Os carpale III (C3)
The third carpal bone (C3) is the largest of the distal row. It articulates proximally with the radial and intermediate carpal bones and distally with the third metacarpal (cannon) bone. It is the most common site of slab fractures in racehorses due to the extreme compressive forces transmitted through this bone during high-speed exercise. These slab fractures typically run in a frontal plane.
The carpus is commonly injured in racehorses. Chip and slab fractures are treated arthroscopically.
Slab fractures (very common in racehorses)
Incomplete/stress fractures
Subchondral bone sclerosis
Degenerative joint disease, also known as osteoarthritis, is the progressive breakdown of articular cartilage and the underlying bone within a joint. It is one of the most common causes of chronic lam
Slab fractures (very common in racehorses) Signs include: Consult veterinarian for specific symptoms.
Incomplete/stress fractures Signs include: Consult veterinarian for specific symptoms.
Subchondral bone sclerosis Signs include: Consult veterinarian for specific symptoms.
Degenerative joint disease, also known as osteoarthritis, is the progressive breakdown of articular cartilage and the underlying bone within a joint. It is one of the most common causes of chronic lameness in horses of all ages and disciplines and can affect any joint, though the fetlock, coffin, hock, and stifle are most frequently involved. ## What it is Osteoarthritis begins with damage to the articular cartilage, often from repetitive stress, trauma, or conformational abnormalities. As the cartilage degrades, the underlying bone becomes exposed and reactive, leading to the formation of osteophytes (bone spurs), joint capsule thickening, and synovial inflammation. Over time, the joint loses range of motion and becomes painful, resulting in lameness and reduced performance. The condition is usually progressive. While it cannot be reversed, early intervention can slow its advancement and improve comfort. It is frequently secondary to previous joint injury, developmental orthopedic disease, or chronic overload. ## Signs and symptoms - Progressive lameness that worsens with work - Joint swelling or effusion - Reduced range of motion and stiffness, especially after rest - Pain on flexion of the affected joint - Shortened stride and reluctance to perform certain movements - Muscle atrophy around the affected limb in chronic cases - Bony enlargement around the joint in advanced osteoarthritis ## Causes and risk factors Degenerative joint disease develops from repetitive trauma, acute injury, poor conformation, or developmental issues that place abnormal stress on the joint. Risk factors include intense training or competition at a young age, previous joint trauma or surgery, obesity, and genetic predisposition. Horses in high-impact disciplines and those with conformational faults are more commonly affected. ## How it is diagnosed Diagnosis involves a combination of clinical examination, flexion tests, diagnostic analgesia, and imaging. Radiographs are the most common tool and can show joint space narrowing, osteophytes, and subchondral bone changes. Ultrasound helps evaluate soft tissues and joint effusion. In some cases, MRI or CT provides more detailed information about cartilage and bone. Joint fluid analysis may be performed when infection or other inflammatory conditions are suspected. ## Treatment and management Treatment is aimed at reducing pain and inflammation while slowing disease progression. Common approaches include systemic anti-inflammatories (such as phenylbutazone or firocoxib), joint injections (corticosteroids, hyaluronic acid, or regenerative therapies such as PRP or stem cells), and controlled exercise programs. Corrective farriery and weight management are important supportive measures. In advanced cases, surgical options such as arthrodesis may be considered for low-motion joints. ## When to call the vet Contact your veterinarian if your horse shows persistent or progressive lameness, joint swelling, or stiffness that does not resolve with rest. Early diagnosis and treatment offer the best chance of slowing the progression of degenerative joint disease. ## Prevention Prevention focuses on minimizing joint stress through proper conditioning, maintaining ideal body weight, and addressing conformational issues when possible. Prompt treatment of acute joint injuries and careful management of young horses in training help reduce the risk of early-onset osteoarthritis. ## Frequently asked questions **Can degenerative joint disease be cured?** No. It is a progressive condition. Treatment focuses on managing pain and slowing progression rather than reversing the disease. **Are joint injections safe for long-term use?** When used appropriately and not too frequently, joint injections are generally safe and effective. Overuse of corticosteroids can have negative effects on cartilage, so modern protocols often incorporate regenerative therapies. **Does my horse have to retire if it has arthritis?** Many horses with degenerative joint disease continue to work comfortably at reduced levels with proper management. Some remain in full work depending on the joints affected and severity. This information is for educational purposes only. Always consult with a licensed veterinarian for diagnosis and treatment of your horse. Signs include: Progressive lameness that worsens with work; joint swelling or effusion; reduced range of motion and stiffness, especially after rest; pain on flexion of the affected joint; shortened stride and reluctance to perform certain movements; muscle atrophy around the affected limb in chronic cases; bony enlargement around the joint in advanced osteoarthritis
The carpus is commonly injured in racehorses. Chip and slab fractures are treated arthroscopically.
See the Third Carpal Bone (Right) on our interactive 3D horse model. Open 3D Model