ANGULAR limb deformities (ALD) are a group of common conditions affecting the conformation of horse limbs. They are either present from birth or develop in the first few weeks and months of life. They are caused by disturbances in the ‘growth plates’ of the leg bones.

A growth plate is a sliver of cartilage present close to the bone ends in young animals (figure 1). The cells in the cartilage divide as the animal grows and are then replaced by new bone cells, allowing the bone to get longer. Once the bone has reached its adult length new cartilage stops being produced and the plate fills in with bone tissue and eventually disappears.