Bit & Bridle

Equine Proximal Suspensory Desmitis

Other Names

  • Proximal suspensory desmopathy (PSD)
  • High suspensory disease
  • Suspensory ligament injury
  • Hindlimb proximal suspensory desmitis

What is Equine Proximal Suspensory Desmitis?

Proximal suspensory desmitis (PSD) is inflammation and injury to the proximal (upper) origin of the suspensory ligament — a critical supporting structure of the horse’s limb that runs from the back of the cannon bone, around the fetlock, and attaches to the pastern. The proximal portion of the ligament, where it originates at the back of the cannon bone just below the carpus (foreleg) or tarsus (hindleg), is the most commonly injured site.

PSD is one of the most prevalent soft tissue injuries in sport horses and is a significant cause of hindlimb lameness and poor performance. It is particularly challenging to manage because the ligament is under constant load, healing is slow, and the condition is frequently bilateral — affecting both hindlimbs simultaneously, which can make lameness difficult to detect until both sides are evaluated separately.

Hindlimb PSD is more common than forelimb PSD and presents a particular diagnostic challenge because the affected horse may not appear obviously lame but instead shows subtle gait changes, reluctance to work, or deteriorating performance. For related conditions affecting the horse’s soft tissues, see our entry on Equine Tendinitis.

Causes

PSD results from repetitive mechanical overload of the suspensory ligament at its origin. Key risk factors include:

  • Conformation — straight, upright hock conformation places greater stress on the proximal suspensory ligament during weight-bearing and push-off; horses with this conformation are significantly over-represented in PSD cases
  • Discipline and training demands — dressage horses, eventers, and showjumpers that repeatedly collect, extend, and push off the hindlimbs are at higher risk
  • Fatigue — as muscles tire, ligaments absorb greater dynamic forces, increasing injury risk
  • Poor footing — deep, inconsistent, or slippery surfaces increase the loading stress on the suspensory apparatus
  • Cumulative microtrauma — PSD often develops insidiously through repeated submaximal stress rather than a single traumatic event
  • Neurogenic atrophy — in some hindlimb PSD cases, there is concurrent or underlying damage to the deep branch of the lateral plantar nerve, leading to denervation of the ligament and subsequent weakening. This neurogenic form is more refractory to conservative treatment.

Symptoms and Signs

Clinical signs in hindlimb PSD are often subtle and may be misinterpreted as back pain, hock arthritis, or general stiffness:

  • Reduced hind impulsion or engagement in dressage horses
  • Shortened stride behind
  • Asymmetric muscle development — the gluteal and back muscles on the affected side may show atrophy
  • Reluctance to canter on a particular lead
  • Mild bilateral hindlimb lameness that worsens on a circle, particularly on harder surfaces
  • Pain on deep palpation of the proximal cannon bone (the ligament origin) in the hindlimb
  • Swelling may be absent, particularly in the hindlimb where the ligament lies deep within the cannon groove

Forelimb PSD tends to produce more obvious lameness and is often associated with swelling that is palpable on examination.

Diagnosis

Diagnosis of PSD — particularly hindlimb PSD — requires a systematic approach and is often challenging:

  • Lameness examination — trotting on a straight line and on a circle on both hard and soft surfaces; flexion tests of the distal limb and hock can exacerbate signs in hindlimb PSD
  • Diagnostic nerve blocks — perineural anaesthesia of specific nerves is used to localise the source of lameness. For hindlimb PSD, a high plantar nerve block or a specific proximal suspensory block can confirm involvement.
  • Ultrasound — essential for assessing the structure of the proximal suspensory ligament. Cross-sectional area, echogenicity, and fibre alignment are evaluated. Note that the hindlimb proximal suspensory can be difficult to image due to its depth in the cannon groove.
  • MRI — superior for complex or refractory cases, particularly where the relationship between the bone, ligament, and neural structures needs to be assessed. Standing low-field MRI has improved access to this modality.
  • Radiography — used to assess the palmar or plantar third metacarpal or metatarsal bone for periosteal changes (enthesophyte formation) at the ligament origin, which may indicate chronicity

Treatment

Treatment depends on the severity of the lesion and whether a neurogenic component is present:

  • Rest and controlled exercise rehabilitation — the foundation of treatment. Duration and progression are guided by serial ultrasound findings. Rest alone is rarely sufficient; a structured return-to-work programme is essential.
  • Extracorporeal shockwave therapy (ESWT) — widely used in desmitis treatment; promotes healing and reduces pain, particularly useful in the proximal suspensory region where direct injection is technically challenging
  • Intralesional therapies — platelet-rich plasma (PRP), bone marrow concentrate, or stem cell injection directly into the lesion to stimulate healing. Requires ultrasound guidance.
  • Corticosteroid injection — periligamentous injection of corticosteroids can reduce inflammation and pain, particularly useful when swelling and acute inflammation are present. Intralesional injection should be avoided as it can weaken ligament tissue.
  • Surgical neurectomy and fasciotomy — for hindlimb PSD with a confirmed neurogenic component, surgical deep branch neurectomy (cutting the nerve supplying the ligament) combined with plantar fasciotomy (releasing the deep fascial covering) has shown promising results, particularly in cases refractory to conservative management
  • Corrective shoeing — raising the heel with wedge pads reduces the load on the suspensory ligament during rehabilitation

Prevention

While not all cases can be prevented, the following reduce risk:

  • Train on consistent, appropriate surfaces — avoid repeatedly working on deep or uneven going
  • Build fitness gradually and avoid sudden increases in collection work or jumping intensity
  • Assess conformation at purchase — horses with upright hock conformation are higher risk for PSD
  • Palpate the proximal suspensory region regularly for heat or sensitivity
  • Ensure appropriate farriery — correct heel balance reduces abnormal loading
  • Avoid training fatigued horses, particularly in disciplines requiring significant hind engagement

Prognosis

Prognosis varies with the severity and chronicity of the lesion and the presence of neurogenic involvement. Acute, well-managed forelimb PSD often carries a good prognosis for return to work. Hindlimb PSD has a more guarded prognosis — particularly bilateral cases and those with neurogenic atrophy. In one study of dressage horses with hindlimb PSD treated conservatively, fewer than 50% returned to their pre-injury level of performance. Surgical neurectomy and fasciotomy has improved outcomes in selected cases, with some studies reporting return-to-work rates above 70% in appropriately selected horses.

When to Call the Vet

  • Your horse shows subtle hindlimb lameness, reduced engagement, or deteriorating dressage scores that have not responded to rest
  • The horse is short behind, refuses leads, or shows asymmetric muscle development over the hindquarters
  • You notice heat or swelling in the cannon region of any limb
  • Performance issues persist despite apparent soundness at rest
  • You want a baseline imaging assessment of a high-performance horse’s soft tissue structures

Frequently Asked Questions

How long does recovery from proximal suspensory desmitis take?

Recovery is typically prolonged. Mild cases managed conservatively may return to work within four to six months. Moderate to severe cases, particularly in the hindlimb, often require 12–18 months of controlled rehabilitation. Horses that have undergone surgical treatment require similar timelines, though outcomes can be better in appropriately selected cases. Serial ultrasound assessments guide the return-to-work timeline.

Can PSD be confused with hock arthritis?

Yes — hindlimb PSD and distal hock joint (bone spavin) arthritis can produce very similar signs: shortened stride behind, reluctance to engage the hindlimbs, and worsening on a circle. Systematic nerve blocking is essential to differentiate the two. A positive response to a specific proximal suspensory block, combined with imaging findings, confirms PSD rather than hock pathology.

Is bilateral hindlimb PSD common?

Yes, bilateral involvement is surprisingly common in hindlimb PSD — studies suggest up to 50% of hindlimb PSD cases are bilateral. Because both limbs are equally affected, the horse may not show a classic head-nod or obvious lameness, instead presenting with a generally poor, stilted gait. Each limb must be assessed independently, often under nerve block, to fully characterise the problem.

What disciplines are highest risk for PSD?

Dressage horses are particularly over-represented, largely due to the repeated collection, extension, and lateral work that places high demands on the proximal suspensory. Eventers and showjumpers are also commonly affected. Horses working at higher levels are at greater risk due to both the intensity of the work and the conformational selection pressure for horses with straighter hind limb angulation. See our horse terminology guide for more on the suspensory apparatus.