The elbow joint consists of the humerus, radius, and ulna. It is a ginglymus (hinge) joint supported by medial and lateral collateral ligaments. Elbow lameness is uncommon in horses; however, it should be considered if the source of pain cannot be isolated to the distal limb.
Of the injuries that can occur to the elbow in horses, the most common is fracture of the olecranon. Olecranon fracture has a characteristic dropped-elbow, flexed-carpus, non-weight-bearing lameness; other causes of elbow pain are more difficult to identify. Careful examination that includes manipulation (flexion, extension, and rotation) is essential.
Synoviocentesis achieved via lateral approaches either near the collateral ligament or into the caudal pouch, followed by local anesthetic injection, is the best method of diagnosing elbow lameness in a horse. Radiography is limited to mediolateral (limb extended) and craniocaudal (weight-bearing) projections. Ultrasonography enables inspection of the lateral joint margins and lateral collateral ligament, as well as the medial collateral ligament. Physiological imaging methods such as scintigraphy and thermography can show changes consistent with pathology.
Developmental Orthopedic Disease of the Elbow in Horses
Subchondral defects and subchondral cystlike lesions (SCLs) in horses occur most commonly in the proximal medial radius and the distal medial humeral condyle (see cystlike lesion image). Like cysts in other locations, these lesions usually occur in young horses and are treated with the typical regimens of rest, intra-articular medication, and controlled exercise.
Courtesy of Dr. Tracy A. Turner.
Arthroscopic surgery in these locations is difficult because of limited access; however, the distal humeral condyles can be visualized arthroscopically. Proximal radial lesions cannot be adequately accessed arthroscopically. These lesions need to be approached extra-articularly. The prognosis is considered fair to good with conservative therapy if there is no evidence of osteoarthritis. Surgery is recommended if conservative therapy fails to decrease lameness after 90 days.
Other types of developmental orthopedic disease in the elbow joint, which occur commonly in other species, are rare or unrecognized in horses.
Fractures of the Elbow in Horses
The most commonly encountered fracture of the equine elbow affects the olecranon of the ulna (see olecranon fracture image).
Courtesy of Dr. Tracy A. Turner.
Ulnar fractures occur most commonly in horses < 2 years old, but they can occur at any age. They usually result from external trauma; in foals, however, they can result from excessive tensile load on the triceps. Ulnar fractures are divided into six types depending on configuration and comminution (see ulnar fracture image). Many olecranon fractures displace under the influence of the triceps muscle and require tension-band internal fixation.
Courtesy of Dr. Tracy A. Turner.
Diagnosis of elbow fracture is based on posture of the horse, palpation, and radiography. Radiography is necessary to identify the fracture configuration; a minimum of two views (medial to lateral and cranial to caudal) are required. Nondisplaced, nonarticular ulnar fractures are candidates for conservative therapy consisting of complete stall rest for 8 weeks, with or without splinting to keep the carpus straight. However, the best method of treatment is tension-band internal fixation.
In foals, fracture repair must be monitored carefully because implants can interfere with limb growth (the proximal radial physis fuses at 11–24 months of age), and implants should be removed as soon as satisfactory healing has been achieved.
Two unusual variations of ulnar fracture in horses are marked avulsion of the ulnar epiphysis and elbow luxation. Salter-Harris Type I or II fractures of the ulnar physis (which fuses at 24–36 months of age) can retract the epiphysis so far proximally that it is inapparent on a standard mediolateral radiograph and can be missed. Elbow luxation secondary to ulnar fracture must be treated surgically with internal fixation.
The prognosis for horses with ulnar fractures is good when treated appropriately. Articular fractures require particular attention for accurate surgical reconstruction of the joint.
Stress fractures at the craniodistal humeral metaphysis, just above the elbow, can also occur in racehorses. The history is often similar to that for fractures of the proximal humerus and other stress fractures. Mediolateral radiographs often reveal periosteal and endosteal reaction at the predilection site. These periosteal changes can often also be detected with ultrasonography. Scintigraphy is a more sensitive method than radiography to detect these fractures.
Management of distal humeral stress fractures is tailored to the horse's comfort and severity of the initial injury. As is the case for other injuries of this type, it consists of a careful return to exercise, balancing structural integrity with biomechanical requirements for healing.
Osteoarthritis of the Elbow in Horses
Degenerative joint disease (osteoarthritis) of the elbow joint in horses, in the absence of an inciting primary lesion, is managed as described for the shoulder and other joints. Some horses present with lameness localized to the elbow joint by diagnostic anesthesia but with few or inconclusive abnormalities evident via radiography and ultrasonography. Subchondral bone damage could be the source of pain in these cases.
Collateral Ligament Injury of the Elbow in Horses
Elbow collateral desmitis has been reported for both lateral and medial ligaments in horses. Radiography can reveal new bone (enthesiophytes) associated with collateral ligament injury. Many cases are diagnosed via scintigraphy, with an area of increased radiopharmaceutical uptake at the origin or insertion of collateral ligaments. Ultrasonography is the best imaging modality to evaluate these ligaments. The lateral collateral is easier to evaluate; however, both should be assessed.
The prognosis in cases of collateral ligament injuries depends on their severity. Currently, no proven therapies exist to augment ligament healing. Various treatments have been tried, including intra-articular medication, periligamentous injection of biologics (eg, platelet-rich plasma), and extracorporeal shock wave therapy.
Olecranon Bursitis in Horses
Olecranon bursitis (commonly called shoe boil or capped elbow) occurs at the point of the elbow and is characterized by an accumulation of bursal fluid and thickening of the bursal wall with fibrous tissue. In horses, it usually develops as a nonpainful swelling that does not typically interfere with locomotion unless it becomes greatly enlarged. This is a cosmetic injury unless it becomes infected.
Infection of the bursa is painful, causes lameness, and can break open and drain. Olecranon bursitis is thought to be caused by the shoe hitting the point of the elbow when the horse lies down. Radiography and ultrasonography are used to evaluate the bony and soft tissues associated with the lesion.
Treatment is to eliminate the cause of bursitis, generally by applying a padded collar (called a "donut") to the pastern to prevent direct contact of the shoe with the skin over the elbow; it should be initiated as soon as the problem is noted. Providing extra bedding and/or switching to nonabrasive bedding (eg, avoiding sawdust) is also indicated.
Fluid in the bursa can be removed aseptically; however, the bursa usually refills with fluid over time. Surgical placement of drains with bandaging, along with rest for 8 weeks, can be successful; chronic or infected olecranon bursitis, however, is difficult to treat.
Key Points
Olecranon fracture is fairly common in horses and generally carries a good prognosis with internal fixation.
Distal humeral stress fractures can occur in the elbow region of Thoroughbred racehorses.
Subchondral cystic lesions can occur in the distal humerus or proximal radius.
Osteoarthritis and collateral ligament injury of the elbow are relatively uncommon in horses but do occur.
For More Information
Garvican E, Clegg P. Clinical aspects of the equine shoulder and elbow joints. Companion Anim. 2008;13(5):5-12.
Ashton N. Partial avulsion of the ulnaris lateralis and enthesiopathy of the lateral epicondyle of the humerus in a thoroughbred race horse. Ir Vet J. 2018;71:10.
Also see pet owner content regarding disorders of the shoulder and elbow in horses.
