Medial Patellar Luxation in Cats and Dogs during Surgery

by | Dec 6, 2021

medial-patellar-luxation

Medial Patellar Luxation in Cats and Dogs during Surgery

What is patellar luxation?

Patellar luxation is a condition that affects the stifle (knee) joint. It occurs when there is an alignment problem in the pelvic limb. The result is that the pull of the quadriceps on the patella  causes it to move or track in an abnormal/luxated location. 

The direction of the luxation is commonly medial (towards the inside of the joint). But, sometimes, it can be lateral (towards the outside of the joint). When the patella is in a luxated position the patient will often hop or skip on the leg. When the patella moves in and out it can damage the articular cartilage. This can then result in pain and osteoarthritis development. It can also increase the risk of cranial cruciate ligament rupture/injury.

What is the grading system for patellar luxation?

The grading system is used to characterise the severity of the luxation and ranges from grade 1-4. 

  • Grade 1: The patella is in all the time but can be forced out/luxated. It will spontaneously reduce to a normal position. 
  • Grade 2: Patella is in most of the time. It can spontaneously luxate but it wants to stay in place most of the time. 
  • Grade 3: Patella is out most of the time but can be reduced with palpation of the joint/patella. 
  • Grade 4: The patella is out all the time and cant be reduced. This grade can be associated with more severe angular changes in the joint, tibia and femur. In some cases there is a marked lameness, in others the lameness is mild. 

How is a patellar luxation diagnosed?

Patellar luxation is most commonly diagnosed with palpation of the stifle (knee) joint. The patella can often be palpated moving into an abnormal location. In severe cases of patellar luxation the patella is abnormally located the entire time and can not be reduced into a normal location. Once diagnosed, the luxation is graded according to severity, in which grade 1 is the least severe and grade 4 is most severe. 

Imaging studies such as radiographs are often performed to assess for evidence of osteoarthritis as well as any bone abnormalities. In some cases, a  CT scan is performed to look more closely at the shape of the bones and to assess the alignment of the entire leg.

How can I tell if my pet has patellar luxation?

In some cases you will not notice any issues in your pet. In other cases there will be a ‘hopping or skipping’ type lameness where the patient will hold the limb off the ground and skp for a few steps while the patella is luxated. When the patella is reduced the lameness is often resolved.

How Did My Dog or Cat Get a Luxating Patella?

The reason that your pet has a patellar luxation is related to an alignment issue between the quadriceps muscles, the patella, the patellar tendon and the attachment of the patellar tendon on the tibial tuberosity. The pull of the quadriceps when the alignment is out causes the patella to luxate.  The reason for the malalignment typically has a genetic basis and this has contributed to an abnormal development of the skeleton and soft tissues. 

Does a luxating patella cause any long-term problems for my cat?

When the patella (knee cap) luxates, it can damage cartilage on the underside of the patella and on the femoral trochlea (the groove where the patella sits). This cartilage damage can lead to osteoarthritis development and progression and can be a reason for lameness in the affected leg. In addition, when the patella is in a luxated (abnormal) location it is possible for injury/damage to the cranial cruciate ligament to occur.

How to Prevent Luxating Patella in Cats

Unfortunately there is little that can be done to prevent patellar luxation from occurring. The reason that the patella luxates is related to an alignment issue between the quadriceps muscles, the patella, the patellar tendon and the attachment of the patellar tendon to the tibial tuberosity. Ultimately the only way to manage the patellar luxation is with surgical intervention. 

Could delaying treatment do more damage?

When the Patella (knee cap) luxates it can damage cartilage on the underside of the patella and on the femoral trochlea (the groove where the patella sits). This cartilage damage can lead to osteoarthritis development and progression and can be a reason for lameness in the affected leg. 

In addition, when the patella is in a luxated (abnormal) location it is possible for injury/damage to the cranial cruciate ligament to occur.  Delaying the treatment can cause an increase in the amount of cartilage damage that is seen and also can increase the risk of cranial cruciate ligament injury/degeneration.

Will my dog be able to exercise normally after patellar luxation surgery?

Once your dog has completed the recovery from surgery they should be able to return to normal or very near normal function. 

What is post-operative recovery and care for medial patellar surgery in cats and dogs?

The exact recommendations for post-operative recovery will depend on the surgeon and the extent/type of surgery that is performed to correct the luxation. It will also depend on whether one or both legs are operated at the same time. 

Typically an 8 week period of restriction is needed. During this time your pet should be confined to a small area of the house. There should be no ‘fun’ during this time i.e. no running, playing, jumping, getting on and off furniture, no other animals or small children. 

There is an amount of activity allowed in the post-operative period. However, all activity needs to be controlled. Typically a tapered increase in short leash walks is recommended from the second week post operatively. This generally starts with 5 min of leash walking in the second week post operatively and builds by 2-3 minutes each week providing there is no progression of lameness/deterioration in condition. 

Does my pet have to stay at the hospital overnight?

This will depend on the hospital and the surgeon. In most cases an overnight stay in hospital is recommended to allow adequate pain relief to be administered.

How long until my pet is back on their feet?

Following surgery the recovery period is typically 8 weeks. At this time a radiograph of the limb will be taken to confirm that the bone has healed as expected at this point an increase to normal activity can occur.

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