Dog Patella Luxation

Diagnosis

Patella Luxation (also known as patella or kneecap dislocation) is a common orthopaedic condition in dogs and is easily diagnosed. The condition is more common is smaller dogs but occasionally seen in larger dogs. Cats can also have luxating patellas and present with similar signs as in the canine.

The patella (commonly known as the kneecap) usually rides in a groove called the trochlear groove. Patella luxation occurs when the kneecap is forced to ride outside of this groove.

- Developmental or Congenital Medial Patella Luxation. This presentation is the more common. The conformation of the knee (or stifle joint) is abnormal and related to breeding and genetic predisposition. We see dogs with a curved distal femur and proximal tibia which positions the tibial crest, and the insertion point of the patellar ligament, towards the inside of the stifle. This leads to patellar instability and a gradual shallowing of the femoral trochlear groove, in which the kneecap is normally seated. This creates an unstable knee joint that is more prone to arthritis and degeneration with age.

- Traumatic Medial Patella Luxation. This is a rare occurrence and is associated with severe soft tissue and ligament damage.

Signs of patella luxation injury in dogs

The first sign you’re likely to see in your dog is a sudden onset of lameness in a hind leg. This will result in the dog intermittently holding the leg up and walking around without putting any weight on it. Often dogs will “skip” when running. You may also notice your dog shaking or extending the leg prior to the limp subsiding.

How are dogs with patella luxation treated?

If the dog is experiencing these issues, the kneecap will remain unstable. Surgery is likely to be the recommended option in cases with clinical lameness. Generally medical treatment (such as anti-inflammatories) are used, however, longer term the bio-mechanical underlying cause has to be addressed with a corrective surgical procedure.

What happens if surgery on your dog is not performed?

As the pet ages the trochlear groove become shallower (the trochlear groove is prone to this if the patella is not properly in position) and the patella is likely to remain permanently luxated. Clinically the animal may walk relatively normally, however, arthritis will develop and the patient is unable to fully exert the force of the quadriceps muscle to the tibia and gait and strength are affected. As it is an unstable structure, the dog could also be prone to cruciate ligament injury.

What is Sydney Animals Hospitals approach to patella luxation injury?

Surgical repair has a good prognosis and low complication rate. Once the patient has completed a four-week post-operative rest period we usually see a return to proper function.

Why is your dogs knee prone to injury?

The knee (stifle joint) is stabilised by ligamentous and fibrous structures. Other joints, such as the elbow and hip have interlocking articular surfaces. The stifle anatomy relies upon the cruciate ligament, the patella ligament, collaterals and the menisci as well as muscular structures to achieve stability and movement.

Patellar luxation is one of the most prevalent knee joint abnormalities in dogs. The condition is most common in toy and miniature dog breeds (terriers, poodles, spaniels, Chihuahuas and their crosses are particularly highly represented). These small dogs are thought to be 12 times more likely to exhibit patella luxation.

Summary

  • Larger breeds have less genetic predisposition to problems with the kneecap. They typically have a deeper trochlear groove.
  • In young dogs the patella can pop out and back in without any pain, however this may change with age.
  • There are certain breeds that have a predisposition to a luxating patella.
  • Most pets are genetically predisposed to the condition but occasionally it can be caused by trauma.

Contact Sydney Animal Hospitals for veterinary advice on treatment of your dog for patella luxation injury.

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