Fetlock Joint
Articulatio metacarpophalangea
Overview
The fetlock joint (metacarpophalangeal or metatarsophalangeal joint) is formed by the cannon bone (MC3/MT3), the proximal phalanx (P1), and the two proximal sesamoid bones on the palmar/plantar aspect. It is analogous to a human knuckle. During galloping the joint hyperextends dramatically: the fetlock can drop nearly to the ground, acting as a major shock absorber and energy-storage mechanism. Support comes from the suspensory apparatus (suspensory ligament, proximal sesamoid bones, and distal sesamoidean ligaments) plus the flexor tendons. The joint allows flexion, extension, and controlled hyperextension. It is the most commonly injured joint in the athletic horse. Soft-tissue injuries (suspensory ligament branches, flexor tendons) and fractures of the sesamoid bones or proximal phalanx are frequent. Catastrophic breakdown of the suspensory apparatus (biaxial sesamoid fractures or complete ligament rupture) is the leading cause of fatal musculoskeletal injury in racehorses.
Anatomical Details
Origin: N/A (bone)
Insertion: N/A (bone)
Action: Major shock absorber; allows flexion, extension, and hyperextension during locomotion; supported by the suspensory apparatus
Clinical Significance
Imaging includes radiography, ultrasonography, and MRI. Suspensory apparatus failure produces a dropped fetlock and non-weight-bearing lameness. Many injuries have pre-existing lesions. Prognosis ranges from good for minor soft-tissue injuries to grave for complete suspensory apparatus disruption.
Common Conditions & Injuries
Fetlock arthritis / synovitis
## Overview Fetlock arthritis and synovitis are inflammation and degenerative change of the metacarpophalangeal or metatarsophalangeal joint. Joint effusion (windpuffs), shortened stride, and positiv
Proximal sesamoid bone fracture
## Overview Fractures of the proximal sesamoid bones range from small apical or basilar chips to catastrophic biaxial fractures in which both sesamoids break and the fetlock collapses. Chip fractures
Sesamoiditis
## Overview Sesamoiditis is chronic inflammation and remodeling of the proximal sesamoid bones from repetitive loading and suspensory ligament traction. It is common in young racehorses and sport hor
What Horse Owners Should Know
Heat, swelling, or lameness localized to the fetlock needs veterinary evaluation. Sudden severe lameness with a dropped fetlock after high-speed work is an emergency; stabilize the limb if possible and call the veterinarian immediately. Do not force the horse to walk.
Frequently Asked Questions
What is Fetlock arthritis / synovitis in horses?
## Overview Fetlock arthritis and synovitis are inflammation and degenerative change of the metacarpophalangeal or metatarsophalangeal joint. Joint effusion (windpuffs), shortened stride, and positive flexion tests are common. It is frequent in performance horses and often bilateral. ## Causes Repetitive loading, osteochondral injury, or primary osteoarthritis. ## Diagnosis Lameness examination, flexion tests, diagnostic analgesia, radiographs, and ultrasound. ## Treatment Intra-articular medications, systemic anti-inflammatories, rest, and workload modification. Management is ongoing. ## Recovery and Prognosis Fair to good for comfort with treatment. Advanced osteoarthritis limits athletic use. ## Prevention Sensible training schedules and early treatment of joint inflammation. Signs include: joint effusion (windpuffs); shortened stride; lameness worse after work; positive flexion test; often bilateral
What is Proximal sesamoid bone fracture in horses?
## Overview Fractures of the proximal sesamoid bones range from small apical or basilar chips to catastrophic biaxial fractures in which both sesamoids break and the fetlock collapses. Chip fractures cause lameness and effusion and are often removed arthroscopically. Biaxial fractures are usually fatal on the racetrack. ## Causes Hyperextension injury during high-speed work. ## Diagnosis Radiographs. The clinical appearance of a dropped fetlock indicates severe disruption. ## Treatment Arthroscopic removal for chips. Surgical repair or euthanasia for more severe fractures depending on configuration. Biaxial fractures are almost always fatal. ## Recovery and Prognosis Good for small chips. Poor to grave for comminuted or biaxial fractures. ## Prevention Monitoring for early suspensory or sesamoid changes in racehorses. Signs include: lameness and fetlock effusion with chips; catastrophic biaxial fracture causes the fetlock to drop to the ground
What is Sesamoiditis in horses?
## Overview Sesamoiditis is chronic inflammation and remodeling of the proximal sesamoid bones from repetitive loading and suspensory ligament traction. It is common in young racehorses and sport horses. Signs include low-grade forelimb lameness, pain on palpation of the sesamoids, a positive flexion test, and enlarged, remodeled sesamoids on radiographs. ## Causes Repetitive strain at the suspensory insertion. ## Diagnosis Radiographs showing sesamoid changes, correlated with clinical signs. Ultrasound or scintigraphy may add information. ## Treatment Rest, anti-inflammatories, and gradual return to work. Shock wave or regenerative therapies are sometimes used. Prognosis for high-level performance is often guarded. ## Recovery and Prognosis Guarded for return to previous athletic level in many cases. ## Prevention Careful training of young horses and early management of suspensory soreness. Signs include: chronic low-grade forelimb lameness; pain on sesamoid palpation; positive flexion test; enlarged remodeled sesamoids on radiographs
What are the clinical concerns for the Fetlock Joint?
Imaging includes radiography, ultrasonography, and MRI. Suspensory apparatus failure produces a dropped fetlock and non-weight-bearing lameness. Many injuries have pre-existing lesions. Prognosis ranges from good for minor soft-tissue injuries to grave for complete suspensory apparatus disruption.
What should horse owners know about the Fetlock Joint?
Heat, swelling, or lameness localized to the fetlock needs veterinary evaluation. Sudden severe lameness with a dropped fetlock after high-speed work is an emergency; stabilize the limb if possible and call the veterinarian immediately. Do not force the horse to walk.
Explore This Structure in 3D
See the Fetlock Joint on our interactive 3D horse model. Open 3D Model