Scapula
The scapula (shoulder blade) is a large, flat, roughly triangular bone that lies against the thoracic wall. It does not form a true bony joint with the trunk but is attached solely by muscles (synsarcosis or the thoracic sling). The spine of the scapula runs along its lateral surface and divides it into the supraspinous and infraspinous fossae. The glenoid cavity at the distal end articulates with the humerus to form the shoulder joint. In the horse the scapula is oriented cranioventrally and is critical for forelimb extension and weight bearing. The angle of the scapula affects stride length. The scapular cartilage is a crescent-shaped cartilaginous extension at the dorsal border of the scapula. It enlarges the area for muscle attachment and acts as a shock absorber during locomotion. The cartilage gradually ossifies with age, becoming more brittle and less effective as a shock absorber in older horses.
Scapular fractures are uncommon but serious. The thoracic sling is critical for suspending the thorax between the forelimbs. Scapular cartilage ossification is a normal age-related change. Relevant in evaluations of shoulder function and after trauma.
## Overview Scapular fractures are uncommon and usually result from direct trauma. The supraglenoid tubercle is the most frequent site. Horses present with acute severe forelimb lameness and variable
## Overview Osteochondrosis of the shoulder is a developmental lesion, most often of the humeral head or glenoid cavity. It is less common than hock or stifle OCD but causes more significant lameness
## Overview Ossification of the scapular cartilage is an age-related mineralization of the cartilage along the top of the shoulder blade. It is usually an incidental radiographic finding in older hor
Injury to the suprascapular nerve as it crosses the cranial border of the scapula, typically from direct trauma (collision with doorframes, trees). Causes denervation atrophy of the supraspinatus and
Sudden severe lameness or swelling over the shoulder after trauma should be evaluated immediately. Correct saddle fit helps protect the region.
## Overview Scapular fractures are uncommon and usually result from direct trauma. The supraglenoid tubercle is the most frequent site. Horses present with acute severe forelimb lameness and variable shoulder swelling. Treatment ranges from conservative management to internal fixation depending on the configuration. ## Causes Direct trauma (kicks, falls, collisions). ## Diagnosis Radiographs of the shoulder. Scintigraphy or computed tomography may be needed. Intra-articular analgesia helps localize pain. ## Treatment Many body or neck fractures are managed with rest. Supraglenoid tubercle fractures may benefit from surgical removal or fixation in selected cases. Prognosis varies. ## Recovery and Prognosis Fair to guarded depending on fracture type and articular involvement. ## Prevention Trauma avoidance. Signs include: acute severe forelimb lameness; shoulder swelling; shortened cranial stride; radiographic scapular fracture
## Overview Osteochondrosis of the shoulder is a developmental lesion, most often of the humeral head or glenoid cavity. It is less common than hock or stifle OCD but causes more significant lameness. Young horses show forelimb lameness and sometimes shoulder-muscle atrophy. Arthroscopic treatment is possible but technically demanding, and the prognosis is more guarded than for other joints. ## Causes Failure of normal cartilage ossification. ## Diagnosis Radiographs of the shoulder, sometimes with contrast or advanced imaging. ## Treatment Arthroscopic debridement when feasible. Conservative management for some lesions. Athletic prognosis is guarded. ## Recovery and Prognosis Guarded compared with hock or stifle OCD. ## Prevention Growth and nutrition management. Signs include: forelimb lameness in a young horse; shoulder muscle atrophy in chronic cases; radiographic osteochondrosis of the humeral head or glenoid
## Overview Ossification of the scapular cartilage is an age-related mineralization of the cartilage along the top of the shoulder blade. It is usually an incidental radiographic finding in older horses and rarely causes clinical signs. ## Causes Aging. ## Diagnosis Radiographs showing mineralization in a horse without shoulder pain. ## Treatment None if asymptomatic. ## Recovery and Prognosis Not applicable. ## Prevention None. Signs include: radiographic mineralization of the scapular cartilage; usually incidental in older horses
Injury to the suprascapular nerve as it crosses the cranial border of the scapula, typically from direct trauma (collision with doorframes, trees). Causes denervation atrophy of the supraspinatus and infraspinatus muscles. Signs include: Characteristic lateral shoulder instability ('shoulder slip') during weight bearing; rapid atrophy of supraspinatus and infraspinatus creating a visible hollow above the scapular spine; lateral subluxation of the shoulder during weight bearing; Rapid dramatic wasting of the muscles on either side of the scapular spine; the scapular spine becomes extremely prominent; shoulder instability; the shoulder may pop laterally during weight bearing; often from running into a solid object.; Obvious muscle wasting below the scapular spine; shoulder visibly slips laterally during walking; angular shoulder appearance; often recovers spontaneously over months if nerve not severed.
Scapular fractures are uncommon but serious. The thoracic sling is critical for suspending the thorax between the forelimbs. Scapular cartilage ossification is a normal age-related change. Relevant in evaluations of shoulder function and after trauma.
Sudden severe lameness or swelling over the shoulder after trauma should be evaluated immediately. Correct saddle fit helps protect the region.
See the Scapula (Right) on our interactive 3D horse model. Open 3D Model