What you need to know about upward fixation of the patella
Sticky Stifle Management
Does your horse have that notorious “sticky” stifle? Did your trainer say that your horse “just isn't right” or has a “hitch in his giddy-up?” We may have heard these statements, but what may be truly occurring is an upward fixation of the patella (UFP).
The patella is located in the stifle at the intersection of the femur and tibia. The patella rests on the medial trochlear ridge of the femur, which is important for the passive stay apparatus. This unique feature allows the horse to rest standing with minimal effort. A problem occurs when the patella does not disengage properly from the medial trochlear ridge and the leg appears “stuck” or “sticky” and the limb may even remain in extension.
We have seen mild to severe UFP in dressage horses. Mild UFP has jerky movements due to a delayed release of the patella. Severe UFP can be seen as an extension of the limb behind the horse because of a locked patella.
The precise cause of UFP is not completely known. One study suggests that it is the spasmodic or tonic activity of the vastus medialis of the quadriceps femoris muscle. We do know that the risk factors for UFP can include poor conformation, poor conditioning, genetics and poor foot conformation (high medial hoof-wall height and long toes). The condition is most commonly identified in young, untrained horses and adult horses who may be out of work and losing muscle rapidly. Surgery to correct the problem is most common in warmbloods (31.8 percent) followed by Standardbreds (18 percent), Arabians (11.8 percent), Icelandics (9.4 percent), Thoroughbreds (7 percent), ponies (8.3 percent) and Friesians (4.7 percent). The same study identified a median age of 7 years and the most common disciplines were pleasure (48.2 percent) followed by dressage (17.6 percent).
UFP may occur as a unilateral or bilateral hind-limb condition and can be either intermittent or permanent in nature. Conservative and surgical treatments have been studied and applied to horses. It is always important to have a proper diagnosis from your veterinarian prior to instituting any therapy.
Conservative treatment usually is instituted if the condition is not creating a lameness and is intermittent. Treatments include corrective trimming and shoeing, conditioning, chiropractic, acupuncture/ aqua puncture, pro lo therapy, pharmaceutical intervention( anabolic steroids andc hon dro protectives) and io dine-containing counterirritants. Conditioning can include hill work both diagonally and perpendicular in direction. Corrective trimming and shoeing may involve shortening the toe to improve a negative plantar angle, correcting medial-lateral balance, elevating the lateral heel and rounding the medial toe. Pharmaceuticals are estrogen compounds (hormonal therapy) given in the muscle and can theoretically increase the tension of the supporting soft-tissue structures helping to change the position of the patella.
As a veterinarian, I will generally start with a combination of conservative treat- ments, especially in a young horse prior to maturation. If the conservative treatment is not providing the desired success, surgical options can also be provided.
Surgical treatment includes a minimally invasive surgical procedure called medial patellar ligament splitting/fenestration, which can be completed in a standing position. A more invasive surgery is the medial patellar ligament desmotomy, which is typically completed under general anesthesia. In either case, a two-week rehabilitation may be needed for improvement or resolution after surgery.
A recent retrospective study found that surgery (recumbent or standing) provided a 97.6 percent complete resolution either immediately or after up to two weeks of rehabilitation. No short- or long-term complications were reported.
Upward fixation of the patella can be a concern in your dressage horse, but know that a myriad of conservative and ultimately surgical options can be provided with good success. Many successful dressage horses have overcome UFP.