Luxating Patella or Floating Kneecap – Patellar Luxation
What is the Patella?
The patella is the bone we know as the knee cap. The knee cap for dogs and humans both sit in the same place A groove in the end of the femur allows the patella to glide up and down when the knee joint is bent back and forth. The patella guides the action of the quadriceps muscle in the lower leg. The patella also protects the knee joint.
What Happens when the patella is luxated?
Luxating Patella or floating kneecap chihuahuas and small breed dogs, the patella could luxate because of malformation or trauma, the ridges forming the patellar groove are not prominent, and a too-shallow groove is created. In a dog with shallow grooves, the patella will luxate (jump out of the groove) sideways, especially toward the inside. This causes the leg to ‘lock up’ with the foot held off the ground.
When the patella luxates from the groove of the femur, it usually cannot return to its normal position until the quadriceps muscle relaxes and increases in length. This explains why the affected dog may be forced to hold his leg up for a few minutes or so after the initial incident. While the muscles are contracted and the patella is luxated from its correct position, the joint is held in the flexed or bent position. The yip is from the pain caused by the kneecap sliding across the bony ridges of the femur. Once out of position, the animal feels no discomfort and continues his activity.
What are the symptoms of Luxating Patella?
Most dogs are middle-aged, with a history of intermittent (on-again-off-again) lameness in the affected rear leg(s). An affected dog commonly stops and cries out in pain as he is running. The affected leg will be extended rearward, and for a while the dog is unable to flex it back into the normal position.
Severity of Patella Luxation
- Grade 1 – Luxating Patella describes a kneecap that pops out (or can be manually popped out of place), sometimes requiring manual manipulation to re-set it.
- Grade 2 – Luxating Patella describes a kneecap that pops out of place and doesn’t always pop back in automatically, sometimes requiring manual manipulation to re-set it.
- Grade 3 – Luxating Patella describes a kneecap that sits outside its groove most of the time, but can be manually positioned back in the groove, where it stays temporarily.
- Grade 4 – Luxating Patella describes the worst case scenario, in which the kneecap sits outside the groove all the time, and will not stay in the groove when it is manually popped back into place.
What are the risks?
Uncorrected, the patellar ridges will wear, the groove will become even shallower, and the dog will become progressively more lame. Arthritis will prematurely affect the joint, causing a permanently swollen knee with poor mobility. Therefore, a good evaluation needs to be done by your veterinarian early in the condition to prevent long-term arthritic crippling.
Treatment for Luxating Patellas
As would be expected, medical therapy has little corrective ability in this disorder and surgery is therefore required and is the treatment of choice. A surgical treatment is not necessary in every individual with this condition.
Surgery can alter both the affected structures and the movement of the patella. The groove at the base of the femur may be surgically deepened to better contain the knee cap. This procedure is known as a trochlear modification. The knee cap itself may be “tied down” laterally to prevent it from deviating medially. This is called a lateral imbrication. The bony protuberance at the site of the attachment of the quadriceps tendon on the tibia may be cut off and then re-attached in a more lateral position. This is termed a tibial crest transposition. All of these procedures work well and the type performed depends on the individual case and the clinician. The animal should respond quickly after surgery and is usually completely recovered within 30-60 days, depending upon the procedure.
Tips to help your dog:
- Achieve and maintain a healthy weight
- Exercise your dog accordingly
- Use an oral joint supplement
- A specific diet for your dogs joints
A genetic predisposition to luxating patellas occurs in a variety of small and tiny dogs, including:
- Miniature and toy Poodles
- Jack Russell Terriers
- Boston Terriers
In certain breeds that have extremely short legs such as the Basset Hound or Dachshund, patellar luxation is thought to be secondary to the abnormal shape of the femur and tibia. The curvatures of the bones in these breeds work in conjunction with the forces of the quadriceps muscles to displace the patella to the inside. Please do not misunderstand – not all members of these breeds are affected with patellar luxation, only a small portion.
Smaller breeds of dogs, especially Miniature and Toy Poodles, have the highest incidence of patella luxation. Genetics can play a role.
No Breeding Luxating Patellas
Because of the strong genetic relationships, Pet it feels that animals with this disorder should not be used for breeding. They can still be excellent pets and those that do require surgery will usually lead perfectly normal lives without any restrictions on activity. Pet it Chihuahuas does not breed any chihuahua with luxating patella.