Osteochondrosis of the Stifle in Horses

This component of developmental orthopedic disease (DOD), as noted above, can affect horses in any breed and any gender, generally as foals or young horses. It sometimes will present with mild signs of lameness early in the life of a foal but can also not really be noted until the horse is a yearling and attention is shifted to yearling sales and training begins, generally between the ages of 2 and 4 years. It affects the joint cartilage and the subchondral bone in the stifle of the horse which is usually exhibited as joint effusion (swelling) as the normal fluid contained in the joint is increased.

Osteochondrosis in horses is a sign of developmental orthopedic disease (DOD) in a young horse of virtually any breed. It can be a composite of growth, diet, and genetics.

The most common symptoms that you will note in your horse if this condition is possibly present will be swelling in the joint area. This swelling can be noted in several joints which include:

• Hocks
• Stifle
• Fetlock

The swelling associated with osteochondrosis can be present as early in life as 5 months of age but most often occurs or shows up with the horse begins to work or train. The lameness caused by the swelling around and in the joint usually isn’t noted when the horse is walking but, rather, will be exacerbated when the gait speeds are increased or when the equine is put through work routines.

Types 

Developmental orthopedic disease (DOD) in horses is the umbrella under which osteochondrosis falls. This is but one manifestation or type of DOD and some of the other related types are:

• Osteochondritis dissecans which can affect 5 to 25 percent of horses in any breed
• Angular limb deformities 
• Bone cysts
• Bone malformation (crushed carpal and tarsal bones)
• Wobbler syndrome
• Flexural limb deformity

While these types may have similar factors which increase the risk of development, the physiopathology (the functional changes accompanying syndromes and diseases) is not the same for each of them.

Osteochondrosis is typified by a failure of normal endochondral ossification, one of two biological processes occurring in all mammals by which bone tissue is born, which, in this case, is occurring in the limbs of the equine as it grows into adulthood. The tissue that is in question in osteochondrosis is the joint cartilage and it’s abnormalities include thickness, softening, collapse or total separation from the supporting bone (called osteochondritis dissecans or OCD). Here are some of the other causes of osteochondrosis:

• Genetics - Can be affected by presence of environmental risks, either high or low (higher risks for foals whose sires were affected, decreased copper, calcium and phosphorus in diet increases risk factor)
• Nutrition - Overfeeding to gain maximum growth potential increases risk of development of osteochondrosis (decreased copper, calcium and phosphorus in diet increases risk factors)
• Exercise - Increased risk in foals who are stall-rested and do not participate in regular periods of exercise
• Conformation - Relates to genetics and overfeeding for optimal growth
• Some biomechanical forces
• Trauma
• Stress response
• In utero environment
• Hormonal reactions

As always, if your equine presents with severe lameness or severe joint swelling, it is vital to have him evaluated by your veterinary professional on an emergent basis. If there is a problem, it will need to be addressed as soon as possible to avoid permanent injury. You veterinarian will first do a physical examination and a lameness evaluation of your equine, then, based on what he finds on physical and lameness exams, he will likely need to enlist the aid of several imaging techniques to arrive at his diagnosis:

• Radiographs (x-rays) to ascertain the presence of any lesions or abnormalities in the stifle area
• Ultrasound imaging will likely be used to image any soft tissue anomalies which may be present. 

After these imaging techniques have provided their insight, your veterinarian will put together the total package which will include his findings, taking into consideration the location, severity, the age of the horse, the clinical signs, the duration of the disease and the expectations of the owner. He will then develop an appropriate treatment plan.

The treatment plan recommended by your veterinarian will, of course, depend on the results of the diagnostic portion of the evaluation. But it will likely consist of combination of rest, dietary changes, non-steroidal anti-inflammatory medications, intra-articular (arthritic) medications, and oral joint supplements. These treatments will likely be used for those young horses having mild disease. But for those equines having more severe diagnoses, surgical options may be recommended which will include arthroscopic removal of fragments or abnormal tissue or lesions. This option would likely be advantageous for those wishing to offer the horse for sale since the presence of an osteochondrotic lesion would most likely reduce the expected sale price. It is important to note, if horse shows are your expectation for your horse, that chronic swelling of the joint may not necessarily be eliminated with surgical options. Treatment options which also might not do well are noted below:

• Stifle lesions as compared to hock and fetlock lesions
• Large lesions
• Lesions having osteochondral fragmentation

Depending on the severity and location of the osteochondrosis, after the initial onset episode has been treated, you can expect a period of time in which your horse will likely be confined to stall rest. This will likely be followed by a progressive exercise routine with return to full work and training likely to take months to achieve. Wrapping or bandaging of the limb may be required postoperatively for a specific period of time. Medications for postop inflammation may be prescribed but beyond this, more specific recommendations will come from your veterinary surgeon based upon the extent and type of surgery done. The prognosis of your horse should be relatively good, again, dependent upon the severity of the lesion and extent of any damage done to the subchondral bone.