The issue of chips forming in equine joints is becoming increasingly common. Here, we discuss the nature of this condition, its causes, and appropriate supplementation practices. Osteochondrosis dissecans (OCD), the advanced form of osteochondrosis characterized by the presence of bone and cartilage fragments, is commonly referred to as "joint mice" or "chips." This condition develops due to disturbances in endochondral ossification.

When the tissues at the junction of bone and articular cartilage do not receive proper nutrition, it leads to ischemic necrosis of chondrocytes. This results in local thickening of the articular cartilage and the separation of a bone-cartilage fragment in the area where chondrocytes have died.

Factors Contributing to OCD ("Chips"):

·     Genetic predisposition

·     Rapid growth

·     Improper nutrition

·     Foal rearing system

·     Injuries

While no direct genetic cause of OCD has been definitively proven, studies suggest that a high inbreeding coefficient in breeding may increase the risk of developing the condition. Inadequate diets, especially those based on high-energy feeds, can promote excessive muscle growth, which disrupts the balance between the skeletal system and muscle mass. Excessive weight and rapid height gain at the withers can lead to osteochondrosis dissecans due to increased joint overload.

The balance of macro- and microelements in the diet is also crucial. An excessive calcium-to-phosphorus ratio and copper deficiencies contribute to the development of osteochondrosis.

Foal rearing systems and birth season also play a role. Studies show a significantly lower incidence of OCD in foals with unrestricted pasture access before and after weaning. Foals born in winter have less opportunity for free movement compared to those born in spring and early summer.

A stall-based rearing system (with only 4–5 hours of pasture time per day) is not optimal for proper foal development and increases the risk of OCD. Limited movement during the growth phase impairs circulation, leading to insufficient nutrition of the tissues between bone and cartilage. This ultimately results in cartilage necrosis and, eventually, OCD.

Prognosis for OCD

The prognosis for osteochondrosis dissecans varies and depends on factors such as the horse’s age, chip size, and its location within the joint.

There are three stages of osteochondrosis, classified based on severity:

1.   Osteochondrosis latens (latent stage)

2.   Osteochondrosis manifesta (subclinical stage)

3.   Osteochondrosis dissecans (separating stage)

To find the right supplementation tailored to your horse's needs, consult our nutritional advisor: dietary consultation.