The carpus of horses comprises three articulations: the radiocarpal (antebrachiocarpal), intercarpal (middle carpal), and carpometacarpal joints. Problems are localized to the carpal region on the basis of lameness, swelling, synovial effusion, pain on flexion, and diagnostic analgesia.
Visualization and palpation are important to determine the site of swelling in the carpus (eg, synovial fluid in the joint versus synovial fluid in the tendon sheath versus swelling in the subcutaneous space). Knowledge of the normal anatomical boundaries of the structures is important to identify fluid location.
Diagnostic analgesia of the carpus is usually administered intra-articularly. The antebrachiocarpal and middle carpal joints can be injected easily. The carpometacarpal joint communicates with the middle carpal joint; therefore, local analgesia in the middle carpal joint provides analgesia of the carpometacarpal joint. There is considerable distal palmar outpouching of the carpometacarpal joint; with time, analgesia will diffuse into the area of the proximal suspensory ligament, potentially creating diagnostic confusion.
Radiography of the carpus is critical for specific diagnoses and should include flexed lateral and skyline views of the distal row of carpal bones (as well as of the proximal row/distal radius in some horses).
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Also see pet owner content regarding disorders of the carpus and metacarpus in horses.
