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Medial Patellar Luxation in Dogs

A luxating patellar is when the knee cap moves from its normal position. The patella (knee cap) is in a cartilaginous groove at the end of the femur at the stifle. The patella in dogs is an almond shape and its purpose is to assist in the extension of the knee. The patella resides in the tendon of the quadriceps muscle group which attaches to the bone below the femur, the tibia. If this muscle group contracts, it pulls on the tendon and the knee cap, thereby extending the stifle. If the patella is moved out of its groove with knee extension, it is called a luxating patellar.

The causes of this condition can be congenital, genetic and/or traumatic. Breeds with a predisposition for luxating patellar are Yorkshire Terriers, Pomeranians, Pekingese, Miniature and Toy Poodles, Maltese, Jack Russell Terriers Chihuahuas, Cavalier King Charles Spaniels, Papillons and Boston Terriers. Large breed dogs are prone to this condition, they include Labrador Retrievers, Golden Retrievers, Akitas, Malamutes, Boxers, Huskies and St. Bernards. Apart from breeding, if a dog has poor conformation, such as weak hocks - then this can also cause a luxating patellar.

The initial symptoms can include limping, a skip in the gait, loss of support on the limb, abnormal posture with the knee placed outward; all of which are usually intermittent. Sometimes, acute cases can lead to erosion of the cartilage on the femur from the constant friction, and eventually, to osteoarthritis. In this case, pain is usually involved and the lameness is more constant and severe.

A luxating patellar can lead to a ruptured cranial cruciate ligament. The literature states that at least 15% to 20% of dogs with patellar luxation will eventually rupture their cranial cruciate ligament. Two main reasons why this scenario may follow are:

  1. a luxating patellar will change the biomechanics of the knee and subject the cranial cruciate ligament to more stress and strain, and
  2. if the luxating patellar is chronic with arthritic changes, the inflamed environment inside the joint will cause a breakdown of the ligaments (especially cruciate ligaments).

A luxating patellar is usually diagnosed by feel and is assigned a grade based on the severity of the condition. Grade 1 is the least severe and the knee cap easily slips back into place on its own whereas Grade 4 means the knee cap is actually stuck and fixed outside its normal resting position in the groove of the femur. An x-ray of the stifles can be performed to see if there is osteoarthritis present or any sign of cranial cruciate ligament damage.

Surgery is not always necessary for this condition. Many small dogs live their entire life with luxating patellar and it never results in arthritis or discomfort, nor does it interfere with the dog's life. Grade 3 or 4 luxations normally require surgery as greater pain or discomfort will be involved, along with loss of mobility of the leg or associated injury such as a cranial cruciate ligament rupture.

Zoomadog sells some great products to help rehabilitate your dogs after surgery or injury. We have cruciate knee braces, dog hip braces, leg supports and many other dog mobility products. We can supply you with a rehabilitation book to assist you after you dog has had surgery, this includes our Medial Patellar Luxation home therapy guide This gives you full week by week instructions on how to rehabilitate you dog after surgery.

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