The problem of OCD – osteochondrosis dissecans

It has been shown that 25 % of the European warmblood and thoroughbred population suffer from osteochondrosis dissecans (OCD), a non-inflammatory, degenerative disease of bone and cartilage tissue, from a young age. It is not uncommon for OCD to render a young horse unfit for sport, and surgery is often even necessary. In addition to factors such as husbandry, genetics, growth rate, sex and biochemical stressors, diet also plays a role in the development of OCD.

What is OCD?
Terms such as ‘chip’, ‘sequester’, ‘dissected fragment’, ‘joint mouse’, ‘joint body’, ‘isolated shadow’ or even ‘joint stone’ are often encountered in the literature or during pre-purchase examinations. All these synonyms describe the same clinical condition: osteochondrosis dissecans (OCD). OCD is a developmental joint disorder in which bone-cartilage fragments (osteochondral fragments) detach from the bone, thereby forming what are known as loose bodies. These free osteochondral bodies can, as the condition progresses, lead to functional impairment of the joint and damage to the surrounding tissue (cartilage, tendons), which may manifest clinically as pain, lameness and reduced performance. The condition mainly affects the weight-bearing joints of the limbs; in particular, the hock joint, followed by the fetlock and knee joints.

What is OCD?
Osteochondrosis dissecans (osteo = bone, chondro = cartilage) is a degenerative condition affecting bone and cartilage tissue. More specifically, it is a non-inflammatory change affecting the articular cartilage and the subchondral bone tissue. Radiographic studies have shown that 25 % of the European warmblood and thoroughbred population are affected by OCD. The foundations for the development of OCD are laid as early as foalhood, as OCD is a multifactorial disorder of bone growth. This means that several factors may be involved in the development of this developmental skeletal disorder. Factors such as husbandry and biomechanical stress stimuli influence the development of the growing musculoskeletal system. In addition, factors such as genetic predisposition, growth rate, genetically determined final height, as well as dietary factors (e.g. over- or under-nutrition), hormonal imbalances and metabolic disorders (often resulting from a diet-related imbalance) play a decisive role in the development of OCD. Factors such as sex and month of birth also appear to play a role. For instance, the fetlock joint is said to be affected more frequently in filly foals, whilst the hock joint is more commonly affected in colt foals. Various studies have also shown that foals born before 1 April develop OCD at a strikingly higher rate.

What role does age play?
A horse’s growth in size takes place mainly during the first few months of life. At birth, the foal has already reached 60–65 % of its final size. By the time it is a yearling, this figure is already around 90 %, and by the age of three, 98 % of its final size. Growth is always associated with specific nutritional requirements, which is why uncontrolled growth spurts can lead to nutritional deficiencies. If there is a lack of appropriate structural and functional nutrients during these key growth phases, the development of a stable musculoskeletal system may be impaired. OCD is one of the possible consequences.

What does prevention involve?
Experts agree that a genetic predisposition undoubtedly plays a part in the development of OCD, but that rearing practices play a crucial role in both its development and prevention.

This is where feeding comes into play!
Whilst high quantities of cereals, due to their high glycaemic response, promote the development of OCD, an appropriate intake of functional nutrients can counteract the development of OCD. These functional nutrients include, amongst others, glycosaminoglycans, which have a high water-binding capacity and thus support the shock-absorbing properties of joint cartilage. In addition, nucleotides and β-glucans promote the healthy synthesis of bone and cartilage tissue. Other functional nutrients, such as chondroitin sulphate, collagen peptides and low-molecular-weight peptides, contribute to the optimal development of the musculoskeletal system.