M65: Synovitis and tenosynovitis

M65.4: Radial styloid tenosynovitis [de Quervain]

A tendon sheath inflammation may involve inflammation of the tendon and the associated tendon sheath. Tendons are made up of very firm connective tissue. Tendons attach muscles to bones. A tendon sheath is a covering for the tendon. It cushions the tendon and contains a small amount of fluid. This reduces friction between the tendon and its surroundings.

Tendon and tendon sheath inflammations can be caused by excess use or repetitive movements. The inflammation can cause scars and adhesions. As a result, the tendons are no longer able to glide in the tendon sheaths so well.

Moving the thumb may then become painful. The pain can also spread to the wrist and arm. There may also be a loss of mobility in the thumb. Your grip may then be weaker than usual.