Before the equine hind limb can fold, the kneecap (patella) must be lifted off a locking ridge on the end of the femur. It is akin to a release latch on a folding table. If the patella is not lifted properly, the whole limb remains locked. In the condition “locking patella”, the stifle remains locked until it pops loose or it is dislodged by someone who knows how to unlock it.
Intermittent upward fixation of the patella is a mild variation on locking patella. Here, there is just a transient catch of the patella on the medial trochlear ridge of the femur. Riders may complain of a “catch” or “snap”, lameness, poor performance, or a sense of the horse collapsing or falling away behind. Horses that have this condition may snap their feet upward in a stringhalt-like gait.
Horses with this syndrome often have straight hind limb conformation, and poor body condition or muscle tone. It is common in young, undeveloped horses, and those that are convalescing and have lost muscle tone.
The diagnosis requires a lameness exam and can be difficult. Radiographs usually do not show a problem, unless there is other injury to the stifle causing bony changes.
Treatment includes conditioning and strengthening exercises, usually trotting over cavilleti or up long hills, movements that help to strengthen the quadriceps muscle group. There are a variety of other more aggressive treatments.
Other Diagnoses Considered
Treatments May Include
Prognosis & Relevant Factors
The prognosis is good with conditioning exercises in most cases. It depends on whether there are other problems in the stifle as well.
I Might ObserveRelated Observations
Skills I might need
QUESTIONS TO ASK MY VET
Helpful Terms & Topics in HSVGWritten, Reviewed or Shared by Experts in Equine Health