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Tenosynovitis in Large Animals

By C. Wayne McIlwraith, BVSc, PhD, DSc, FRCVS, DACVS, DACVSMR,

Tenosynovitis, an inflammation of the synovial membrane and usually the fibrous layer of the tendon sheath, is characterized by distention of the tendon sheath due to synovial effusion. It has a number of possible causes and clinical manifestations. The various types of tenosynovitis include idiopathic, acute, chronic, and septic (infectious). Idiopathic synovitis refers to synovial distention of tendon sheaths in young animals, in which the cause is uncertain. Acute and chronic tenosynovitis are due to trauma. Septic tenosynovitis may be associated with penetrating wounds, local extension of infection, or a hematogenous infection.

Tarsal and digital tendon sheaths of the deep digital flexor tendon, horse

Tarsal and digital tendon sheaths of the deep digital flexor tendon, horse. Illustration by Dr. Gheorghe Constantinescu.

Clinical Findings and Diagnosis:

There are varying degrees of synovial distention of the tendon sheath and lameness, depending on the severity. Horses are markedly lame in septic tenosynovitis. Chronic tenosynovitis is common in horses in the tarsal sheath of the hock (thoroughpin) and in the digital sheath (tendinous windpuffs). These two entities must be differentiated from synovial effusion of the tarsocrural and fetlock joints, respectively.


In idiopathic cases, no treatment is initially recommended. Acute cases with clinical signs may be treated symptomatically with cold packs, NSAIDs, and rest. Tenoscopic surgery is often used to treat specific conditions within the tendon sheath that give rise to tenosynovitis symptoms. Application of counterirritants and bandaging has been used in more chronic cases. Septic tenosynovitis requires systemic antibiotics and drainage. If adhesions develop between the tendon sheath and the tendon, persistent effusion and lameness is the rule.

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