Os tarsale I et II (T1+T2)
In the horse the first and second tarsal bones are typically fused into a single small bone (T1+T2) on the medial side of the distal tarsal row. It articulates proximally with the central tarsal bone and distally with the second metatarsal (medial splint) bone. This fused bone is part of the distal intertarsal and tarsometatarsal joints and is commonly involved in bone spavin (osteoarthritis of the distal tarsal joints). Bone spavin is one of the most common causes of hind-limb lameness. The distal tarsal joints are low-motion joints that are subject to compression and shear; degenerative changes, joint-space narrowing, and periarticular new bone are frequent radiographic findings.
The hock has multiple joint compartments. Bone spavin most often affects the distal intertarsal and tarsometatarsal joints. Diagnosis is by lameness exam, joint blocks, and radiography. Many horses remain serviceable with management (shoeing, medication, controlled exercise).
## Overview Bone spavin is osteoarthritis (degenerative joint disease) of the distal tarsal joints, principally the distal intertarsal and tarsometatarsal joints. Repeated compression and rotation da
## Overview Distal tarsal osteoarthritis, commonly called bone spavin, is degenerative joint disease of the lower hock joints (distal intertarsal and tarsometatarsal joints). It is a frequent cause o
Hind-limb lameness that is worse after rest or that improves with exercise, especially with a shortened stride or toe-dragging, may involve the lower hock. Have a veterinarian localize the pain rather than assuming “hock.”
## Overview Bone spavin is osteoarthritis (degenerative joint disease) of the distal tarsal joints, principally the distal intertarsal and tarsometatarsal joints. Repeated compression and rotation damage cartilage, narrow the joint spaces, and stimulate new bone formation. The result is progressive hind-limb lameness that is one of the most common causes of performance limitation in sport horses. ## Causes Repetitive concussion, conformational faults (straight or sickle hocks), and athletic activities that heavily load the hocks (jumping, dressage, western performance) are the main drivers. Mineral imbalances have been suggested but evidence is limited. ## Diagnosis History of gradual hind-limb lameness that may warm out of, positive flexion tests, and a characteristic “stabbing” or short stride are suggestive. Radiographs show joint-space narrowing, sclerosis, and periarticular new bone. Diagnostic analgesia of the distal tarsal joints confirms the source of pain. ## Treatment Non-steroidal anti-inflammatory drugs, intra-articular corticosteroids, corrective shoeing, and workload modification are first-line measures. Chemical or surgical arthrodesis (facilitated ankylosis) can be considered when medical management fails and the goal is pain-free fusion of the low-motion joints. ## Recovery and Prognosis Many horses remain useful with medical management. Complete fusion, whether spontaneous or surgical, can restore comfort. Advanced bilateral disease may ultimately limit athletic career length. ## Prevention Selection for good hock conformation, balanced shoeing, and sensible training progression reduce risk but cannot eliminate it in high-level athletes. Signs include: gradual hindlimb lameness; shortened stride or toe dragging; positive hock flexion test; bony enlargement on the medial lower hock in advanced cases; stiffness after rest
## Overview Distal tarsal osteoarthritis, commonly called bone spavin, is degenerative joint disease of the lower hock joints (distal intertarsal and tarsometatarsal joints). It is a frequent cause of hind-limb lameness in performance horses. Affected horses show stiffness, shortened stride, and positive flexion tests. ## Causes Repetitive loading, conformational faults (straight or sickle hocks), and age-related cartilage wear. ## Diagnosis Lameness examination, hock flexion test, diagnostic analgesia, and radiographs showing osteophytes, joint-space narrowing, or ankylosis. ## Treatment Intra-articular corticosteroids or other medications, systemic anti-inflammatories, corrective shoeing, and workload adjustment. Many horses improve and remain useful. ## Recovery and Prognosis Fair to good for comfort and lower-level work. Advanced cases may require ongoing management. ## Prevention Balanced shoeing and sensible training. Early treatment of stiffness. Signs include: hind-limb stiffness; shortened stride; positive hock flexion; reluctance to collect or engage the hindquarters; radiographic changes in the lower hock joints
The hock has multiple joint compartments. Bone spavin most often affects the distal intertarsal and tarsometatarsal joints. Diagnosis is by lameness exam, joint blocks, and radiography. Many horses remain serviceable with management (shoeing, medication, controlled exercise).
Hind-limb lameness that is worse after rest or that improves with exercise, especially with a shortened stride or toe-dragging, may involve the lower hock. Have a veterinarian localize the pain rather than assuming “hock.”
See the First & Second Tarsal Bones (Right, fused) on our interactive 3D horse model. Open 3D Model