MSD Manual

Please confirm that you are a health care professional

honeypot link

Developmental Diseases of the Shoulder in Horses

By

Marcus J. Head

, BVetMed, Rossdales Equine Hospital and Diagnostic Centre

Last full review/revision Sep 2015 | Content last modified Oct 2015

Developmental orthopedic disease manifests in the scapulohumeral (shoulder) joint principally as subchondral cyst-like lesions (bone cysts) affecting the glenoid of the scapula or as osteochondritis dissecans of the humeral head. Also, a condition almost exclusive to miniature ponies, caused by dysplasia of the joint and attributable to hypoplasia of the joint surfaces, results in instability and secondary arthritis.

Subchondral Cyst-like Lesions:

Bone cysts may develop in the glenoid, or socket, of the shoulder joint. They may or may not communicate with the shoulder joint and respond variably to intra-articular anesthesia. Although part of the developmental orthopedic disease complex, signs may not be apparent until the animal is mature. In common with other manifestations of this syndrome, lameness may not become a feature until the animal begins work (typically breaking in or early ridden exercise). Occasionally, bone cysts may be a cause of lameness in an older horse, having remained quiescent for most of the animal’s life; the reason for these later onset cases is not clear.

Diagnosis is made by localization with intra-articular anesthesia, by exclusion of lower limb disease, or occasionally by gamma scintigraphy. Radiographs should document the lesion, although some cysts are too small to be seen.

Treatment in young horses consists of rest in the hope the cyst will remodel to become nonpainful; however, this happens only rarely. Intra-articular medication can provide relief from lameness but usually only transiently. Some disease-modifying preparations show promise (eg, autologous conditioned serum), and some clinicians favor the use of systemic glycosaminoglycans. Surgical debridement is difficult in most cases, because the cyst location and articular cartilage damage that causes secondary osteoathritis may limit its effectiveness; however, it can be very successful. Injection of corticosteroids directly into the cyst via an extra-articular approach could be appropriate, but the lack of 3-dimensional imaging of this region in horses makes the approach hard to plan.

Osteochondritis Dissecans:

Derangement of cartilage and bone development on the humeral head can result in weakness within the articular cartilage that may lead to erosion or formation of a free flap of cartilage. Typically, the caudal part of the head is affected, or at least it is the part most evident on radiographs. In other joints, osteochondritis dissecans often can be treated successfully with arthroscopic debridement. Unfortunately, access to the shoulder joint is severely restricted, and in most cases the full extent of the lesion cannot be seen or treated. Clinical resolution in all but the mildest cases in young horses is rare. Rest and various medications have been tried, with little documented success.

Scapulohumeral Dysplasia:

Seemingly unique to the miniature breeds, this condition arises from a mismatch between the size of the glenoid and humeral head. This causes instability of the joint and secondary arthritis. Although undoubtedly a developmental problem, probably with a significant degree of heritability, many cases do not present until the animal is an adult, and the history is often of sudden onset lameness. On physical examination, proximal limb muscle atrophy is often profound and lameness considerable. These factors, along with the breed disposition and the often-present sign of resentment of proximal limb manipulation, make localization straightforward. Radiographs reveal the presence of osteoarthritis and variable subluxation of the scapulohumeral articulation. Oblique views may demonstrate deep erosion of the humeral head in severe cases. The generalized destruction of the joint produces a “hot spot” on a bone scan, if performed. There is no simple treatment. Most cases present at such an advanced stage that even palliative care is impossible; euthanasia on humane grounds should be considered in such situations. Surgical arthrodesis has been described but is rarely performed.

OTHER TOPICS IN THIS CHAPTER

Lameness in Horses
Overview of Lameness in Horses
The Lameness Examination in Horses
Imaging Techniques in Equine Lameness
Arthroscopy in Equine Lameness
Regional Anesthesia in Equine Lameness
Disorders of the Foot in Horses
Osseous Cyst-like Lesions in the Distal Phalanx in Horses
Bruised Sole and Corns in Horses
Canker in Horses
Fracture of Navicular Bone in Horses
Fracture of Distal Phalanx in Horses
Keratoma in Horses
Laminitis in Horses
Navicular Disease in Horses
Pedal Osteitis in Horses
Puncture Wounds of the Foot in Horses
Pyramidal Disease in Horses
Quittor in Horses
Quarter Crack in Horses
Scratches in Horses
White Line Disease in Horses
Sheared Heels in Horses
Sidebone in Horses
Thrush in Horses
Disorders of the Pastern and Fetlock
Fractures of the First and Second Phalanx in Horses
Fractures of the Proximal Sesamoid Bones in Horses
Osteoarthritis of the Proximal Interphalangeal Joint in Horses
Palmar/Plantar Metacarpal/Metatarsal Nonadaptive Bone Remodeling in Horses
Sesamoiditis in Horses
Chronic Proliferative Synovitis in Horses
Digital Sheath Tenosynovitis in Horses
Disorders of the Metacarpus in Horses
Tendinitis in Horses
Suspensory Desmitis in Horses
Inferior Check Desmitis in Horses
Bucked Shins in Horses
Exostoses of the Second and Fourth Metacarpal Bones in Horses
Fractures of the Small Metacarpal (Splint) Bones in Horses
Fracture of the Third Metacarpal (Cannon) Bone in Horses
Disorders of the Carpus in Horses
Fracture of the Carpal Bones in Horses
Subchondral Bone Disease of the Third Carpal Bone in Horses
Tearing of the Medial Palmar Intercarpal Ligament in Horses
Osteoarthritis of the Carpus in Horses
Distal Radial Exostosis and Osteochondroma of the Distal Radius in Horses
Carpal Hygroma in Horses
Rupture of the Common Digital Extensor Tendon in Horses
Disorders of the Shoulder in Horses
Developmental Diseases of the Shoulder in Horses
Fractures of the Shoulder in Horses
Bicipital Bursitis in Horses
Infection of the Shoulder in Horses
Suprascapular Neuropathy in Horses
Osteoarthritis of the Shoulder in Horses
Disorders of the Elbow in Horses
Developmental Orthopedic Disease in the Elbow of Horses
Fractures of the Elbow in Horses
Osteoarthritis of the Elbow in Horses
Collateral Ligament Injury in the Elbow of Horses
Disorders of the Metatarsus in Horses
Bucked Shins/Dorsal Cortical Fractures of the Third Metatarsal Bone in Horses
Exostoses of the Metatarsal Bones in Horses
Diaphyseal Fracture of the Third Metatarsal Bone in Horses
Incomplete Longitudinal Fractures of the Plantar Aspect of the Third Metatarsal Bone in Horses
Focal Bone Reaction and Avulsion Fractures of the Third Metatarsal Bone in Horses
Fractures of the Second and Fourth Metatarsal Bones in Horses
Enostosis-like Lesions of the Third Metatarsal Bone in Horses
Disorders of the Tarsus in Horses
Failure of Ossification of the Distal Tarsal Bones in Horses
Osteoarthritis of the Distal Tarsal Joints in Horses
Osteoarthritis of the Talocalcaneal Joint in Horses
Osteoarthritis of the Tarsocrural Joint in Horses
Synovitis/Capsulitis of the Tarsocrural Joint in Horses
Osteochondrosis of the Tarsocrural Joint in Horses
Osteitis of the Calcaneus in Horses
Fractures of the Distal Tarsal Bones in Horses
Fracture of the Talus in Horses
Fracture of the Fibular Tarsal Bone (Calcaneus) in Horses
Fracture of the Lateral Malleolus of the Tibia in Horses
Tarsal Joint Luxation in Horses
Desmitis of the Collateral Ligaments of the Tarsus in Horses
Rupture of the Fibularis (Peroneus) Tertius in Horses
Stringhalt
Curb in Horses
Disorders of the Tarsal Sheath in Horses
False Thoroughpin in Horses
Luxation of the Superficial Digital Flexor Tendon from the Tuber Calcanei in Horses
Gastrocnemius Tendinitis in Horses
Calcaneal Bursitis in Horses
Capped Hock
Disorders of the Stifle in Horses
Osteochondrosis of the Stifle in Horses
Subchondral Cystic Lesions in Horses
Meniscus and Meniscal Ligament Injuries in Horses
Cranial and Caudal Cruciate Ligament Injuries in Horses
Collateral Ligament Injuries in Horses
Intermittent Upward Fixation of the Patella and Delayed Patella Release in Horses
Fragmentation of the Patella in Horses
Patellar Luxation in Horses
Others also read
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Test your knowledge

Musculoskeletal Disorders in Large Animals
A seven-year-old Quarter horse gelding presents with a 1-week history of mild lameness. During the examination, the horse raises his head as he places weight on his left forelimb and drops it when placing weight on the right forelimb. Which limb is most likely affected in this horse?
Become a Pro at using our website 

Also of Interest

Become a Pro at using our website 
TOP