One of the most common health problems in Maltese and many other toy dogs is luxating patella (LP), a condition where the kneecap literally slips out of the groove, becoming dislocated.
Luxating patellas are considered primarily an inherited congenital disorder. Usually within the first year, the patellas will begin slipping out of place. A luxating patella can also occur from a trauma or injury. An injury will generally involve just the one knee. If both knees are affected, one should suspect an underlying genetic component.
There are several things that can cause patellas to become loose with time: The ligaments, which hold the patellas in place, begin to weaken or the groove holding the patella is too shallow. Or, the tibia and/or femur could be improperly curved and not aligning properly, causing the patella to become unstable. It can be gradual process where the owner does not notice anything, or it can be a sudden dislocation where the puppy will yelp and become lame. Sometimes this sudden luxation is mistaken for an injury when in fact it is not.
Luxating patellas are graded from I to IV. Grade I is the mildest. The patella can be pushed out but will immediately “pop” back into the groove on its own. Grade IV is the most severe with the patella being permanently dislocated.
Fortunately, for the vast majority of Maltese with luxating patella(s), they tend to be in the milder category with Grade I or II.
A dog with a mild grade of LP usually does not require surgery. Keeping the weight down, avoiding slippery surfaces and preventing the dog from doing a lot of jumping (e.g., on and off the furniture) will all help lower stress on the joint. Despite this, arthritis is a likelihood in the later years of life. Severe LP, or a patella that has been forced to dislocate by trauma, will normally necessitate surgical repair. A veterinarian or orthopedic surgeon can determine the best course of action.
All Maltese should have their patellas palpated manually by their veterinarian. For breeders, this should be mandatory. No breeding should take place without knowing the status of the patellas of the potential parents.
Because of the complexity of inheritance (polygenic) and the fact that LP is “in” the breed, it is impossible to guarantee a breeding won't produce offspring that develop LP. However, by breeding two parents with tight patellas, the incidence will be greatly reduced. Likewise, breeding two dogs with LP will greatly increase the chance of the offspring developing the condition. Common sense would dictate not to breed together two dogs with LP.
The Orthopedic Foundation for Animals (OFA) offers patella certification. X-rays are not required and any experienced veterinarian can do the palpation for the certification. With time, it is hoped that more Maltese breeders will utilize the OFA service just as breeders of larger dogs prone to hip dysplasia do.
The American Maltese Association is proud to include OFA certification for patellas as one of our CHIC breed requirements.