Equine Hock Pathologies: Reference for Vet Rehab Therapists

Bog Spavin, Bone Spavin, Capped Hocks, Thoroughpin – Hock “puffs and bumps” are common. Some are benign adaptations; others signal joint or sheath pathology that drives pain and performance loss. This article acts as a quick reference for Vet Rehab Therapists to help them differentiate between these conditions. 

Anatomy

The hock comprises the tibiotarsal (TTJ), proximal intertarsal (PIT), distal intertarsal (DIT) and tarsometatarsal (TMT) joints. TTJ is high-motion; DIT/TMT are low-motion (tolerate cartilage loss better, but OA is still painful). The tarsal sheath encases the DDFT in the tarsal canal. A subcutaneous bursa overlies the point of the hock (tuber calcanei).

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Image Credit: UC Davies Anatomy Posters, Equine anatomy forelimb and hindlimb bone posters

Bog Spavin (TTJ Effusion)

What it is: Distension of the tibiotarsal joint capsule from synovitis or effusion. In young horses, it may accompany osteochondrosis; in mature horses, it may be caused by repetitive loading, early OA, or synovial irritation.

Presentation: A soft, fluctuant swelling at the front or medial and lateral aspects of the hock; lameness ranges from absent to mild. Asymmetry, heat, pain, or reduced flexion suggests active pathology.

Differentials: Thoroughpin (occurs in the tarsal sheath), medial or lateral plantar pouches (mis-identified), TTJ OA, OCD lesions.

Diagnostics (vet-led): Lameness exam with or without flexion tests, radiographs or US imaging; consider joint block/IA therapy trial where appropriate.

Management (overview): Treat the primary cause (OCD/OA/synovitis). Evaluate and adjust surfaces to keep them consistent and firm but neither deep nor hard; progressive loading through exercise; monitor size as workload progresses.

Benign, symmetrical effusions may be cosmetic. Painful or hot effusions need a plan.

Bone Spavin (DIT/TMT OA)

What it is: Osteoarthritis of the distal intertarsal and tarsometatarsal joints (both are low-motion joints). Degeneration can be slowly progressive yet clinically significant.

Presentation: Horses may be stiff at the start of work then warm out of the stiffness early on; reduced impulsion behind; shortened cranial phase of the hind limb; difficulty with collected work, lateral movements and transitions. Often chronic, low-grade dysfunction or lameness is present.

Differentials: Proximal Suspensory Desmitis pain, stifle pathology, sacroiliac joint discomfort, hoof imbalance, or pain originating from the hind hoof.

Diagnostics (vet-led): Localisation with distal hock joint blocks; radiographs (visible changes may lag behind clinical signs); scintigraphy or CT when findings remain inconclusive.

Management
• Medical: OA pain management principles: NSAIDs and Intra-articular therapies can be utilised.
• Farriery: Restore mediolateral balance; facilitate early breakover; maintain heel support; avoid long-toe-low-heel.
• Rehab & load: Implement a progressive loading therapeutic exercise plan. Avoid deep footing and tight turns early on.
• Advanced: Facilitated chemical or surgical arthrodesis for refractory cases.

Prognosis: Good for many horses to return to useful work.

Capped Hocks (Calcanean Bursitis/Contusion)

What it is: Swelling over the point of the hock (tuber calcanei) due to direct trauma or repeated pressure (kicking walls, lying on hard surfaces, travel rub). Usually a subcutaneous bursal enlargement although it may fibrose.

Presentation: Swelling over the point of the hock which may be warm and tender acutely, then firm and non-painful later. Performance is usually unaffected unless pain or concurrent injury exists.

Differentials: Septic bursitis; SDFT or gastrocnemius involvement at the calcaneus; curb (Long Plantar Ligament Desmitis).

Diagnostics (vet-led): Clinical exam; US if deeper structure involvement is suspected; rule out sepsis if painful, hot and systemically unwell. 

Management
Remove the cause (shallow bedding, boots causing pressure, kicking out at walls); protect the area during travel; provide brief rest when pain is present; cryotherapy or compression therapy can be used acutely.

Septic cases need prompt veterinary care.

Thoroughpin (Tarsal Sheath Tenosynovitis)

What it is: Distension of the Deep Digital Flexor Tendon (DDFT) tarsal sheath in the tarsal canal. The swelling can shift medially and laterally with palpation. Thoroughpin may be incidental, but it may also reflect tendon or sheath irritation.

Presentation: Soft, fluctuant swelling behind and above the hock; often bilateral and non-painful; lameness is absent or mild unless an active tenosynovitis or DDFT pathology exists.

Differentials: Bog spavin (TTJ pouch); annular ligament constriction; DDFT lesions within the tarsal sheath.

Diagnostics (vet-led): US of the sheath and tendon; consider sheath block or tenoscopy where warranted.

Management  
If non-painful, monitor and manage workload and surfaces while optimizing hoof balance. If painful and effusive: treat the primary pathology or cause (medical options per vet), then add progressive loading rehab strategies.

Curb (Long Plantar/Plantar Tarsal Ligament Desmitis)

What it is: Strain or inflammation of the long plantar (plantar tarsal) ligament along the plantar aspect of the hock, just distal to the point of the hock. Often linked to repetitive overload and poor conformation such as sickle hocks or cow hocks.

Presentation: Firm or thickened swelling along the plantar aspect of the hock; may be warm and tender acutely with mild to moderate lameness that improves with rest. Chronic cases often leave a cosmetic thickening with little or no pain.

Differentials: SDFT or gastrocnemius tendinopathy at the calcaneus; bone spavin pain referred caudally; thoroughpin (tarsal sheath effusion); capped hock; proximal suspensory desmitis.

Diagnostics (vet-led): Clinical exam and US to assess the ligament and adjacent tendons; radiographs to rule out avulsion and calcification; consider advanced imaging if needed.

Management

• Acute (2–6 wks): Relative rest, cryotherapy 48–72 h, NSAIDs as indicated; light compression or bandaging if tolerated; remove aggravating factors (kicking walls, deep footing).
• Farriery: Ensure mediolateral and dorsoplantar balance; avoid long-toe-low-heels that increase hindlimb lever arms.
• Rehab & load: Progressive loading through therapeutic exercise.
• Adjuncts (case-dependent): Shockwave or biologics per vet for refractory desmitis.

Prognosis: Generally good with load modification and time; chronic thickening may persist as a blemish. Recurrence risk rises with poor conformational and poor footing.

Conclusion

For hock pathology – bog spavin, bone spavin, capped hock, thoroughpin, curb – the fundamentals don’t change: balance the foot, respect conformation, manage load, refine movement, and work as a vet–farrier–therapist team. Remember the mechanics: the hock is a major load-transfer and energy-storage hub. Western sliding stops and spins add high shear and rotational stress to the distal joints and long plantar ligament; jumping concentrates force at take-off; dressage collection and lateral work increase cyclical compressive and torsional loads; driving imposes sustained, repetitive load on firm surfaces. Matching trimming and shoeing practices with progressive conditioning to these sport-specific demands (while making smart surface choices) redistributes stress, reduces signs, and slows progression over time.