Tenosynovitis is the inflammation of a tendon and the thin, protective membrane that surrounds it, called a synovial sheath. Joints in the hands, wrists, and feet are most susceptible to tenosynovitis.
Tendons connect muscles to bones and are essential for joint movement. When a muscle contracts, its tendon pulls on the bone it is attached to, causing a joint to move. When a tendon moves, it slides underneath its synovial sheath.
If a synovial sheath and tendon become inflamed:
- The tissues swell. The swelling prevents the sheath and tendon from gliding easily against each other.
- The resulting friction between the tendon and sheath may lead to more inflammation, pain, and reduced range of motion in the affected joint.
Tenosynovitis is often caused by repetitive movements related to sports, work, or other daily activities. It can also be caused by a muscle strain, injury, infection, or inflammatory disease, including forms of arthritis.
Flexor tenosynovitis (trigger finger)
A growing body of research has found that flexor tenosynovitis in the hand is often associated with rheumatoid arthritis.1 In fact, using medical imaging (such as ultrasound) to screen for flexor tenosynovitis may occasionally be used to help make an RA diagnosis.2
A common name for flexor tenosynovitis is trigger finger.
de Quervain’s tenosynovitis
This condition occurs when tendons at the base of the thumb are inflamed. People who get de Quervain’s tenosynovitis may notice the base of the thumb is painful, tender, stiff, and swollen, and the thumb and index finger may feel numb.
Tenosynovitis treatment involves resting the affected joint and possibly using a splint to limit joint movement. Other treatments include applying a cold compress and taking an over-the-counter, nonsteroidal anti-inflammatory medication (NSAID). Occasionally, occupational therapy or a cortisone injection may be recommended.
When tenosynovitis is related to a body-wide inflammatory disease, such as RA, then treating the underlying condition is also recommended.
Tendonitis, tenosynovitis, and synovitis
Arthritis-health and other sources, including Stedman’s Medical Dictionary,3 define tendonitis as inflammation of a tendon and tenosynovitis as the inflammation of both a tendon and its sheath.
Certain sources define tenosynovitis as inflammation of a tendon sheath alone.4 In reality, inflammation of tendon and tendon sheath tissues often occur together and have similar or the same treatments.
Synovitis refers to inflammation of any synovium, whether it surrounds a tendon or another structure, such as a joint.