The patella is the kneecap. It sits at the front of the knee joint, and in a healthy dog it slides up and down in a groove. In patella luxation, the kneecap slips out of that groove. It can slip to the inside, which is called medial, or to the outside, which is called lateral.
What causes it
Medial patella luxation is considered an inherited condition and often shows up in puppies. Lateral patella luxation is less well understood. Its heritability is not known, and it usually appears later in life, around five to eight years of age.
Signs to watch for
Both knees are often affected, though one-sided cases are not rare. Some puppies show signs by eight weeks of age. The most obvious sign is a knock-knee stance. The kneecap can often be put back in place by hand, and the ligaments around the knee may feel loose. The inner tissues of the joint can be thickened, and the foot may twist outward as the dog puts weight on the leg.
With medial luxation, the back leg may be carried oddly, or the dog may suddenly go lame. How bad it looks depends on the grade.
- Grade 1 and 2: lameness appears only when the kneecap is out of place. The leg is held with the knee bent, but the dog may touch the ground every few steps when moving fast.
- Grade 3 and 4: the dog crouches, the legs bow outward, the feet turn inward, and most of the weight shifts to the front legs. If the kneecap stays out, the muscles that straighten the leg stop working properly. Some dogs are in pain, but many do not seem to mind being handled.
Lateral luxation can come on quickly, sometimes after minor trauma or hard play. The knock-knee stance is typical, sometimes described as seal-like. If both knees slip out at once, the dog may not be able to stand, and it can look like a nerve problem.
Treatment
Fixing the problem usually means orthopaedic surgery, and it is normally recommended for the higher grades, three and above. For dogs with milder grades, small changes at home help a lot. Ramps, pet stairs and steps take strain off the knees and reduce pain and further damage.
How dogs are checked
The vet examines the dog while it is awake. Chemical restraint is not recommended for this, because the dog needs to move naturally. The vet then grades the patella and fills in the OFA application form with the result.
The form and fee go to the OFA. Owners and vets are encouraged to send in every evaluation, normal or abnormal, so the data stays complete. There is no OFA fee for recording an abnormal patella result.
Advice for breeders
Dogs can be evaluated before twelve months if the owner plans to breed early. The best time to collect breeding data is at six to eight weeks, before the puppy goes to its new home.
A breed database number is issued to dogs found normal at twelve months or older. The number records the age at evaluation. Because some luxations only show up later, dogs should be re-checked from time to time.
What the numbers say for our breed
From 1974 to 2012, the OFA received 1,316 patella evaluations for Coton de Tulear dogs. Of those, 95 percent were normal and 5 percent were abnormal.
These figures are from the old record. As of 2026 the club encourages breeders to keep testing and to share results openly. If you are buying a puppy, ask whether the parents were checked and what the grades were.
If you have questions about patella luxation, or you are not sure what a grade means for your dog, please write to us, call us, or come and visit us at a club event.
Source: Orthopedic Foundation for Animals (OFA).
