Os carpi radiale (Cr)
The radial carpal bone is the most medial bone of the proximal row of the carpus. It is the largest of the proximal carpal bones and articulates proximally with the radius, distally with the second and third carpal bones, and laterally with the intermediate carpal bone. Because of its position and the forces transmitted through the carpus during high-speed exercise, the dorsal aspect of the radial carpal bone is a common site of chip fractures in racehorses.
Chip fractures of the radial carpal bone are a frequent cause of carpal lameness in racehorses. Diagnosis is radiographic; arthroscopic removal is the standard treatment for many chip fractures and generally carries a good prognosis for return to work when addressed promptly. Joint effusion and positive response to flexion or intra-articular anesthesia help localize the problem.
## Overview Osteochondral chip fractures are among the most frequent causes of lameness in Thoroughbred and Standardbred racehorses. They predominantly affect the dorsal aspects of the carpal joints
## 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
## Overview Slab fractures extend from one articular surface completely through the bone to another articular surface. In the carpus they are most often frontal slabs of the third carpal bone in race
## 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 and appropriate management improve outcomes for chip fractures.
## Overview Osteochondral chip fractures are among the most frequent causes of lameness in Thoroughbred and Standardbred racehorses. They predominantly affect the dorsal aspects of the carpal joints and the proximal sesamoid bones or distal cannon bone at the fetlock. Repetitive high-speed loading is the dominant risk factor. ## Causes Fatigue-related microdamage that propagates under the extreme loads of racing and training. ## Diagnosis Same as for chip fractures in general: effusion, lameness, radiographs, and arthroscopic evaluation. ## Treatment Prompt arthroscopic removal followed by controlled rehabilitation gives the best chance of return to racing. ## Recovery and Prognosis Return-to-racing rates are good for uncomplicated chips but decline with increasing cartilage damage or multiple fragments. ## Prevention Training modifications and surface management are under investigation; no single preventive measure is proven. Signs include: carpal or fetlock effusion; lameness after fast work; positive flexion tests; radiographic chips
## 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
## Overview Slab fractures extend from one articular surface completely through the bone to another articular surface. In the carpus they are most often frontal slabs of the third carpal bone in racehorses. They cause acute lameness and joint effusion and require surgical repair. ## Causes High-energy loading. ## Diagnosis Radiographs. ## Treatment Lag-screw fixation. ## Recovery and Prognosis Fair to good with accurate reduction. ## Prevention Monitoring of racehorses. Signs include: acute lameness; joint effusion; radiographic slab extending through the bone
## 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
Chip fractures of the radial carpal bone are a frequent cause of carpal lameness in racehorses. Diagnosis is radiographic; arthroscopic removal is the standard treatment for many chip fractures and generally carries a good prognosis for return to work when addressed promptly. Joint effusion and positive response to flexion or intra-articular anesthesia help localize the problem.
Acute carpal swelling or lameness after fast work should be evaluated promptly. Early diagnosis and appropriate management improve outcomes for chip fractures.
See the Radial Carpal Bone (Left) on our interactive 3D horse model. Open 3D Model