Phalanx proximalis et media
The proximal phalanx (long pastern, P1) and middle phalanx (short pastern, P2) form the pastern region. P1 extends from the fetlock joint to the pastern joint; P2 extends from the pastern joint to the coffin joint. The pastern joint (proximal interphalangeal or PIP joint) between P1 and P2 is a lower-motion joint that contributes to shock absorption and allows limited flexion and extension. The superficial digital flexor tendon inserts near this joint, and the deep digital flexor tendon passes behind it. P1 is one of the most commonly fractured bones in racehorses, particularly sagittal fractures. The angle of the pastern affects concussion absorption; a more upright pastern transmits more force upward.
Origin: N/A (bone)
Insertion: N/A (bone)
Action: Shock absorption; allows limited flexion between the fetlock and hoof; the angle of the pastern affects concussion absorption - a more upright pastern transmits more concussion
Ringbone (osteoarthritis of the pastern joint) is a common condition that can cause progressive lameness. P1 fractures are significant injuries in racehorses. Disease of the pastern joint can alter limb biomechanics and indirectly affect loading of the foot and navicular region. Diagnosis uses clinical examination, nerve blocks, and radiographs; advanced imaging is sometimes needed.
## Overview Fracture of the proximal phalanx (P1, long pastern bone) is one of the most common long-bone fractures in racehorses. It is often sagittal (splitting the bone lengthwise) or comminuted an
## Overview Fracture of the middle phalanx (P2, short pastern bone) is less common than P1 fracture but serious because both the pastern and coffin joints are often involved. Acute lameness, pastern
Ringbone is a form of osteoarthritis that affects the pastern joint (high ringbone) or coffin joint (low ringbone). It involves the formation of new bone around the joint margins and can be articular
Shortened stride, heat or swelling over the pastern, or reluctance to work on hard ground should be evaluated. Correct hoof balance and appropriate shoeing help manage many pastern issues.
## Overview Fracture of the proximal phalanx (P1, long pastern bone) is one of the most common long-bone fractures in racehorses. It is often sagittal (splitting the bone lengthwise) or comminuted and frequently occurs during racing or fast work. Acute lameness, pastern swelling, and pain are typical. Displaced fractures are non-weight-bearing. Surgical screw fixation is the usual treatment for sagittal fractures. ## Causes High-speed loading, often propagating from a pre-existing stress lesion. ## Diagnosis Radiographs, including multiple oblique views. ## Treatment Lag-screw fixation for sagittal fractures. Comminuted fractures have a poorer prognosis and may require more complex repair or euthanasia in severe cases. ## Recovery and Prognosis Good for simple sagittal fractures with accurate repair. Guarded to poor for highly comminuted fractures. ## Prevention Monitoring for early stress changes in racehorses. Signs include: acute lameness during exercise; swelling over the pastern; pain on palpation; non-weight-bearing if displaced; radiographic fracture
## Overview Fracture of the middle phalanx (P2, short pastern bone) is less common than P1 fracture but serious because both the pastern and coffin joints are often involved. Acute lameness, pastern swelling, and pain on manipulation are typical. Comminuted fractures carry a poor prognosis. ## Causes Trauma or high-energy loading. ## Diagnosis Radiographs of the pastern. ## Treatment Surgical repair with screws or plates when possible. Severe comminution may not be repairable. ## Recovery and Prognosis Fair for simple fractures. Poor for highly comminuted articular fractures. ## Prevention Trauma avoidance. Signs include: acute lameness; swelling of the pastern; pain on manipulation; radiographic fracture; poor prognosis if comminuted
Ringbone is a form of osteoarthritis that affects the pastern joint (high ringbone) or coffin joint (low ringbone). It involves the formation of new bone around the joint margins and can be articular (involving the joint surface) or periarticular (new bone formation around the joint without direct surface involvement). The condition causes progressive lameness and is more common in the front feet. ## What it is Ringbone develops when there is damage to the joint cartilage and supporting structures, leading to inflammation, cartilage loss, and the formation of osteophytes (bone spurs). In high ringbone, the pastern joint is primarily affected. In low ringbone, changes occur around the [coffin joint](/anatomy/coffin-bone-distal-phalanx-p3). Articular ringbone involves the joint surface itself and generally carries a more guarded prognosis than periarticular forms. Over time, the joint may fuse (ankylose), which can eventually reduce pain but limits motion. ## Signs and symptoms - Progressive lameness that worsens with work, especially on hard ground - Firm, bony swelling around the pastern - Shortened stride and reduced fetlock or pastern flexion - Pain on flexion of the affected joint - In advanced cases, visible bony enlargement around the pastern - Reluctance to land heel-first or turn tightly ## Causes and risk factors Ringbone is often secondary to repetitive stress, conformational faults (especially upright pasterns or long toes), previous joint trauma, or developmental issues. Horses in high-impact disciplines and those with poor hoof balance are at increased risk. Low ringbone is frequently associated with chronic [laminitis](/conditions/laminitis) or other coffin joint pathology. ## How it is diagnosed Diagnosis is based on clinical signs, palpation, and radiographs. X-rays typically show new bone formation around the joint margins, joint space narrowing, and in advanced cases, ankylosis. Diagnostic analgesia helps confirm the joint as the source of pain. In some cases, MRI provides additional detail about cartilage and soft tissue involvement. ## Treatment and management Treatment focuses on reducing pain and slowing progression. Options include corrective farriery to improve breakover and support the joint, systemic anti-inflammatories, and intra-articular injections (corticosteroids, hyaluronic acid, or regenerative therapies). In advanced cases where the joint has fused or pain is severe, surgical arthrodesis may be considered for the pastern joint. Long-term management often includes ongoing farriery and controlled exercise. ## When to call the vet Contact your veterinarian if your horse develops progressive lameness, bony swelling around the pastern, or reduced joint flexibility. Early intervention can help slow the progression of ringbone and improve long-term comfort. ## Prevention Prevention centers on maintaining good hoof balance, avoiding excessive stress on young or developing joints, and prompt treatment of any joint injuries. Regular farriery and appropriate conditioning programs help reduce risk, especially in horses with conformational predispositions. ## Frequently asked questions **What is the difference between high and low ringbone?** High ringbone affects the pastern joint (between P1 and P2). Low ringbone affects the coffin joint (between P2 and P3). **Can ringbone be cured?** No. It is a progressive condition. Treatment aims to manage pain and slow progression. In some cases the joint eventually fuses, which can reduce pain. **Is my horse still rideable with ringbone?** Many horses remain rideable at reduced levels with proper management. Advanced cases may be limited to light work or pasture soundness. 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, especially on hard ground; firm, bony swelling around the pastern; shortened stride and reduced fetlock or pastern flexion; pain on flexion of the affected joint; in advanced cases, visible bony enlargement around the pastern; reluctance to land heel-first or turn tightly
Ringbone (osteoarthritis of the pastern joint) is a common condition that can cause progressive lameness. P1 fractures are significant injuries in racehorses. Disease of the pastern joint can alter limb biomechanics and indirectly affect loading of the foot and navicular region. Diagnosis uses clinical examination, nerve blocks, and radiographs; advanced imaging is sometimes needed.
Shortened stride, heat or swelling over the pastern, or reluctance to work on hard ground should be evaluated. Correct hoof balance and appropriate shoeing help manage many pastern issues.
See the Pastern Bones (P1 and P2) on our interactive 3D horse model. Open 3D Model