Equine Desmitis (Ligament Inflammation)

Other Names

Desmitis; ligament strain; ligament sprain; suspensory desmitis; check ligament desmitis; collateral ligament desmitis.

What is Equine Desmitis?

Equine desmitis is inflammation of one or more of the ligaments that support the horse’s limb structure. Ligaments are dense, fibrous connective tissue structures that connect bone to bone and provide stability to joints and the musculoskeletal system. When a ligament is overstretched, partially torn, or ruptured — through acute trauma or cumulative repetitive stress — an inflammatory response occurs, leading to pain, swelling, and loss of function.

Ligament injuries are among the most common causes of lameness in performance horses. The suspensory ligament and the distal check ligament (accessory ligament of the deep digital flexor tendon) are most frequently affected in sport horses, though any ligament can be damaged. Proximal suspensory desmitis (PSD) — inflammation at the origin of the suspensory ligament near the knee or hock — is a particularly challenging diagnosis and a leading cause of poor performance in dressage horses and eventers.

Unlike tendon injuries, ligament injuries can be difficult to detect in the early stages, and many horses present as subtly lame or simply performing below their best before a diagnosis is confirmed.

Causes

Desmitis is caused by forces exceeding the mechanical tolerance of the ligament fibres. Contributing factors include:

Acute overstrain during intense exercise — sudden twisting, slipping, or landing awkwardly from a fence
Cumulative fatigue injury from repetitive loading without adequate rest and recovery
Poor foot balance and farriery — improper trim or shoeing alters the biomechanical load on ligaments
Conformational abnormalities — long pasterns, hyperlax fetlocks, or toe-out conformation predispose certain horses
Rapid increases in training intensity or workload
Hard or deep going (surfaces) that transmit excessive concussion or require unusual foot placement
Previous injuries creating compensatory patterns that overload adjacent structures

Symptoms and Signs

Clinical signs depend on which ligament is affected and the severity of the damage:

Lameness — ranging from mild, intermittent to severe weight-bearing lameness
Localised heat and swelling over the affected area
Pain on palpation or flexion of the relevant joint
Positive response to flexion tests in affected joints
Poor performance without obvious lameness in subtle cases of proximal suspensory desmitis
Toe-dragging or altered gait pattern
Distension of joint capsules adjacent to affected ligaments

Proximal suspensory desmitis (PSD) is notoriously difficult to detect clinically and is frequently missed at routine examination. Horses with hindlimb PSD often present as subtly but persistently lame or simply resistant and uncomfortable in collected work.

Diagnosis

Diagnosis requires a systematic lameness examination followed by appropriate imaging. Diagnostic nerve and joint blocks are used to localise the source of pain precisely. Ultrasound is the primary imaging modality for soft tissue structures and provides excellent detail on ligament architecture, fibre alignment, and the presence of core lesions or tears.

MRI — either standing low-field or under general anaesthesia — is increasingly used for complex cases, particularly where the injury involves the proximal suspensory region close to the knee or hock, or the foot where ultrasound access is limited. Radiography may reveal bone remodelling or enthesopathy (bony change at the ligament attachment site) in chronic cases.

Nuclear scintigraphy (bone scan) can highlight areas of increased bone remodelling at ligament attachment sites, which is particularly useful in PSD diagnosis.

Treatment

Treatment depends on the severity of the injury, the ligament involved, and the horse’s intended use. The cornerstone of treatment is controlled rest followed by a structured rehabilitation programme:

Initial box rest to reduce loading on the damaged structure
Cold therapy and bandaging in the acute phase to reduce swelling
NSAIDs such as phenylbutazone for pain management and to reduce inflammation
Farriery modifications — corrective shoeing to optimise foot balance and reduce stress on the injured ligament
Gradual return to controlled exercise via a phased walking programme, building incrementally over weeks to months
Extracorporeal Shock Wave Therapy (ESWT) is widely used to promote healing in chronic or enthesopathic cases
Regenerative therapies including platelet-rich plasma (PRP) and stem cell treatment are increasingly used for significant ligament injuries
Ultrasound-guided corticosteroid injections may be appropriate for specific structures, particularly the proximal suspensory region

Rehabilitation timelines for significant ligament injuries typically range from six to twelve months or longer. Serial ultrasound examination guides progression through rehabilitation stages.

Prevention

Prevention centres on reducing the risk of overloading ligamentous structures:

Regular, balanced farriery every four to six weeks
Structured training with progressive workload increases and adequate rest periods
Monitoring surfaces — avoid excessive work on very hard or very deep going
Maintaining optimal bodyweight to reduce mechanical loading
Routine monitoring of temperature and palpation of the lower limbs after exercise

Prognosis

Prognosis varies considerably by ligament injured, severity of the damage, and the horse’s intended use. Mild to moderate injuries with well-managed rehabilitation often return horses to full work. Severe injuries, particularly those involving significant core lesions or enthesopathy, carry a more guarded prognosis and may result in recurrent lameness. Hindlimb PSD has historically carried a less favourable prognosis, though improved diagnostic and treatment options have improved outcomes.

When to Call the Vet

Call your vet for any lameness that persists beyond 24 to 48 hours, localised heat or swelling in a limb without an obvious minor cause, or a horse that is consistently performing below expected levels without a clear explanation. Do not continue full work with a limb that is showing signs of heat or swelling — early intervention significantly improves outcomes.

Frequently Asked Questions

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

Recovery time depends on the ligament affected and the severity of the injury. Mild cases with appropriate management may return to work in three to six months. Significant injuries to major supporting ligaments such as the suspensory typically require six to twelve months of structured rehabilitation, and some horses require longer. Serial ultrasound examinations at regular intervals guide the rehabilitation programme.

Can desmitis be prevented with supplements?

No supplement can prevent ligament injury from mechanical overload. However, ensuring adequate protein intake to support collagen synthesis, and maintaining a healthy body weight, contributes to overall musculoskeletal resilience. Prevention is primarily about management — farriery, training progressions, and surface management — rather than supplementation.

What is the difference between desmitis and tendonitis?

Desmitis refers to inflammation of ligaments (bone to bone), while tendonitis (or tendinopathy) refers to damage to tendons (muscle to bone). Both are common in sport horses, can occur together, and require similar approaches to diagnosis and rehabilitation. The specific structure injured determines the rehabilitation timeline and the prognosis for return to work.

Is surgery ever needed for equine desmitis?

Surgical intervention is occasionally required for specific presentations — most notably proximal suspensory desmitis in hindlimbs, where neurectomy or fasciotomy may be performed in horses that fail to respond to conservative management. Surgical options have improved in recent years, but surgery is generally considered after other treatments have been exhausted.

The British Equine Veterinary Association (BEVA) offers resources on equine lameness assessment and treatment.