The patella, or kneecap, is part of the stifle (knee) joint. The patella is normally located in a groove on the end of the femur (thigh bone) just above the stifle (knee). The term luxating means ‘out of place’ or ‘dislocated’. In patellar luxation, the kneecap, which normally sits on the groove of the femur, moves or pops out of place, either in a medial (inward) or lateral (outward) position.
A luxating patella can occur from a traumatic injury but more commonly is associated with joint or limb structure abnormalities, such as the groove of the femur where the kneecap sits being too shallow, or the area where the kneecap attaches to the shinbone (tibia) is off-center. These limb and joint changes result in an alteration of forces placed on the knee and, in turn, luxation of the patella.
For many toy or small breed dogs such as Yorkshire terriers, Chihuahuas, Miniature Poodles, and Pomeranians, there is a genetic predisposition for developing a luxating patella. In most small breed dogs, this movement occurs medially or toward the inside of the limb. A luxating patella can happen laterally or toward the outside of the limb, but this is less common and usually only occurs in larger breeds.
When the patella luxates, your pet may have difficulty bearing weight on the leg and you may notice a skip in their step or see them running on 3 legs. They may learn how to kick the leg to the side, which can pop the patella back into its normal position and suddenly they will be back on all four legs as if nothing happened.
If you suspect your pet may have a luxating patella, you should schedule an appointment with your veterinarian because early detection can help your pet recover more quickly and can prevent other problems such as lameness and arthritis.
Your veterinarian should perform a physical exam and check for any instability in your pet’s kneecap and identify any signs of pain. Watching your pet walk may help your veterinarian observe any abnormalities associated with your pet’s gait.
X-rays may also be taken to help confirm and assess the knees for patella luxation. The X-rays will help identify the severity of a patella luxation as well as any other underlying or concurrent problems.
This depends upon the grade of the luxation and whether both legs are affected to the same degree. There are several degrees of patella luxation, graded from I-IV. In affected pets, one or both kneecaps may luxate, sometimes to a different degree. Approximately 50% of affected dogs have both knees involved while the other 50% have only one knee involved. Some pets may tolerate this condition for many years, even for their entire life.
However, patella luxation can predispose the knee to other injuries, such as cruciate ligament tears, other muscle or joint pain, and arthritis. The weight-bearing stress on the leg is altered by having a patella luxation and can lead to changes in the hips, thigh, and shin bones. In addition, as the pet ages, arthritis will develop and can result in decreased mobility and joint pain.
If your pet has been diagnosed with a patella luxation, there are many things you can do to help keep your pet comfortable.
For mild patella luxation, physical therapy and exercise can help train and strengthen your pet’s leg muscles to prevent the patella from slipping out of place. Maintaining a healthy weight can also help reduce the stress that the extra pounds can add to the knees. Sometimes, a veterinarian may prescribe anti-inflammatory or pain relief medication to help ease your pet’s pain symptoms and discomfort.
However, depending on the grade of patella luxation, surgery is occasionally required to help correct the condition, prevent lameness or secondary injuries and reduce pain. To schedule a consultation to see if your pet would benefit from surgery, please click here to schedule an appointment today.
If surgery is performed before arthritis or another knee injury occurs the prognosis is excellent. After full recovery from surgery, your pet should regain full use of the leg. However, if arthritis has already developed in the knee joint, your pet may experience intermittent pain in the leg and the arthritis may progress. The more severe the grade of luxating patella, the higher the likelihood of reoccurrence postoperatively.
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