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Shoe Insoles to Prevent Arthritis in People with Old ACL Injuries
January 22, 2004
By Stephanie Riesenman
Untreated anterior cruciate ligament (ACL) injuries often lead to osteoarthritis of the knee; but doctors in Japan say there is an inexpensive and noninvasive treatment, which fits right into the shoe, that can slow the develop of arthritis.
Doctors in the Department of Orthopaedic Surgery at Fukuoka University in Fukuoka, Japan often prescribe wedged insoles as a non-operative therapy for osteoarthritis of the knee. Several studies have shown that the insoles help to mitigate pain and slow the progression of arthritis in patients with old ACL injuries that have not been surgically repaired.
"This therapy is relatively effective in early phases of osteoarthritis and is easily applied by placing the insole in the shoe," writes Dr. Ichiro Yoshimuro and colleagues of Fukuoka University.
When an ACL ruptures and surgical repair is not selected, it typically follows a course of progressive deterioration of knee function. This weakening often leads to meniscal tears and eventual degeneration of the articular cartilage in the knee. If left untreated, the end result is osteoarthritis.
In a study published in a recent issue of the American Journal of Sports Medicine, Dr. Yoshimuro and colleagues measured the effect of insoles on the lateral thrust in knees with ACL insufficiency. Earlier studies have shown that wedged insoles help to reduce thrust when walking or running. Thrust is the stress or energy that’s put on the knee with each step. Lateral thrust—which occurs on the outside of the knee—increases significantly with ACL insufficiency.
The study included 60 people with healthy knees, and 35 patients with ACL injuries scheduled to undergo ACL reconstruction because their knees were weak and prevented them from doing daily activities. Some patients had injured their ACL’s as much as 3 years ago.
Accelerometers were attached to the legs of all study participants in order to record the medial-lateral tension of the knee while walking. The signals generated by tension on the knee were recorded on a computer. Both the control patients with healthy knees and those with injured knees walked for 3 cycles without insoles and then 3 cycles with insoles on 2 separate occasions.
The valgus insoles were made of a type of vinyl and had a flat upper surface covered with leather. The insole was thicker under the outside of the foot from the little toe to the heal. The height of the raised portion of the insole was 8 millimeters for women and 10 millimeters for men.
The peak value of lateral thrust was compared between the healthy and ACL insufficient knees, and between ACL insufficient knees with and without insoles. A lateral thrust pattern was identified in 31 of 35 knees with previous ACL injuries. When the valgus insoles were placed in their shoes, only 24 were shown to have a lateral thrust pattern. Of those who still had a lateral thrust, the amount was significantly reduced.
"Use of an insole is one possible prophylaxis for osteoarthritis in an ACL insufficient knee that does not require surgery," the researchers write.
The insoles, they say, help to reduce lateral thrust—which makes the ligaments more lax over time—and therefore slows the progression towards osteoarthritis in patients with previous ACL injuries.
An orthopedist will examine patients with ACL insufficiencies to determine if valgus insoles would be effective in relieving pain and preventing the progression of osteoarthritis.
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