Signalment & History
- This patient presents for left pelvic limb lameness.
- On physical examination, his vitals are normal. There is a Grade 2 lameness in the left pelvic limb at a trot and a Grade 4 lameness in the same limb centered at the stifle joint after the joint flexion test. The remaining lameness examination is normal.
Findings
There is a mild increase in soft tissue opacity within the stifle joint. There is a well-defined, irregularly marginated concave defect along the cranioproximal aspect of the lateral femoral trochlear ridge, associated with moderate subchondral sclerosis. Two, well-defined, sharply marginated mineral fragments are seen along the cranial aspect of the lateral femoral trochlear concave defect. The tibial tuberosity apophysis closes at approximately 30-36 months of age. This is a normal finding in a 24 month old horse.
Diagnosis
- This patient is diagnosed with osteochondritis dissecans of the lateral trochlear ridge of the distal left femur with associated mild joint effusion.
Conclusions
Osteochondritis dissecans in horses
- OCD refers to a disturbance of cellular differentiation in the growing cartilage
- It is pathologically manifested as dissecting lesions of the cartilage which result in flaps or loose bodies with resulting articular defects
- OCD is often bilateral and radiographs of the opposite joint should be taken
- Commonly affected joints:
- Femoropatellar joint – commonly affect the lateral trochlear ridge
- Tarsocrural joint – commonly affect the cranial aspect of the intermediate ridge of the distal articular surface of the tibia
- Shoulder joint
- Metacarpophalangeal joint
- OCD is multifactorial and not yet defined; may be due to:
- Rapid growth and large body size
- Nutritional: High energy diets, low copper diets, excessive zinc intakes
- Genetics: may be partially inherited
- Hormonal imbalances: insulin and thyroid hormaones
- Bone necrosis secondary to trauma
- Sometimes older horses are diagnosed with OCD incidentally without apparent clinical signs.
References
- ACVS.org
- Jacquet S, Robert C, Walette JP, Denoix JM. Evolution of radiological findings detected in the limbs of 321 young horses between the ages of 6 and 18 months. Vet J. 2013;197(1):58-64.
- Turner S. Diseases of Bones and Related Structures. In: Stashak TS. Adam’s Lameness in Horses, 4th Ed. Lea & Febiger; Philadelphia; 1987:293-485
