Os carpale III (C3)
The third carpal bone (C3) is the largest of the distal row of the carpus. It articulates proximally with the radial and intermediate carpal bones and distally with the third metacarpal (cannon) bone. Because of its position and the forces transmitted through the carpus during high-speed exercise, it is the most common site of slab fractures in racehorses.
Slab fractures of the third carpal bone are a common cause of carpal lameness in racehorses. Diagnosis is radiographic. Treatment is often surgical (arthroscopic removal or internal fixation depending on configuration). Prognosis depends on the fracture configuration and degree of articular damage.
## Overview Slab fractures are very common in racehorses, particularly frontal slabs of the radial facet of the third carpal bone. They occur during high-speed exercise and produce acute carpal lamen
## Overview Incomplete or stress fractures are cracks that do not fully break the bone. They result from repetitive loading before the bone has adapted. They are common in racehorses and cause lamene
## Overview Subchondral bone sclerosis is increased density of the bone beneath the joint cartilage from repetitive loading. It is a response to stress and can precede more serious injury such as fra
## Overview Degenerative joint disease, also called osteoarthritis, is the progressive loss of articular cartilage accompanied by changes in the underlying bone and joint capsule. It is one of the mo
Acute carpal swelling or lameness after fast work should be evaluated promptly. Early diagnosis improves outcomes.
## Overview Slab fractures are very common in racehorses, particularly frontal slabs of the radial facet of the third carpal bone. They occur during high-speed exercise and produce acute carpal lameness and effusion. Surgical repair with lag screws is standard. ## Causes Repetitive high-speed loading. ## Diagnosis Radiographs, sometimes with computed tomography. ## Treatment Arthroscopically guided lag-screw fixation. ## Recovery and Prognosis Many horses return to racing after successful repair. ## Prevention Training adjustments when early carpal changes are detected. Signs include: acute carpal lameness during fast work; effusion; radiographic slab of the third carpal bone
## Overview Incomplete or stress fractures are cracks that do not fully break the bone. They result from repetitive loading before the bone has adapted. They are common in racehorses and cause lameness that may be subtle. If training continues they can propagate to complete fracture. ## Causes Cyclical fatigue of bone. ## Diagnosis Clinical examination, radiographs, and scintigraphy for early lesions. ## Treatment Rest until radiographic healing. Modification of the training schedule on return. ## Recovery and Prognosis Good if rested before complete fracture occurs. ## Prevention Gradual introduction of high-speed work. Signs include: lameness after fast work; focal pain; radiographic stress fracture line; risk of progression if training continues
## Overview Subchondral bone sclerosis is increased density of the bone beneath the joint cartilage from repetitive loading. It is a response to stress and can precede more serious injury such as fracture or osteoarthritis. It is seen on radiographs or computed tomography in performance horses, especially racehorses. ## Causes Repetitive high-load exercise. ## Diagnosis Imaging showing increased bone density. ## Treatment Modification of training to allow bone remodeling. Rest if associated with lameness. ## Recovery and Prognosis Good if workload is adjusted before catastrophic injury. ## Prevention Appropriate training progression. Signs include: often subclinical; may contribute to lameness; increased bone density on imaging; seen in high-level performance horses
## Overview Degenerative joint disease, also called osteoarthritis, is the progressive loss of articular cartilage accompanied by changes in the underlying bone and joint capsule. It is one of the most common causes of chronic lameness in horses and can affect any joint, though certain joints (hock, coffin, fetlock, stifle) are frequently involved in performance horses. ## Causes Repetitive loading, prior trauma, conformational faults, or developmental joint disease. Inflammation and mechanical stress drive the progression. ## Diagnosis Lameness examination, flexion tests, diagnostic analgesia, and imaging (radiographs show osteophytes and joint-space changes; advanced imaging assesses cartilage). ## Treatment Intra-articular medications (corticosteroids, biologics, viscosupplements), systemic anti-inflammatories, shoeing or trimming adjustments, and workload modification. Management rather than cure is the goal. ## Recovery and Prognosis Many horses remain comfortable and useful for years with appropriate management. Advanced disease eventually limits athletic career length. ## Prevention Early treatment of joint inflammation, balanced shoeing, and sensible training programs. Signs include: progressive lameness worse with work; joint effusion; stiffness after rest; reduced range of motion; muscle atrophy in chronic cases
Slab fractures of the third carpal bone are a common cause of carpal lameness in racehorses. Diagnosis is radiographic. Treatment is often surgical (arthroscopic removal or internal fixation depending on configuration). Prognosis depends on the fracture configuration and degree of articular damage.
Acute carpal swelling or lameness after fast work should be evaluated promptly. Early diagnosis improves outcomes.
See the Third Carpal Bone (Left) on our interactive 3D horse model. Open 3D Model