This condition occurs when the patella moves out of the groove of the femur in which it slides normally during the flexion and extension of the knee. It can return into the groove spontaneously or remain dislocated more or less long. In very extreme cases, it never goes back into place at all. The luxation causes limping that is often intermittent and which, long term, can lead to the development of osteoarthritis.
The luxation of the patella can occur following a trauma or be congenital (the animal is born with an abnormal conformation of the knee which allows the patella to luxate). Given that the congenital luxation is probably hereditary, it is not advised to reproduce these animals.
There exists a classification to differentiate the luxation and help us to determine the severity, possible treatments and the long term prognosis.
Classification of patellar luxation:
Grade 1: intermittent luxation associated with occasional limping. The patella can be manually dislocated but falls immediately back into place. Absence of bone modification.
Grade 2: intermittent but frequent luxation associated with limping with a bent limb. The patella can fall back into place spontaneously or immediately.
Grade 3: permanent luxation of the patella associated with a medial rotation of the tibia. The luxation may be reduced manually but returns immediately.
Grade 4: permanent and irreducible luxation of the patella.
The treatment of a patellar luxation may be either conservative (without surgery) or surgical, all depending upon the symptoms and grade of the luxation.
It consists of keeping the dog at rest. We recommend it when the luxation can restore itself (grade 1 and 2). However, even in these cases, two complications can arise over the long term: the appearance of osteoarthritis and the rupture of cruciate ligaments. Glucosamine can be given to help preserve the cartilage.
In cases where the luxation is more serious, intervention is necessary (grade 3 and 4 and if the luxation is harming your dogs’ quality of life).
There exists several surgical treatment possibilities depending on the stage of the luxation. The surgery consists of stabilizing the joint of the patella in diverse ways:
- By simply hallowing out the femoral trochlea so that the patella fits into it better and the joint is more stable.
- By hallowing out the trochlea in which we associate a transposition of muscles: this consists in taking a piece of muscle and fixing it at the level of the joint to stabilize it.
- By hallowing out the trochlea in which we associate a transposition of the tibial crest. This time it consists of taking a piece of bone from the tibia to stabilize the joint.
Patellar luxation in the Chihuahua, the Boston terrier, the Pomeranian, the miniature poodle, the Yorkshire terrier, etc. (Patellar luxation is also a congenital disease)
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