The patella, or knee cap, is a small bone buried in the tendons of the extensor muscles in the thigh. The patella normally rides in a groove within the femur. Patellar luxation is one of the most common orthopedic conditions is dogs, and can be congenital (inherited) or trauma related. Patellar luxation is a condition in which the patella pops out of its groove, either to the inside or outside of the knee, making it quite unstable. This condition can effect only one limb, but often effects both rear legs. MPL can worsen over time from an occasionally popping patella to a chronically luxated kneecap that will no longer return to the patellar groove.
Congenital MPL is diagnosed in 7% of puppies, and is often diagnosed in small breed dogs, such as Yorkshire Terriers, Maltese, Papillon and Miniature Poodles, but is also seen in large breed dogs such as Labrador Retrievers and Great Pyrenese.
MPL is diagnosed through a thorough physical examination, taking into account the patient’s age, heredity and history of injury, as well as it’s overall health. X-rays are taken under general anesthesia in order to provide accurate diagnostic views of the knee.
Some small breed dogs respond well to a period of restricted activity and anti-inflammatory medications. As a general rule, if a dog is still lame following a 2-4 week course of rest and anti-inflammatory medications, or improves and again becomes lame, an MPL procedure is indicated. In most medium and large breed dogs an MPL procedure is eventually necessary to resolve lameness.
Surgical repair of a luxated patella consists of several steps whereby the patellar groove is deepened and the patella is placed back into position within the groove. Surrounding soft tissues and bone are also altered to secure the patella with the groove.
The four goals of a successful MPL repair are:
• To relieve pain associated with the condition.
• To prevent permanent damage to the ligaments and cartilage within the knee.
• To decrease the amount of osteoarthritis which will inevitably develop in the knee.
• To relieve and limit stress put on the opposite limb and other limbs and joints.
All MPL patients will need to spend a minimum of 1-2 days in the hospital following the procedure. This is so pain and discomfort can be controlled using injectable and transdermal medications, as well as to restrict and monitor movement by the patient during this most critical period of recovery.
Once home, owners should do everything possible to limit their dog’s activity, as strict rest is required for proper healing. Initially, there should be no running, jumping or playing, as these can all lead to reluxation of the patella during the healing process. Although rare, reluxation does occur, and often requires further surgery. This is of most concern during the first 8 weeks of recovery, or in patients who suffered from a severe-grade luxation prior to surgery. Any pins used during surgery may need to be removed in 3-12 months. Rarely, a patient will present post-surgically with an “allergic” reaction to the metal from any screws, plates, pins or wire used in the procedure.
Activity should be increased gradually, with short, slow, leashed-walks beginning around the fourth week of recovery. Observation of the patient is absolutely crucial during this period in order to gauge the speed of recovery. Some dogs feel ready to run around and play within the first few weeks, they are not! A full return to normal activity is often allowed within 8-10 weeks, depending on the severity of the initial injury, age, breed, and overall health of the patient.