OCD, by definition, refers to a disturbance of cellular differentiation in the growing cartilage. OCD can manifest itself in two syndromes – dissecting lesions of the cartilage (flaps or loose bodies with resulting articular defects) or as sub-chrondal bone cysts. As it affects joint structure and function, OCD is a performance limiting condition and there are questions as to preventability. Incidence of OCD is worldwide and is increasing. International studies suggest that as many as 10-25% of horses are affected.
o many factors are involved
- defect in cartilage maturation (OCD and subchondral bone cysts)
- cartilage and bone defects combined with inflammatory products impair joint function
o hereditary/genetic predisposition,
o growth rate and body size
o endocrinology (hormonal)
o biomechanics /exercise / trauma
- imbalance in calcium / phosphorus ratio or amount
- imbalance in other minerals and vitamins
- copper deficiency
- excess energy and / or crude protein
This can be difficult as all joints can be affected – stifle, hock, shoulder (difficult to treat ),fetlock (common in foals ), knee, elbow, pastern, coffin bone, hip and cervical joints. The success of diagnosis depends on the joint(s) involved. Diagnosis is confirmed by radiology and arthroscopic examination, after a physical examination.
Foals usually show clinical signs when under 6 months of age- more lying down, joint swelling and stiffness, difficulty keeping up with their dams and paddock mates.
In yearlings and adult horses, OCD presents variations in degree of lameness (slightly to severely lame). Lesions can, in some horses, be present without lameness being shown; other horses show an asymmetric or awkward gait. Lameness can be more consistent on response to joint flexion.
Management of the various syndromes of OCD involves deciding between conservative treatment and surgical intervention, restriction of exercise and a decrease in food intake and the use of anti-inflammatory drugs to slow down the inflammatory process.
Surgical intervention depends on the site and severity of the lesions and usually involves arthroscopy.
Balanced nutrition and a steady growth rate. Avoid excessive energy and crude protein intake in feeding program and ensure correct dietary copper status. Most important, avoid breeding from genetic carriers (genetic predisposition has been suggested in the horse but is not well defined). In one study in horses, many of the cases could be related back to two sires. Genetic factors could operate directly or indirectly by influencing growth rate.