Luxating Patella In Dogs

What is a Luxating Patella?

The patella is also known as the kneecap. A groove at the end of the femur called the femoral groove allows the patella to move up and down when the knee joint is bent back and forth. The patella is also responsible for guiding the movement of the quadriceps muscle and protecting the knee joint.

For some dogs, the patellar groove’s ridges are not prominent enough to allow for normal movements because of malformation of this groove or trauma to the knee. In dogs with patellar grooves that are too shallow, the patella will luxate (jump out of the groove) sideways, often to the inside; this is called a medially luxating patella.

What Caused My Dog to Have Luxating Patellas?

Luxating patellas are very common in small-breed dogs. This prevalence in smaller breeds is due to years of selective breeding, shrinking their ancestors’ large skeletal structure down to the size of breeds we have today, such as Pomeranians, Shih Tzu’s, and chihuahuas. This decrease in size comes with changes in the shapes of bones, such as the ones involved in the kneecap’s proper functioning. However, larger breeds can also experience luxating patellas. Obesity can also contribute to the condition.

If left uncorrected, the patellar ridges can wear down, and the groove may become even more shallow. As this happens, the frequency and severity of lameness will also increase. Arthritis may prematurely affect the joint, causing swelling and impaired mobility. Early diagnosis and treatment are important to prevent the development of complications with the joint.

How Will I Know If My Pet Has A Luxating Patella?

Most dogs who are diagnosed with luxating patellas show signs of this condition. Symptoms of a luxating patella include:

  • Intermittent lameness, especially in the hind end.
  • Abruptly stopping and crying out in pain when they are running; this may be followed by sudden lameness.
  • Abnormal hind limb movement, such as skipping


At your pet’s annual Physical, your veterinarian will do a complete exam on your dog. This includes an orthopedic exam where we will assess the stability of your dog’s knees. Luxating patellas are graded on a scale from I to IV, where Grade IV is the most advanced. The distinctions between each level are:

No Patellar Luxation Present – The dog’s patella is stable and cannot be manually moved out of the patellar groove.

Grade I – When manual pressure is applied, the dog’s patella does move out of the patellar groove but returns to its normal position as soon as pressure is released. At this grade, the patella does not jump out of place on its own.

Grade II – The patella can be moved manually and may occasionally jump out of place when the dog is walking or running. The patella will return to its normal position spontaneously or with the application of pressure, moving it back.

Grade III – The patella is out of the grooves the majority of the time. It can be manually pushed back into place but quickly jumps out of the grooves as soon as the leg is moved.

Grade IV – The patella is always out of position and cannot be manually pushed back into the correct position. The grooves that are supposed to keep the kneecap in place are worn down and, in some cases, absent.

Treatment Options

Three common surgeries correct luxating patellas – Trochlear Modification Surgery, Lateral Imbrication Surgery, and Tibial Crest Transposition Surgery.

Trochlear Modification Surgery involves deepening the groove at the base of the femur the upper bone in the joint) to better guide the knee cap.

Lateral Imbrication Surgery approaches stabilizing the patella by “tying it down” on the outside of the knee to prevent it from slipping inwards.

Tibial Crest Transposition Surgery involves surgically changing the shape of the tibia to improve the patella’s movement.

All of these procedures work well, and the type performed depends on the individual case and the clinician. Depending on the procedure, dogs typically respond quickly after surgery and are usually completely recovered after 30-60 days of rest.

If you suspect your dog has a luxating patella, please call our Veterinary Hospital and schedule an appointment with one of our veterinarians who will evaluate your pet and discuss the next steps needed to get your best friend the proper treatment.


Carolyn Schew
Technician at Rittenhouse Location