In a research paper presented at the 2014 AAEP Convention, three researchers described a surgical procedure called “medial patellar ligament splitting” that was performed on 64 horses with a delayed patellar release. This condition is not uncommon and occurs when the ligament that connects the patella (the knee cap) to the tibia (the long bone that runs from the stifle down to the hock) gets “hooked” on a rounded structure of the end of the femur (medial trochlear ridge) as the horse extends the entire hind limb. The limb is then “locked” into an extended position for a varying length of time until the horse can hyperflex the leg or back up and release the ligament/patella and return the leg to normal function. The delayed patellar release is a bit subtler than upward fixation of the patella (“locking stifles”) and “often occurs as the horse moves from a standing still position or during a downward transition.”
These horses may not “lock up” entirely and may show less obvious signs of the problem. This research paper evaluated a surgical procedure in which a small scalpel blade is used to make very small stab incisions along the medial patellar ligament, with the idea being to create scar tissue that will thicken the ligament and cause it to release more easily. The medical records of 64 horses that had this procedure were evaluated, and follow-up information was obtained via telephone calls to the owners and/or clinical evaluation by a veterinarian. The results showed that 89% of these horses benefitted from this procedure, with 58% having complete resolution and 31% showing improvement. 73% of the horses were able to perform at the owner’s desired level following the procedure. 63% of horses showed improvement within 30-60 days after the procedure. The researchers also noted that this procedure had a very low complication rate and allows for a rapid return to performance.
Scientific Article: James, SJ et al. “Long-Term Outcome of Standing Medial Patellar Ligament Splitting to Manage Horses Exhibiting Delayed Patellar Release: Sixty-Four Horses” AAEP Proceedings, vol. 60, 2014, pp. 95-96
Companion Article: Loving, Nancy S. DVM “Surgical Treatment for Delayed Patellar Release Studied,” theHorse.com, June 11, 2015, Article #35923.