|
 A luxated patella is where the kneecap is displaced out of its normal position in the knee joint. It may luxate (come out of the "joint") to the inside (medial) or outside (lateral) of the leg.
Some pets are prone to a patella luxation because they have a shallow groove, or no groove at all, where the kneecap normally sits. This variation in anatomy allows the kneecap to "slip out" with movement. Patella luxations are found in both dogs and cats.
|
|
|
What is a patella?
Top
The normal position of the patella (kneecap) is in the centre of the front of the knee. It glides up and down in a groove in the femur (the top leg bone) as the knee bends and extends, and is held in place by the patella ligament. The patella ligament attaches to the top of the tibia (the bottom leg bone).
|
What causes a luxating patella?
Top
Luxating means dislocating, so that a luxating patella moves out of the groove in the femur, usually towards the inside of the knee (medially luxating). If the patella dislocates towards the outside of the knee it is called a laterally luxating patella.
It is usually the result of a congenital problem whereby the point where the patella ligament attaches to the tibia is not on the midline, but more towards the inside of the knee. This means that the patella is pulled towards the inside of the knee each time the knee bends and the patella can be dislocated out of the groove. This can happen intermittently or the patella can be permanently dislocated.
Some dogs also have a shallow groove in their femur that lets the patella move out of its central position more easily. Also, over time the inner side of the groove wears down due to constant movement of the patella over it, and the problem worsens.
A luxating patella can also be a result of trauma.
|
What are the signs of a luxating patella?
Top
There are four grades of luxating patella depending on the severity of the problem. Clinical signs related to patella luxation depend on the grade of luxation, amount of arthritis present, how long the disease has been left untreated, and the presence of other knee joint abnormalities. A pet with a grade I patella luxation has a kneecap that is loose but tends to stay in its normal position. A pet with a grade IV luxation has a kneecap that is permanently out of its normal position.
Toy and small breed dogs with medially luxating patellae tend to have both sides affected.
Common signs to look for include:
|
-
- The affected leg is intermittently carried with the knee joint flexed
- Persistent, abnormal hindleg carriage and function in neonates and puppies
- Occasional "skipping" hindleg lameness
- Sudden signs of lameness following minor trauma
- Crouching, bowlegged or knock-kneed stance
- There may be no signs, and the diagnosis may occur during routine physical examination by you veterinarian
|
What is the treatment?
Top
Treatment depends on the severity of the problem. Low-grade problems of short duration are usually treated medically with anti-inflammatory painkillers and rest. If the problem persists, or the luxation is more severe, surgery may be recommended.
The aim of surgery is to correct the underlying anatomical defects by moving the point of attachment of the patella tendon on the tibia to a more central position, by deepening the groove in the femur in which the patella sits, and by tightening the joint capsule around the knee.
The prognosis after surgery is excellent except if significant arthritis is present. Therefore if your dog is diagnosed with a luxating patella and surgery is recommended, it is better to have this done sooner rather than later when secondary degenerative joint disease (arthritis) has occurred.
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dr Julia Adams BVSc
Dr Rebecca Bragg BVSc MACVS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
