Patellar Luxation (Loose Knees)
Patellar Luxation (Loose Knees)
Cavalier King Charles spaniels may suffer from a recurring hereditary condition which causes luxating patellas -- loose knee caps. PatellaThe disorder is believed to affect as many as 20% of cavaliers. The patella is the dog's knee cap. It should be located in its groove in the center of the stifle (knee joint) of the femur (upper leg bone). A luxating patella is a knee cap that moves out of its groove. It also may be called a floating kneecap. Genetic conditions which cause patellar luxation are a shallow groove, weak ligaments, and misalignment of the muscles and ligaments between the femur, patella, and tibia (lower leg bone).
In some cases of this disorder, there are no symptoms and therefore pose no physical problem. These cases are called "occult" conditions. In others, the symptoms are apparent. These cases are referred to as "clinical". In these clinical cases, if the condition is not corrected, it may degenerate: the patella's ridges will wear, its groove will become shallower, and the cavalier will become progressively more lame. Arthritis will prematurely affect the joint, causing a permanently swollen knee with poor mobility.
Possible Cause
It is generally accepted that luxating patellas are an hereditary condition in the CKCS and some other canine breeds. In veterinary research studies, the disorder has been associated with an hereditary lack of sufficient, normal collagen fibers in the dogs' ligaments and tendons. Ehlers-Danlos syndrome (EDS) is an hereditary connective tissue disease in which the skin is easily torn and there is excessive laxity in the ligaments of joints connecting the dogs' bones, such as the ligaments between the patella and the femor.
In a July 2018 article in which nine dogs (none were cavaliers) with patellar luxation were studied with five normal dogs as the control group. The researchers concluded that patellar luxation in dogs is associated with collagen fiber abnormalities similar to those observed in humans with EDS. See also this 1987 study of a CKCS-mix dog with a similar diagnosis of EDS, although luxaing patellas were not reported among the indications.
Symptoms
When the loose knee cap pops out of its socket, the dog may hold up its affected hind leg or stretch the leg out or just stop moving and sit down. The dog may also whimper or cry out in pain. Signs vary, and in some cases, the knee cap will re-insert itself, and the dog will move on as if nothing has happened. In other cases, the knee cap will not return spontaneousy, and manual pressure may be required. In the most severe cases, the knee cap will not return despite manual manipulation. See the Grades of Severity below.
Diagnosis
X-ray of cavalier's displaced right patellaManipulation: Veterinarians can check for patellar luxation by manipulating it. The dog is examined awake and the veterinarian classifies its degree of luxation. Adult cavaliers should be evaluated annually, and puppies should be examined at 6-8 weeks of age prior to their release to the new owners.
X-ray: X-rays (radiographs) can confirm a displaced patella. The relocation of the patella can be observed in the x-rays as being either towards the center-line of the dog's body (called medial patellar luxation or MPL) or in the opposite direction (called lateral patellar luxation).
Cavalier King Charles spaniels may suffer from a recurring hereditary condition which causes luxating patellas -- loose knee caps. PatellaThe disorder is believed to affect as many as 20% of cavaliers. The patella is the dog's knee cap. It should be located in its groove in the center of the stifle (knee joint) of the femur (upper leg bone). A luxating patella is a knee cap that moves out of its groove. It also may be called a floating kneecap. Genetic conditions which cause patellar luxation are a shallow groove, weak ligaments, and misalignment of the muscles and ligaments between the femur, patella, and tibia (lower leg bone).
In some cases of this disorder, there are no symptoms and therefore pose no physical problem. These cases are called "occult" conditions. In others, the symptoms are apparent. These cases are referred to as "clinical". In these clinical cases, if the condition is not corrected, it may degenerate: the patella's ridges will wear, its groove will become shallower, and the cavalier will become progressively more lame. Arthritis will prematurely affect the joint, causing a permanently swollen knee with poor mobility.
Possible Cause
It is generally accepted that luxating patellas are an hereditary condition in the CKCS and some other canine breeds. In veterinary research studies, the disorder has been associated with an hereditary lack of sufficient, normal collagen fibers in the dogs' ligaments and tendons. Ehlers-Danlos syndrome (EDS) is an hereditary connective tissue disease in which the skin is easily torn and there is excessive laxity in the ligaments of joints connecting the dogs' bones, such as the ligaments between the patella and the femor.
In a July 2018 article in which nine dogs (none were cavaliers) with patellar luxation were studied with five normal dogs as the control group. The researchers concluded that patellar luxation in dogs is associated with collagen fiber abnormalities similar to those observed in humans with EDS. See also this 1987 study of a CKCS-mix dog with a similar diagnosis of EDS, although luxaing patellas were not reported among the indications.
Symptoms
When the loose knee cap pops out of its socket, the dog may hold up its affected hind leg or stretch the leg out or just stop moving and sit down. The dog may also whimper or cry out in pain. Signs vary, and in some cases, the knee cap will re-insert itself, and the dog will move on as if nothing has happened. In other cases, the knee cap will not return spontaneousy, and manual pressure may be required. In the most severe cases, the knee cap will not return despite manual manipulation. See the Grades of Severity below.
Diagnosis
X-ray of cavalier's displaced right patellaManipulation: Veterinarians can check for patellar luxation by manipulating it. The dog is examined awake and the veterinarian classifies its degree of luxation. Adult cavaliers should be evaluated annually, and puppies should be examined at 6-8 weeks of age prior to their release to the new owners.
X-ray: X-rays (radiographs) can confirm a displaced patella. The relocation of the patella can be observed in the x-rays as being either towards the center-line of the dog's body (called medial patellar luxation or MPL) or in the opposite direction (called lateral patellar luxation).