Bit & Bridle

Equine Tendinitis

Other Names

  • Tendonitis
  • Tendon strain
  • Bowed tendon
  • Core lesion
  • Superficial digital flexor tendon (SDFT) injury
  • Deep digital flexor tendon (DDFT) injury

What is Equine Tendinitis?

Equine tendinitis is inflammation and structural damage to one or more of the tendons in a horse’s limb, most commonly the superficial digital flexor tendon (SDFT) on the palmar (back) surface of the forelimb. Tendons are dense fibrous structures that connect muscles to bones, transmitting the force of muscular contraction to generate movement. In horses, the SDFT is under enormous mechanical load — particularly in galloping and jumping — making it one of the most injury-prone structures in the equine athlete.

Tendinitis is most prevalent in racehorses and sport horses but can occur in any horse engaged in strenuous work. The condition can range from minor inflammatory episodes with no visible swelling to severe core lesions where a significant proportion of the tendon fibres are disrupted — the so-called “bowed tendon” visible as a swelling along the back of the cannon bone.

Recovery is often prolonged, and re-injury is common, making tendinitis one of the most career-limiting conditions in performance horses. See also our entry on Equine Proximal Suspensory Desmitis for information on a closely related soft tissue injury.

Causes

Tendinitis results from mechanical overload of the tendon fibres, leading to partial or complete disruption of the collagen matrix. Key contributing factors include:

  • High-speed work — the SDFT experiences peak loads during fast work, with forces exceeding the tendon’s elastic limit causing fibre failure
  • Fatigue — as muscles tire during prolonged exercise, tendons absorb more of the load, increasing injury risk
  • Poor going — deep, soft, or uneven surfaces increase tendon strain significantly
  • Inadequate conditioning — sudden increases in training intensity without adequate preparation
  • Poor conformation — long pasterns, offset knees, and other conformational faults increase tendon loading
  • Improper shoeing — inappropriate heel height or shoe type can alter biomechanics and increase tendon stress
  • Pre-existing subclinical damage — continuing to train through minor inflammatory episodes leads to cumulative damage
  • Ageing — older tendons have reduced elasticity and repair capacity, increasing susceptibility to injury

Symptoms and Signs

Clinical signs vary depending on the severity and acuity of the injury. In the acute phase:

  • Heat along the back of the cannon bone
  • Swelling and oedema in the tendon region
  • Pain on palpation — the horse may flinch when the tendon is squeezed gently
  • Lameness, which may be mild to severe depending on the extent of damage
  • The classic “bowed” appearance — a visible convex bulge along the palmar aspect of the cannon bone in more severe cases

In chronic cases, the acute inflammation subsides and the tendon may feel firm and thickened rather than hot. A horse may appear sound at rest but show decreased performance and recurring low-grade lameness under work.

Diagnosis

Clinical examination provides the initial assessment, but ultrasonography is the definitive diagnostic tool for equine tendinitis:

  • Physical examination — palpation for heat, swelling, and pain; assessment of lameness at walk, trot, and on a circle
  • Ultrasound — the gold standard for assessing tendon injury. Allows visualisation of the tendon cross-section, identification of core lesions (hypoechoic or anechoic areas), measurement of the cross-sectional area, and monitoring of healing over time. Baseline ultrasound at diagnosis is essential to quantify the injury.
  • MRI — provides superior soft tissue detail, particularly for complex injuries involving the DDFT within the hoof capsule, but is more expensive and often requires referral to a specialist centre
  • Nerve and tendon sheath blocks — may be used to localise the source of lameness before imaging

Serial ultrasound examinations at regular intervals (typically every four to six weeks) are used to monitor healing and guide the return to work programme.

Treatment

Treatment depends on the severity of the injury and the stage of healing. The following approaches are used:

  • Immediate rest and cold therapy — in the acute phase, cold water hosing, ice packs, and cold bandages reduce inflammation and limit further damage
  • Non-steroidal anti-inflammatory drugs (NSAIDs) — phenylbutazone or flunixin reduce pain and systemic inflammation. Generally used short-term in the acute phase.
  • Controlled exercise rehabilitation — a gradual, ultrasound-guided return to work programme is essential. Returning to full work too quickly is the most common cause of re-injury.
  • Tendon splitting — in cases with a distinct core lesion, a needle is used to create channels within the lesion to reduce intratendinous pressure and promote drainage. Typically performed under ultrasound guidance.
  • Platelet-rich plasma (PRP) — injection of concentrated growth factors from the horse’s own blood into the lesion to stimulate healing. Evidence is promising but not yet definitive.
  • Mesenchymal stem cell therapy — bone marrow or adipose-derived stem cells are injected into the lesion to promote tissue regeneration. Considered one of the most promising advanced therapies, with several studies showing reduced re-injury rates.
  • Extracorporeal shockwave therapy (ESWT) — acoustic shockwaves applied externally to stimulate healing, particularly useful in chronic tendon disease
  • Supportive shoeing — raised heel shoes or wedge pads reduce tension on the SDFT during healing

Intratendinous corticosteroid injections are contraindicated and can cause further tendon degradation.

Prevention

Reducing the risk of tendinitis requires careful management of training load and the horse’s environment:

  • Introduce new work gradually — avoid sudden increases in speed, distance, or intensity
  • Train on good-quality, consistent surfaces where possible
  • Monitor body condition — excess weight increases load on the tendons
  • Use supportive boots or bandages during high-intensity work
  • Palpate tendons after every session — warmth or thickening warrants rest and veterinary review
  • Ensure appropriate farriery — correct hoof balance reduces abnormal tendon loading
  • Allow adequate warm-up and cool-down before and after work
  • Consider nutritional support such as omega-3 fatty acids and targeted tendon supplements during heavy training periods

Prognosis

The prognosis for equine tendinitis varies significantly with the severity of the injury. Minor tendinitis treated promptly with appropriate rest and rehabilitation can resolve fully. Moderate to severe core lesions carry a guarded prognosis — particularly in high-performance animals — as scar tissue formed during healing is biomechanically inferior to normal tendon tissue and prone to re-rupture. Studies suggest that up to 80% of racehorses that suffer SDFT tendinitis re-injure the tendon. Advanced biological therapies (PRP, stem cells) aim to improve tissue quality and reduce re-injury rates, but outcomes remain variable.

When to Call the Vet

  • You notice heat, swelling, or pain along the back of your horse’s cannon bone, even if the horse is not visibly lame
  • Your horse shows sudden onset lameness during or after exercise
  • There is a visible bowing or convex swelling along the palmar cannon region
  • Your horse has previously had tendon injury and you notice any recurrence of signs
  • You wish to establish a rehabilitation protocol or discuss advanced treatment options

Frequently Asked Questions

How long does it take for a horse to recover from tendinitis?

Recovery time depends on the severity. Minor cases may allow a return to light work within three to four months with careful management. Severe core lesions typically require 12–18 months of rest and graduated rehabilitation before returning to full work. Returning a horse to competition prematurely is the most common reason for re-injury. Always follow ultrasound-guided return-to-work programmes rather than using an arbitrary timeline.

Is a bowed tendon the same as tendinitis?

A bowed tendon is a more severe form of tendinitis, where the swelling from inflammation and fluid accumulation creates a visible convex bulge along the palmar cannon bone. Not all tendinitis cases result in a visible bow — many are only detectable on ultrasound — but all bowed tendons indicate significant underlying tendon damage requiring veterinary management.

Can horses return to full competition after tendinitis?

Many horses do return to competition, but the rate varies by sport and injury severity. With appropriate treatment and a structured rehabilitation programme, including advanced biological therapies, return-to-work rates in sport horses can be favourable. Racing, however, involves extremely high tendon loads and re-injury rates are significantly higher than in lower-intensity disciplines. Discuss realistic expectations with your vet based on the specific injury and your horse’s intended use.

Should I use boots to prevent tendon injuries?

Supportive boots can reduce the risk of impact injuries and provide some proprioceptive benefit, but they are not definitively proven to prevent tendinitis from overload. The most effective preventive measures are appropriate training management, good footing, and regular palpation to detect early inflammatory changes. See our horse terminology guide for more on equine tendon anatomy.