicine and Rehabilitation is the official journal of The American Academy of Physical Medicine and Rehabilitation (AAPM&R). It is co-published with the American Congress of Rehabilitation Medicine. AAPM&R is the national medical specialty society of more than 7,000 physical medicine and rehabilitation physicians, also called physiatrists. Physical medicine and rehabilitation physicians focus on restoring function. They care for patients with acute and chronic pain and musculoskeletal problems like back and neck pain, tendonitis, pinched nerves and fibromyalgia. They also treat people who have experienced catastrophic events resulting in paraplegia, quadriplegia or traumatic brain injury and individuals who have strokes, orthopedic injuries or
neurological disorders such as multiple sclerosis, polio or ALS.

(Arch Phys Med Rehabil. 2002;83:889-893)