Musculus flexor digitorum profundus
The hind-limb deep digital flexor originates from the caudal tibia, fibula, and proximal plantar tarsus. Its tendon passes over the sustentaculum tali of the calcaneus (within the tarsal sheath) and continues down the plantar aspect of the limb to insert on the flexor surface of the coffin bone (P3). It is innervated by the tibial nerve. Like its forelimb counterpart, it flexes the digit and provides important support to the fetlock and foot during stance. The hind-limb accessory check ligament is poorly developed or absent. Clinically it is less frequently the primary focus than the forelimb DDFT (deep digital flexor tendon), but lesions within the digital flexor tendon sheath or at the level of the navicular bone do occur and can cause hind-limb lameness localized to the foot.
Origin: Caudal tibia, fibula, and proximal plantar tarsus
Insertion: Palmar/plantar surface of the distal phalanx (P3)
Action: Flexes the digit; supports the hind fetlock during stance
Innervation: Tibial nerve (L5-S2)
Hind-limb DDFT lesions are diagnosed similarly (ultrasound, MRI). They may accompany other causes of hind-foot pain. The tarsal sheath can also be involved when lesions occur near the hock.
## Overview Tarsal sheath tenosynovitis is inflammation of the sheath around the deep digital flexor tendon at the hock, producing the swelling called thoroughpin. It may be primary or secondary to t
## Overview Hind foot lameness is pain originating in the hind hoof, often from the navicular region, deep digital flexor tendon, or collateral ligaments of the coffin joint. It is frequently misdiag
Hind-limb foot lameness that is hard to localize should include evaluation of the DDFT. Sudden swelling or heat along the back of the pastern or fetlock warrants ultrasound.
## Overview Tarsal sheath tenosynovitis is inflammation of the sheath around the deep digital flexor tendon at the hock, producing the swelling called thoroughpin. It may be primary or secondary to tendon injury or hock disease. Soft fluctuant swellings appear medial and lateral to the hock. Lameness is variable. ## Causes Trauma, tendon strain, or idiopathic. ## Diagnosis Ultrasound of the sheath and tendon. ## Treatment Rest and anti-inflammatories if inflamed. Address tendon lesions if present. Cosmetic cases may be left alone. ## Recovery and Prognosis Good for uncomplicated cases. ## Prevention None specific. Signs include: soft fluctuant swelling medial and lateral to the hock; variable lameness; may indicate deeper pathology
## Overview Hind foot lameness is pain originating in the hind hoof, often from the navicular region, deep digital flexor tendon, or collateral ligaments of the coffin joint. It is frequently misdiagnosed as hock or stifle pain. Improvement with plantar digital nerve blocks and worse lameness on soft footing are clues. ## Causes Navicular syndrome, soft-tissue injury within the hoof, abscess, or bruising. ## Diagnosis Lameness examination with diagnostic analgesia, radiographs, and often magnetic resonance imaging for soft-tissue detail. ## Treatment Depends on the specific lesion: shoeing, injections, rest, or surgery. Many cases are manageable. ## Recovery and Prognosis Variable by diagnosis. Many horses return to use with appropriate management. ## Prevention Balanced shoeing and appropriate workload. Signs include: chronic low-grade hind-limb lameness; improves with plantar digital nerve blocks; often worse on soft footing; may be misdiagnosed as higher-limb pain
Hind-limb DDFT lesions are diagnosed similarly (ultrasound, MRI). They may accompany other causes of hind-foot pain. The tarsal sheath can also be involved when lesions occur near the hock.
Hind-limb foot lameness that is hard to localize should include evaluation of the DDFT. Sudden swelling or heat along the back of the pastern or fetlock warrants ultrasound.
See the Deep Digital Flexor (Hind) on our interactive 3D horse model. Open 3D Model