What are tendons and tendon sheaths?
A tendon is a strong tissue that attaches a muscle to a bone. For example, the tendons that you can see on the back of your hand come from muscles in your forearm and allow you to move the bones of your fingers.
Some (but not all) tendons are covered by a sheath called the synovium. The synovium makes a tiny amount of oily fluid which lies between the tendon and its overlying sheath. The fluid helps the tendon to move freely and smoothly when it pulls on the bone to which it is attached.
What are tendinopathy and tenosynovitis and what causes them?
Tendinopathy and tenosynovitis are types of tendon injury. They can often occur together. Strictly speaking:
- Tendonitis means inflammation of a tendon. The term tendonitis is usually used for tendon injuries that involve acute injuries accompanied by inflammation.
- Tendinosis means chronic degeneration of a tendon without inflammation. The main problem is failed healing of repeated minor injuries rather than inflammation.
- Tendinopathy is a more general term than tendonitis and tendinosis and just means tendon injury, without specifying the type of injury.
- Tenosynovitis means inflammation of the sheath that surrounds a tendon. (The sheath is called the synovium.)
It is thought that inflammation of the tendon and the tendon sheath is not the whole picture in all cases. Most of the time there is overuse or several repeated small injuries or tears, to the tendon. This may initially cause some inflammation of the tendon. But, in the longer term, if these injuries continue, it can lead to tendon damage (degeneration). Doctors now feel that tendonitis and tenosynovitis should actually be called tendinosis or tendinopathy.
These injuries typically occur when tendons are overused. For example, this may be after playing a lot of sport, or overuse in the course of your work. Tenosynovitis commonly occurs around the wrist. Overuse by lots of writing, typing, assembly line work, etc, can trigger injury. This type of overuse tendon injury is also known as repetitive strain injury (RSI).
However, in some cases, there is no history of overuse of the tendon, and tendinopathy or tenosynovitis seem to occur for no apparent reason.
There are also some other causes of tendinopathy and tenosynovitis:
- Arthritis - some types of arthritis such as rheumatoid arthritis can sometimes cause inflammation of tendon sheaths as well as joints. You would normally have joint pains and swelling in addition to tendon problems.
- Infection - this is a rare cause. The infection may occur because a cut or puncture wound to the skin over a tendon may allow germs (bacteria) to get in to infect the tendon and/or tendon sheath. However, infection sometimes spreads from other parts of the body via the bloodstream to infect a tendon sheath. For example, a small number of people who have the sexually transmitted infection called gonorrhoea develop tenosynovitis as a complication.
Who develops tendinopathy and tenosynovitis?
These problems are more common in middle-aged adults and particularly in people who are quite sporty. They may be more common if your work involves repetitive movements such as writing, typing, supermarket checkout or use of a computer mouse.
Further reading and references
Andres BM, Murrell GA; Treatment of tendinopathy: what works, what does not, and what is on the horizon. Clin Orthop Relat Res. 2008 Jul466(7):1539-54. Epub 2008 Apr 30.
Childress MA, Beutler A; Management of chronic tendon injuries. Am Fam Physician. 2013 Apr 187(7):486-90.
Extracorporeal shockwave therapy for refractory tennis elbow; NICE Interventional Procedure Guidance, August 2009
Autologous blood injection for tendinopathy; NICE Interventional Procedure Guidance, January 2013
van Tulder M, Malmivaara A, Koes B; Repetitive strain injury. Lancet. 2007 May 26369(9575):1815-22.
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