Knee Surgery (MPL)

There are specialized surgical procedures that are most often used to correct patella luxation:

• MPL Surgery:  When the patellar luxation occurs toward the medial (inward) of the knee this tissue must be released (retinacular release) to allow the patella to return to its normal location and the tissue on the lateral (outward) side of the knee must be tightened (fascial imbrication) to keep the patella in place.
• Trochleoplasty:  The normal groove that contains the patella often has to be deepened to maintain the patella in the proper location. 
• Tibial tuberosity:  The attachment of the patellar tendon must be realigned with the remainder of the limb by cutting the bone and moving the tuberosity to a more normal location. 

Patellar luxation (dislocation) is a condition where the kneecap rides outside the femoral groove when the knee is flexed. It can be further characterized as medial or lateral, depending on whether the knee cap rides on the inner or on the outer aspect of the knee respectively.

Patellar luxation is one of the most common orthopedic conditions in dogs, diagnosed in 7% of puppies. The condition affects primarily small dogs.  Patellar luxation affects both knees in half of all cases, potentially resulting in discomfort and loss of function.  Patellar luxation occasionally results from a traumatic injury to the knee, causing sudden severe lameness of the limb. Because there is evidence that this condition is at least in part genetic, dogs diagnosed with patellar luxation should not be bred.

Even though your pet may have patellar luxation it may or may not require surgery. We recommend correction of patellar luxation in patients that are experiencing pain and lameness secondary to the luxation. You may notice that your dog skips on the affected leg or holds it up when running or walking. They may also stretch the leg backwards in order to replace the patella back in its normal location. 

Symptoms associated with patellar luxation vary greatly with the severity of the disease:

• Your veterinarian may detect this condition during one of your dog’s physical exams.
• You may notice your pet “skipping”, carrying up the affected leg up a few steps.  Most dogs affected by this disease “skip”, and may be seen shaking or extending the leg prior to regaining its full use. 
• As the disease progresses in duration and severity, this lameness becomes more frequent and eventually becomes continuous. 
• In young puppies with severe medial patellar luxation, the rear legs often present a “bow-legged” appearance that worsens with growth. 
• Large breed dogs with lateral patellar luxation may have a “knocked-in knee” appearance.

• Grade I – Pets with Grade I luxations (the patella unstable but remains inside of the groove most of the time) may show lameness with activity but are not lame at other times. While generally not problematic, Grade I can be painful to pets who are not used to the patella luxating out of place.  
• Grade II – Pets with grade II luxations (patella luxates out of position but will go back to the proper position by itself) occasionally carry the limb up for a few steps (“skipping”)  and may be seen shaking or extending the leg prior to regaining full use. Some patients even appear to “improve” when their lunation progresses from grade I to grade II. As the disease continues to cause arthritis and rotation at the knee, this lameness becomes more frequent and eventually becomes continuous.
• Grade III – Pets with Grade III (patella usually remains luxated but can go back into place sometimes) experience frequent lameness. Pets often experience ACL tears due to the stress on the ACL with the knee constantly in rotation.
• Grade IV – Pets with grade IV luxations (permanently luxated and cannot go back into place) tend to walk in a “crouched” position because they are unable to extend the knee properly. ACL tears are often a cause of having a permanently luxated patella.