Stenosing tenosynovitis of the radial styloid process is a painful condition that occurs in the radial styloid process. Although the pain is manifested in the radial styloid process, the cause is actually due to a strain on the adductor tendon of the thumb. If the strain causes inflammation of the tendon in the tendon sheath area, the inflammation becomes enlarged and the tendon becomes immobilized in the tendon sheath, resulting in stenosing tenosynovitis. More specifically, in the radial styloid tendon sheath, the tendon can become swollen and enlarged, and that enlargement is very specific, in the form of a small bulb-like nodule. If the tendon sheath is narrowed, it just so happens that the tendon mass is larger and there is an obstruction when it passes through the tendon sheath, so stenosing tenosynovitis can affect the movement of the thumb.