Horse Side Vet Guide ®

Equine Health Resource

Medial Patellar Ligament Desmotomy



Medial patellar ligament desmotomy (MPD), is a surgical procedure that is performed to correct the upward fixation of the patella (UFP), also known as a “locking” patella. Historically, it was the treatment of choice for UFP. However, MPD is now considered a last resort due to its detrimental side effects. It is only recommended in severe cases of complete locking, or in cases that are unresponsive to conservative management (conditioning and/or splitting) or other other treatment options.

There is almost no reason for this procedure to be used today because of the excellent results reported using patellar ligament splitting, and without the side effects.


The procedure is done standing. The horse is sedated and skin at the area of the incision is anesthetized with local anesthetic. A vertical incision several centimeters long is made over the ligament. A sharp, curved surgical instrument is passed under the ligament and the ligament is cut. The skin incision is sutured.

By cutting the medial patellar ligament completely, the patella no longer catches on the medial trochlear ridge of the femur, and so the stifle no longer locks.

Postoperative monitoring includes stall rest with gradually increasing hand walking over a 90 day period, then conditioning for work may begin. If successful, the locking of the patella should stop, and there should only be mild swelling and no drainage or increase in lameness.


Your vet should be aware of other methods of treating this condition, including medial patellar ligament splitting.


You should know that this procedure has been replaced by a superior procedure without as many side effects, medial patellar ligament splitting or fenestration.

Related DiagnosesThis Treatment Might Be Used for these Diagnoses

Consider Potential Side Effects & Complications

Loss of the medial patellar ligament changes the mechanics of the joint, and can result in long term damage to the patella. Other potential side effects are joint infection, incision breakdown (dehiscence), and failure to correct the problem.

Consider Reasons Not To Use This Treatment

Due to the side effects and complications, this surgery is a last alternative.

Is It working? Timeframe for effect

Immediate resolution of the problem.

Questions To Ask My Vet

  • Can you tell me more about the other treatment options?
  • Why do you recommend this treatment over others?
Author: Doug Thal DVM Dipl. ABVP


Peitzmeir MD, Koontz ZD, Lynch TM, et al. Outcome of medial patellar ligament desmoplasty for treatment of intermittent upward fixation of the patella in 24 horses (2005 - 2012). Canadian Vet J 2015: 56(2): 193-5.


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