Hello,

Discussing this question withJan Glas resulted in the following comment:

Problems with the stifle are not uncommon as it is one of the biggest joints in the horse. So if a horse presents with a stifle problem there could be many explanations like congenital malformation, defective development , trauma, infection , degenerative disease and vascular disturbances (rare).

Locking stifle or in veterinary surgery terms “upward fixation of the patella” is seen in Friesian horses and Shetlanders more often than most other breeds.

First of all you want to make sure the diagnosis is correct. For example a loose piece of cartilage in osteochondritis dissecans (OCD) can put a lock on a stifle as well ( so you need an x-ray to sort this out) . Other causes mimicking an upward fixation of the patella can be : sprains of collateral ligaments, injury to cruciate ligaments, injury to menisci and less frequent are fractures.

Upward fixation of the patella is influenced by some hereditary factors , by the build of the stifle , how the muscular development is and how the horse is standing on its hooves

In acute upward fixation of the patella, the hindquarter is locked in extension as the horse attempts to pull the limb forward. You will observe a typical situation : fetlock, pastern and coffin are flexed while stifle and hock joints are locked in extension. In late chronic or repeated cases there can be signs of gonitis or inflammation of the joint. Often the condition is seen bilateral. Advancing the limb the horse will be seen to drag his toe ending in excessive toewear on the front of the hoof. In many cases it is not so obvious : a horse can be  locked, standing in its box and can get loose again by stepping outside.

So first of all you need to be sure of the diagnosis for this dictates  the type of treatment .   In an acute fixation you might want to back the horse, and push at the same time the patella medially and downward. On the other hand  if it is a young horse with lack of muscle development or a fast growing horse in one of its periods of disbalance between bone, joint and muscular development, then you might get away with training on straight stretches with as less turning as possible. Training by pulling a sledge can be combined with straight work. Try to give the horse as much movement as possible by turning  out as much as possible .

You might check with your farrier: inside/ medial  taking out of the hooves , forcing the hoof to be lower on the inside / medial side  than on the outside/ lateral side and even making hoofs as short as possible can be beneficial.

Surgery is an option, but only if all other treatment gives no results.

In Shetlanders with chronic upward fixation surgery in terms of  “medial patellar desmotomy” is carried out. In Friesian horses you might wait with surgery until severe complaints. After surgery a broodmare can still be used for breeding with the restriction that there is a possibility of transmitting this problem to offspring. A horse for the carriage might have less visible signs after surgery than a horse in dressage.

Regards  Jan Glas and Harry Voesten

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