Phalanx proximalis (P1)
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.
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 Sagittal fractures split a bone lengthwise in the sagittal plane. In horses they most often affect the proximal phalanx in racehorses. They cause acute lameness and are diagnosed on radio
## Overview Osteochondral fragmentation is the formation of small bone-and-cartilage chips at joint margins, most often from hyperextension injury in racehorses (carpus, fetlock) or as part of osteoc
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 Sagittal fractures split a bone lengthwise in the sagittal plane. In horses they most often affect the proximal phalanx in racehorses. They cause acute lameness and are diagnosed on radiographs. Screw fixation is the standard treatment for complete sagittal fractures. ## Causes High-speed loading, often propagating from a stress lesion. ## Diagnosis Radiographs. ## Treatment Lag-screw fixation. ## Recovery and Prognosis Good for simple sagittal fractures with accurate repair. ## Prevention Monitoring for early stress changes. Signs include: acute lameness; radiographic sagittal fracture line; common in the proximal phalanx of racehorses
## Overview Osteochondral fragmentation is the formation of small bone-and-cartilage chips at joint margins, most often from hyperextension injury in racehorses (carpus, fetlock) or as part of osteochondritis dissecans. Fragments cause joint inflammation and lameness. Arthroscopic removal is the standard treatment for clinically significant chips. ## Causes Acute overload or developmental failure of ossification. ## Diagnosis Radiographs. Arthroscopy confirms and treats. ## Treatment Arthroscopic removal. Prognosis is good for uncomplicated chips. ## Recovery and Prognosis Good. ## Prevention Training management and early treatment of joint inflammation. Signs include: joint effusion; lameness; radiographic chip fragment at a joint margin
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 Proximal Phalanx / Long Pastern Bone (Left Hindlimb) on our interactive 3D horse model. Open 3D Model