Locking Stifles- upper fixation of the patella

upper fixation of the patella is not a Friesian specific issue, but we talk about everything and it's come up a lot. People have tried to say that Frisians are more prone to it because they have such flexible tendons.... but they also say Friesians foals are prone to lax tendons and prone to hyper flexed tendons. In all the years of having Friesians I have only had 1 horse get upper fixation of the patella, she was in a small area for an extended period of quarantine time while in a critical growth phase. Once we could exercise her she was symptom free and had no issues in years to come. We have also never had a foal with contracted or lax tendons, so don't feel that it's only a Friesian thing.

What is upper fixation of the patella

The patella in a horse is also called the stifle. This part is located on the front of the hind leg at the top just before it gets to the main body. If you feel it on the horse it will feel a lot like a human knee cap, it's very similar. Horses have a locking or stay apparatus built into their stifle so that they can effortlessly sleep standing up. So it is very natural for any and all horses regardless of breed or age to "lock" their patella. The problems are when this happens in exercise or does not release normally.  There are various severities, from a slight catching as they stride, to locking before they stride out and have to "step it out" to needing human assistance to unlock it.



Causes for locking stifles
- Lack of fitness and exercise - get those horses out, trot them over poles, up and down hills, do transition work.
- Longer than normal distal patellar ligaments - these can be tightened with exercise, but it should also be pointed out that growing phases can affect tendon lengths.
- Strait or upright pelvic limb conformation - not normally in Friesians, more seen in halter quarter horses, but it's important to breed for good leg angles.

- Negative plantar angle - seen on the back feet where the coffin bone is tipping upward and the heel is dropped. This directly affects the function of the stifle joint. So make sure your hoofs get proper trimming, x ray if needed. Like in humans if the feet are off or shoes are off it will affect everything up to your hips, spine and neck. No hoof, no horse.


If you horse exhibits any locking, trot to canter resistance, lameness that doesn't respond to anti-inflammatories, drag their toes, difficulties backing and with hills, lameness when coming out of stall rest that gets better with moving. Or if they have outright visible locking of the stifle, please have them checked out.  

The most effective way to treat/prevent this situation is to have a horse that is conformational correct, in regular exercise and able to move regularly.

Other more significant treatments if the horse is chronic include corrective shoes (to fix the coffin bone angle). Also estrogen therapy has been known to help as well as ligament injections. In sever cases it can be addressed surgically to restrict locking.

I do not have a video of this as the horse was in quarantine when she was affected. But if you search on Youtube.com for "locking stifle" you will see many videos showing affected horses. If you have a youtube video link that you would like me to use for this blog feel free to send it to me, but please leave it online indefinitely so that I do not post a dead link.