Jumping is a very strenuous activity that places high physical demands on the horse. The primary stresses affect the suspensory apparatuses of the hind legs during take-off and the forelegs during landing, though the galloping and turning associated with jumping also place torque on the joints. Most injuries, chronic or acute, begin with strain; as structures in the horse’s body absorb the shock of take-off and landing, they acquire small amounts of damage. Over time, this damage leads to inflammation of the tendons (tendinitis) and ligaments (desmitis). The most common injuries in the forelimb occur to the interosseous ligaments and the superficial digital flexor tendons and less commonly, the accessory ligament of the deep digital flexor tendon. Strain on the superficial digital flexors is greater when jumping higher fences, so horses may no longer be suitable for competitive jumping after damaging that apparatus.
The effects of jumping on the hind legs can include injuries to the proximal, medial, or lateral branches of the suspensory ligaments. Jumping horses can also be at a higher risk of developing osteochondritis dissecans (OCD) or other arthritic conditions, even at a young age. Genetic and environmental components play roles in the development of OCD in horses: some families have weaker joints, but excessive growth over a short period of time, age-inappropriate exercise regimens and nutrition can also contribute. Jumping performance is especially influenced by the presence of arthropathic hocks. One study found that at breeding stock evaluations, horses with radiographically diagnosed athropathies of the hock joints scored significantly lower than their healthy peers for the quality of the canter, jumping technique, and ability and their character. The pain associated with arthropathic conditions likely makes the horses unwilling to push powerfully off their hindlegs, a quality necessary for jumping and cantering and which could make the horse appear lazy or unwilling to work.
Indications of lameness in jumping horses typically come in the form of a change in habits: sudden or developing reluctance to turn, land on a certain lead, or “add” a stride and jump “deep”; difficulties altering the stride length or making the distances in a combination; and developing habits like rushing, stopping and refusing, or frequent lead changes.[4] Unfortunately, many of these undesirable habits can also be the result of poor training, which challenges riders and owners to identify the causes of bad behavior.