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Pig tenosynovitis (Image sourced from Bristol Biomed Image Archive with permission)

Tenosynovitis refers to inflammation of the synovial membrane and the fibrous layer of the tendon sheath. It is characterised by distension of the sheath due to synovial effusion and is most commonly seen in horses.

Various types of tenosynovitis occur:

septic (infectious)

Idiopathic Tenosynovitis

This refers to the distention of the synovial sheath, usually in young animals, in which the cause is uncertain. It can be seen in the common digital extensor tendon sheath or the extensor carpi radialis tendon sheath. There is usually no identifiable pathology and no lameness and treatment is usually unnecessary.

Acute and Chronic Tenosynovitis

These are due to strain, overuse or trauma and usually seen in older animals. Tendon sheaths most commonly affected include the digital flexor tendon sheath and tendon sheaths associated with the carpus and tarsus. Defects in the Superficial Digital Flexor, Deep Digital Flexor and Suspensory Ligament can cause acute swelling in the sheath and subsequent fibrosis.


Clinical examination is usually sufficient to establish the presence of tenosynovitis, but the severity and association with lameness require further work-up.

Radiography is usually indicated to evaluate any bony trauma.

Ultrasonography is used to examine the tendons and ligaments in the affected area and identify any injuries, fibrosis, synovial problems or alterations in the synovial fluid.

CT and/or MRI can be used to identify subtle changes in soft tissue and bony structures.


Treatment is similar to cases of synovitis and osteoarthritis. This includes: rest, cold hydrotherapy, bandaging, systemic and local NSAIDs.

Systemic hyaluronan can be given to provide lubrication.

Injection of medication into the tendon sheath can be performed in refractory cases, using products such as hyaluronan or corticosteroids.

Tenoscopy may have to be performed to adequately treat any synovial lesions, tears in the deep digital flexor tendon or perform annual ligament desmotomy.

Septic Tenosynovitis

This occurs following trauma and penetration of the digital sheath. It can also follow local extension of infection or haematogenous infection.

Horses are usually markedly lame if the tendon sheath is septic.


Clinical signs and a wound over the tendon sheath are suggestive.

Radiography, and especially contrast radiography (where contrast is injected into the tendon sheath and any leakage is noted) can be very useful.

Synoviocentesis and microcopic examination for any degenerate neutrophils and intracellular bacteria is very important. The sample should also be submitted for culture and sensitivity tests in order to provide the best antibiotic cover.


Septic tenosynovitis requires systemic antibiotics: broad spectrum at first and then according to culture and sensitivity results.

Drainage and lavage of the sheath should also be performed: using several litres of sterile isotonic cystalloid fluids.

NSAIDs can be given to reduce inflammation and pain.

Antibiotics can also be injected into the tendon sheath once it has been flushed.

Open drainage may have to be considered in non-responsive cases.

Prognosis is good provided rapid treatment is given and no adhesions develop between the tendon and the sheath.

Tenosynovitis Learning Resources
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Test your knowledge using flashcard type questions
Equine Orthopaedics and Rheumatology Q&A 18


Merck and Co (2008) Merck Veterinary Manual Merial

Baxter, G. (2011) Adams and Stashak's Lameness in Horses John Wiley and Sons

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