Overview and Classification of Tenosynovitis

Overview

Tendons are made of dense, tightly packed fibrous tissue and are not well supplied with blood vessels. Therefore, inflammatory cell infiltration does not readily occur in the tendons themselves. However, inflammatory cell infiltration occurs relatively often in the synovium surrounding the tendon, that is, the tendon sheath.

This condition can be called tendinitis or tenosynovitis.

These terms are used to refer broadly to inflammatory diseases of the tendon sheath and tendons.

In order to change the direction of the force generated by a muscle or amplify that force, a tendon requires a pulley.

In many cases, this pulley takes the form of a fibro-osseous tunnel. The cross-sectional area of the fibro-osseous tunnel is slightly larger than that of the tendon, allowing the tendon to pass through smoothly and to maximize the efficiency of force and energy.

When inflammation occurs in the tendon sheath, it causes swelling and pain, making it difficult for the tendon to pass through the fibro-osseous tunnel; this is called tenosynovitis. Meanwhile, tenosynovitis can also occur when the fibro-osseous tunnel becomes stretched and the tendon moves out of its original position. In such cases, it is common to use a more specific term, such as tendon dislocation, rather than tendinitis.

Classification

Tenosynovitis is relatively common, to the extent that anyone may experience it several times in a lifetime. Tenosynovitis includes both bacterial and non-bacterial types, and among these, idiopathic tenosynovitis of unknown cause accounts for the majority. These are presumed to occur when scar tissue forms due to minor trauma, or when friction between the tendon and nearby tissues increases.

Idiopathic tenosynovitis takes various forms. One common form is entrapment tenosynovitis or stenosing tenosynovitis, which occurs when the pulley and tendon do not fit well together.

In addition, after a minor tear or degenerative change appears in the tendon or muscle area, the resulting symptoms may persist for several months. Problems may also arise as the tendon repeatedly rubs against an external object or as the tendon repeatedly rubs against internal bone.

Idiopathic tenosynovitis may occur through various other mechanisms that we do not fully understand. These problems are mild in the sense that they do not cause survival issues or disability, but they can cause severe pain, so they can be a serious problem for patients.

Among the non-bacterial types, a representative cause that has been identified is rheumatoid arthritis. In fact, in most patients with rheumatoid arthritis, inflammation of the tendon sheath occurs at some point during the course of the disease, and histologic examination of the tendon sheath at that time reveals rheumatoid pathological findings.

Bacterial tenosynovitis can be classified according to the type of invading bacteria, such as suppurative and tuberculous infections, and in such cases the resulting pus can easily spread along the sub-tendon sheath space.

So far, we have covered the overview and classification of tenosynovitis. In the next installment, we will look at specific tenosynovitis.

Source: Korea Disease Control and Prevention Agency, National Health Information Portal