Osteoarthritis (OA) is the most common form of arthritis and affects approximately 30 million Americans. The underlying pathology is altered biochemical changes in cartilage- the gristle that caps the ends of long bones. Cartilage consists of cells called chondrocytes that produce a matrix. The chondrocytes sit inside this matrix, much like grapes inside gelatin.

With the development of OA, the chondrocytes no longer function properly. In addition, inflammatory changes occur within the joint. The end result is progressive and gradual loss of cartilage- leading to altered mechanics. Pain develops as a result of a number of factors including inflammation of the lining of the joint, stimulation of pain receptors in the joint capsule, and stretching of ligaments and tendons due to the altered biomechanics.

While, OA tends to affect weight-bearing joints such as the neck, low back, hips, and knees, the area that seems to be responsible for most visits to a rheumatologist's office is OA of the knee.

Conservative OA of the knee treatment consists of a comprehensive program incorporating patient education, weight loss, exercise, non-steroidal-anti-inflammatory drugs, glucocorticoid (cortisone injections), and viscosupplementation (injections of lubricant material).

In a previous article, I discussed the use of bracing for OA of the knee, which is another conservative measure.

In this article I discuss a little-known but very effective means of reducing knee pain called the lateral wedge insole.

Lateral wedged insoles are aimed at patients with varus deformity knee OA. A varus deformity means the patient has "bow-legs". Patients with varus knee deformities due to OA have significant pain involving the medial (inside) part of the knee.

A number of studies have demonstrated that the use of the lateral wedge insole, by lifting the outside of the foot, leads to valgus angulation of the ankle, resulting in slight correction of the varus knee deformity.

Measures that many studies have included are subjective daytime pain, night time pain, length of time required to walk 50 feet, and reduction in need for non steroidal anti-inflammatory drugs.

Different types of wedges are available. Some wedges are simply inserted inside a shoe. Other wedges come with a strap that provides stability of the wedge inside the shoe.

According to one of the authors responsible for the development of a popular wedged insole device, "The prevalence of knee OA in our society is increasing due to the escalating proportion of elderly persons. A conservative therapy such as the use of an insole that provides a low-cost complement or alternative to surgical treatment would be a very useful adjunct to the care of patients with knee OA and would benefit the health economy."

[Toda Y and Tsukimura N. Randomised trial to compare the clinical effects of an insole with subtalar strapping and knee support with hinged struts for patients with varus deformity osteoarthritis of the knee. Arthritis Rheum 2004; 50 (9) (supplement).

Toda Y and Tsukimura N. A six-month follow-up of a randomised trial to compare the efficacy of a lateral wedge insole with subtalar strapping and an in-shoe lateral wedged insole in patients with varus deformity osteoarthritis of the knee. Arthritis Rheum 2004; 50 (9) (supplement)].

While some detractors point to flaws in study design, abundant anecdotal evidence as well as the multiplicity of studies pointing towards effectiveness, suggest that these insoles should at least be given a try.