Articulatio carpi
The carpus (commonly called the knee) is the joint between the radius and the cannon bone. It consists of two rows of small carpal bones (typically 7–8 bones total, including the accessory carpal bone) and three main joint levels: radiocarpal (antebrachiocarpal), middle carpal (intercarpal), and carpometacarpal. Most movement occurs at the radiocarpal and middle carpal joints. The carpus flexes and extends to absorb concussion and allow the lower limb to clear the ground during the swing phase. Because of the high forces at speed, the dorsal aspects of the carpal bones are common sites of osteochondral chip fractures and slab fractures, especially in racehorses. The accessory carpal bone provides leverage for the flexor muscles and can also fracture from trauma.
Origin: N/A (bone)
Insertion: N/A (bone)
Action: Absorbs concussion during locomotion; allows flexion and extension of the lower forelimb, mainly at the radiocarpal and middle carpal joints
Chip (osteochondral) fractures are most common on the distal radial carpal bone, proximal third carpal bone, and distal intermediate carpal bone. Slab fractures most often involve the third carpal bone (frontal plane). Both are treated arthroscopically when possible. Synovitis, osteoarthritis, and ligament injuries also occur. Skyline radiographs are essential for evaluating the third carpal bone.
## Overview A slab fracture of the third carpal bone extends through the full thickness of the bone from one joint surface to another. It is more serious than a chip fracture and is common in Thoroug
## Overview Carpal arthritis, or carpitis, is inflammation and degenerative joint disease of one or more carpal joints. It is common in racehorses and sport horses that experience repetitive high-spe
## Overview Carpal chip fractures are osteochondral fragments that break from the dorsal margins of the carpal bones, most often during high-speed exercise. They are a leading cause of lameness in ra
Sudden lameness with a swollen knee after fast work or a race should be examined promptly; radiographs and often arthroscopy are needed. Chronic swelling or reduced flexion may indicate arthritis or previous chip damage. Proper shoeing and gradual conditioning help reduce risk.
## Overview A slab fracture of the third carpal bone extends through the full thickness of the bone from one joint surface to another. It is more serious than a chip fracture and is common in Thoroughbred racehorses. Acute lameness during fast work, marked carpal effusion, and a severe flexion response are typical. Surgical lag-screw repair is the treatment of choice. ## Causes High-speed loading. ## Diagnosis Radiographs. Computed tomography may be needed for full assessment. ## Treatment Lag-screw fixation under arthroscopic guidance for slabs thicker than about 10 mm. Thin fragments may be removed. ## Recovery and Prognosis Fair to good with accurate repair. Osteoarthritis can develop. ## Prevention Training management in racehorses. Signs include: acute lameness during racing or fast work; marked carpal effusion; severe flexion test; radiographic slab fracture
## Overview Carpal arthritis, or carpitis, is inflammation and degenerative joint disease of one or more carpal joints. It is common in racehorses and sport horses that experience repetitive high-speed loading or hyperextension of the knee. Synovitis, cartilage damage, and eventual osteoarthritis produce lameness and reduced performance. ## Causes Repetitive concussion, hyperextension, chip fractures, and conformational faults that unevenly load the carpus are the main drivers. Acute trauma can also initiate the process. ## Diagnosis Forelimb lameness that worsens with carpal flexion, joint effusion, and reduced range of motion are typical. Radiographs show osteophytes, joint-space narrowing, or sclerosis. Diagnostic analgesia confirms the carpus as the source of pain. ## Treatment Rest, anti-inflammatory medication, intra-articular corticosteroids or biologics, and corrective shoeing are standard. Arthroscopic removal of fragments or debridement is indicated when chips or cartilage flaps are present. Workload modification is essential for long-term management. ## Recovery and Prognosis Mild synovitis often resolves with appropriate rest and treatment. Established osteoarthritis is progressive; many horses remain useful with management, but high-level athletic careers may be shortened. ## Prevention Gradual conditioning, good footing, and early treatment of chip fractures reduce progression to advanced arthritis. Signs include: forelimb lameness; carpal joint effusion; pain on flexion; reduced range of motion; positive response to carpal flexion test
## Overview Carpal chip fractures are osteochondral fragments that break from the dorsal margins of the carpal bones, most often during high-speed exercise. They are a leading cause of lameness in racehorses. Common locations include the distal radial carpal bone and proximal third carpal bone. Fragments cause synovitis and, if left untreated, progressive cartilage damage. ## Causes Hyperextension and repetitive loading of the carpus during fast work are the primary mechanisms. Poor conformation, fatigue, and unsuitable racing surfaces contribute. ## Diagnosis Joint effusion, lameness that improves with carpal flexion or worsens after work, and positive response to intra-articular analgesia are typical. Radiographs demonstrate the fragment. Arthroscopy provides definitive assessment of cartilage damage. ## Treatment Arthroscopic removal of the fragment is the treatment of choice. Postoperative rest and progressive rehabilitation follow. Prognosis depends on the degree of cartilage injury observed at surgery. ## Recovery and Prognosis Many horses return to racing after uncomplicated chip removal. Extensive cartilage loss lowers the chance of sustained high-level performance. ## Prevention Gradual introduction to high-speed work and attention to track surface may reduce incidence, although evidence is limited. Signs include: carpal joint effusion; forelimb lameness after fast work; pain on carpal flexion; radiographic osteochondral fragment
Chip (osteochondral) fractures are most common on the distal radial carpal bone, proximal third carpal bone, and distal intermediate carpal bone. Slab fractures most often involve the third carpal bone (frontal plane). Both are treated arthroscopically when possible. Synovitis, osteoarthritis, and ligament injuries also occur. Skyline radiographs are essential for evaluating the third carpal bone.
Sudden lameness with a swollen knee after fast work or a race should be examined promptly; radiographs and often arthroscopy are needed. Chronic swelling or reduced flexion may indicate arthritis or previous chip damage. Proper shoeing and gradual conditioning help reduce risk.
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