|
What is the patella?
 The patella is the kneecap and should be located near the bottom of the femur - upper thigh bone - in the center of the knee joint when looking at it from the front. See drawing at right.
The muscles of the thigh attach to the top of the knee cap and the patellar ligament attaches from the bottom of the knee cap to the tibia just below the knee joint. When the thigh muscles contract, the force goes through the ligaments to the top of the tibia. This straightens of the knee and extends the lower leg.
The patella normally stays in place because the patellar ligament is attached to the midline of the patella and there is a groove in the femur bone that it slides in. If there is a problem with the groove or with where the patellar ligament is attached, the kneecap moves out of its position. Medial luxation -toward the center of the body - is much more common than lateral luxation.
How does it get injured?
Generally this is a problem in small breeds such as Yorkies and Maltese, although it does occasionally occur in larger breeds. These dogs are usually born with this problem. As they grow, the tibia (lower leg bone) starts to bend. This is because the ligaments of the patella (kneecap) restrict the growth of the leg causing it to bend. Without correction, this can become a very severe condition.
How do you decide how bad it is? 
The severity of patellar luxation is graded on scale of one to four. A grade one is the mildest form. In these cases the patella or kneecap is in place more than it is out. A grade four is the worst. In these cases the patella (kneecap) is locked out of place completely. While dogs can walk with this problem, there is a greater risk for severe arthritis and lameness. They’re also at increased risk for other ligament injuries.
How is it diagnosed?
This condition is generally found on physical examination. When you bring in your new puppy, this is one of the things the veterinarian will check for. After diagnosis, we generally recommend that x-rays be taken. This helps us determine how severe the patella problem is - as well as how much bending of the tibia has occurred. X-rays of this type are generally taken while under anesthesia. See photo of x-ray.
What happens if we don't have the surgery?
Without correction, this particular condition can affect your dog’s gait. Sometimes these dogs will skip or hop while walking or running. There can be some pain, especially if arthritis forms. The doctors may try medication in milder cases to control discomfort, but in most of the cases of grades two and above surgery is indicated.
How is the surgery done?
Surgical correction of this problem involves moving the patella and its ligament over into its groove.   On occasion it is necessary to re-groove the femur in order for the patella to have a place to rest. Once moved over, a pin is placed to hold the patellar ligaments in place. Please see drawings. After surgery, recovery will take six to eight weeks. During this time we recommend strict rest with leash walks only. Running or jumping is prohibited. In some cases bandages will be used to ensure the patient’s comfort. In all cases pain management is used. With surgical correction, full recovery is expected in 90% of the cases.
The following link is to a series of photos taken during an actual surgical repair of the MPL. As these are pictures of an actual surgery,
Viewer discretion is advised.
Medial patellar luxation repair
If you have any questions regarding medial patellar luxation or other knee problems, please feel free to contact us. We would be happy to answer all of your questions, and want to ensure that your pet has the best of health. Please call 685-4707.
|