Last Updated: 28/10/2025
Luxating Patellas in Dogs: a Vet's Guide to 'Floating Kneecaps'
Does your dog 'skip' or limp? It could be a luxating patella ('floating kneecap'). Our vet guide covers the causes, symptoms by grade, diagnosis, and treatment, from joint supplements to surgery, to help your dog.
Author: Dr Gillian Hill BVSc (Hons)
Reading Time: 8 minutes - short read
Luxating patella, or "floating kneecap", is a common orthopedic condition that affects many dogs, particularly small and toy breeds. This condition occurs when the kneecap dislocates from its normal position, leading to discomfort, lameness, and potential long-term joint issues.
Understanding the causes, symptoms, and treatment options for luxating patella is crucial for dog owners, especially those with breeds prone to this condition. In this article, we will delve into the intricacies of luxating patellas in dogs, providing insights from veterinary experts to help you better care for your canine companion.
What is a luxating patella?
A luxating patella is a knee cap which dislocates, or 'luxates' - it pops sideways, out of place from the groove in the bottom of the femur bone that it normally sits in.
The luxation can occur:
- Medially: the patella moves toward the midline of the body or towards the other leg. This is the most common scenario.
- Laterally: the patella moves towards the outside/away from the other leg.
The grades of luxating patella
Luxating patellas are graded depending on severity:
Grade 1:
- The patella can be luxated, but spontaneous luxation of the patella during normal joint motion rarely occurs.
- Generally dogs with a grade 1 luxation show no lameness, and the diagnosis is made as an incidental finding on physical exam.
Grade 2:
- The patella luxates occasionally with flexion and extension of the joint, but reduces spontaneously.
- Dogs with grade 2 luxations may sometimes 'skip' when walking or running, caused by the leg being unable to extend when the patella is luxated.
Grade 3:
- The patella luxates consistently, however the person examining can reduce it back into the groove.
- It is classed more as a mechanical lameness as the joint is often abnormally positioned and the hind legs may have a bow-legged and/or pigeon-toed appearance if there is a medial luxation.
- If it's a lateral patellar luxation - then the legs may have a knock knee'd appearance.
- Dogs with a grade 3 luxating patella may crouch in their back legs while walking.
Grade 4:
- The patella is consistently luxated and is unable to be reduced back into place.
- This causes the dog to walk with a crouched appearance as his knees are bent consistently.
- This limb is readily seen as abnormal, as seen in Grade 3.
While the luxation itself is not painful, the sliding of the patella in and out of the groove damages the lubricating cartilage and flattens the groove which can lead to osteoarthritis, or arthritis, reduced mobility and limb changes.
What causes luxating patellas in dogs?
Luxating patellas are usually a developmental disease with the onset occurring during growth.
Risk factors for the development of luxating patellas include:
- Mal-alignment of the quadriceps muscle - the quadriceps tendon attaches to the patella and can pull it out of it's proper alignment.
- Bowing of the bottom part of the femur.
- Deformity of the tibia.
- Mal-alignment of the hip joint, often from hip dysplasia, which can cause the line of force of the quadriceps muscle to shift.
- Trauma to the bone or soft tissues of the back leg, or contraction of muscles caused by nerve changes.
- Instability of the knee joint, such as from previous surgery or injury to the cranial cruciate ligament.
Breeds prone to luxating patellas
Luxating patellas can occur in both sexes in any breed of dog (and cat), but mostly occurs in toy and miniature breeds.
Large breeds, such as Newfoundlands, have a higher percentage of lateral patella luxations compared to small breed dogs.
Patellar luxation has been shown to be heritable in toy spaniels and toy and miniature poodles.
Signs and symptoms of luxating patellas
The signs and symptoms of luxating patellas will vary depending on the grade of luxation.
Grade 1:
- Generally no noticeable symptoms, and the diagnosis is made as an incidental finding on physical examination
Grade 2:
- Occasional skipping in the affected back leg. The dog will flex the limb and hold it up for a few steps and then walk normally again
- Occasionally, the tissues around the knee joint will become stretched and lead to lameness where the dog will not bear weight on the affected leg
- Over time, a grade 2 luxation can progess to a grade 3 luxation through the flattening of the groove, and can also lead to arthritis in the joint
Grade 3 and 4:
Symptoms tend to be more constant. These include:
- Constant limp in the affected leg or legs
- Walking in a crouched or slanted position in the back legs
- An unusual shape or angle to their hind legs
- Reluctance to jump
More severe luxations will lead to arthritis in the knee joint. Read more about Arthritis in Dogs.
How is a luxating patella diagnosed?
The diagnosis of patellar luxation is usually made on the basis of the symptoms and physical examination. Xrays are usually performed if surgery is planned as they can pick up other associated disorders such as cranial cruciate ligament tears and concurrent osteoarthritis.
Treatment for luxating patellas
The treatment for patellar luxation will once again depend on the grade of the luxation.
Grade 1 luxations are managed conservatively with medical management.
Grade 2 luxations may be treated medically, or surgery may be warranted based on the frequency of luxation and/or the level of lameness, or to prevent the condition progressing to higher grades.
Grade 3 and 4 luxations should be treated surgically.
Medical and non-surgical management
Medical management for patellar luxation is aimed at delaying the onset, or severity, of arthritis in the joint.
Surgical Treatment for Luxating Patellas
Surgery is indicated for grade 3 and 4 luxating patellas, and also grade 2 depending on the dog's age, clinical signs and likelihood of the luxation progression to higher grades.
A number of different techniques have been developed with the aim to secure the patella within the trochlear groove. Usually, a number of different techniques are used for best results.
Trochlear Resection
The trochlear groove which the patella should sit within, is deepened, to help prevent the patella from slipping out.
Lateral Reinforcement
For medially luxating patellas, the tissues on the outside, or lateral side, of the knee joint are reinforced in a number of different ways, to help pull the patella laterally and help it to remain in the groove.
Tibial Crest Transposition
The top of the tibial bone where the quadriceps muscle attaches is removed and replaced in order to realign the mechanical forces of the quadriceps muscle.
Ridgestop Implant
This is a new technique which involves the addition of an implant to the inside edge of the trochlear groove, to prevent the patella from slipping out.
Most dogs make an excellent recovery and return to normal limb function following surgery. However, if there are other concurrent abnormalities, such as limb deformities, hip dysplasia or cruciate ligament injury, the prognosis may not be as good.
Luxating patella, or 'floating kneecap', is a common diagnosis, particularly for smaller dog breeds. While it can sound worrying, it is a manageable condition.
With a clear diagnosis and a grading of the severity, a vet can recommend the best path forward. Many dogs are managed well with non-surgical options like weight control and joint support, while others benefit greatly from corrective surgery. Most dogs go on to live comfortable, happy lives.
If you notice your dog 'skipping' or showing signs of lameness, speak to your vet about the next steps.
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