Locking stifles/patella

[ImogenBurrows]

Hi
I have recently purchased a 5 yr old halfbred who, it is becoming apparent, has hindlimb issues! As a vet (albeit not an equine one) I think he has patellar luxation; seems to "lock" on upward canter transition, then strike off disunited, also drags toes. He was vetted sound for sale so no comebacks there. Would like to event him eventually if possible. Are intra-articular injections the best treatment option, how frequently are they administered, and would treatment be ongoing, or sporadic? I am based in ROI and know a few good horse vets so i wouldn`t be administering it myself!! thanks.

Patellar luxation is pretty rare in anything other than mini breeds so IME it'd be unlikely to be that, but possible.

If he is dragging the leg when the stifle "locks" then this is likely to be another condition known as upward fixation of the patella, or "locking stifles". The horse can stand without using energy, with the leg fixed using a nifty set up of muscles, tendons and ligaments known collectively as the passive stay apparatus. The medial (inside) patella ligament hooks over a bump of bone on the bottom of the femur and locks into a fix position. Then when the horse shifts to rest the weight bearing leg, the patellar is moved upwards by the muscles and this allows the ligament to unhook so to speak.

This condition is particularly common in young horses, or those which happen to be poorly muscled for one reason or another. In early cases or those with infrequent locking episodes, I generally advise increasing the exercise levels to build these muscles up.

Next step if it persists, is to do a medial patellar ligament desmotomy, cutting the ligament which allows the locking action. This has little side effect other than the horse has to expend energy when resting a leg

A this is not an intra-articular problem, intra-articular joint medication will not be of any use in these cases. It also can shock the horse and rarely they panic (which usually unhooks the leg anyway!) but in it's own right it is a non-painful condition - but more one of mechanics. Once released the horse will be totally sound again.

Hope that helps.
Imogen

 

[roscommon2]

Thankyou very much for the information, just to check, what work up would be appropriate (i.e. radiography/other imaging) and would the desmotomy acheive the best result? I already heard my equine vet discussing "filling up the joint" presumably not the best approach. Would the surgery be done in a hospital under GA generally speaking? thanks a lot.

 

[ImogenBurrows]

Thankyou very much for the information, just to check, what work up would be appropriate (i.e. radiography/other imaging) and would the desmotomy acheive the best result? I already heard my equine vet discussing "filling up the joint" presumably not the best approach. Would the surgery be done in a hospital under GA generally speaking? thanks a lot.

No problem

We diagnose generally based on clinical signs and history...it's usual that we'll have seen the horse locking up at some point.

As a rule we encourage survey xrays on one or ideally both stifles to rule out underlying issues, but as there is no lameness or joint involvement blocking/distending the joint is of no use.

Routinely the surgery is actually done under sedation and local. It's very straightforward to do and the anatomy is in the easiest position to assess when standing. This also has the advantage the horse comes in for xrays, has op and goes home. Needs box rest until stitches/staples come out in 14d, then back into work

Not so bad. And much cheaper and less risky than a GA.

Imogen