Last Updated: 07/05/2025
Has your dog been diagnosed with luxating patellas? Find out all about the causes diagnosis and treatment in our comprehensive vet guide.
Author: Dr Gillian Hill BVSc (Hons)
Reading Time: 9 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.
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. It can occur medially (moves toward the midline of the body or towards the other leg - which is the most common) or laterally (moves towards the outside/away from the other leg).
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.
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.
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.
Symptoms associated with a grade 2 luxation are usually 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.
With grade 3 and 4 luxations, the 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
Lameness or limping which worsens after strenuous exercise
Appearing to have stiff joints, especially after rest
Slow to rise from sitting or lying
Reluctance to use stairs or jump into the car
Avoiding sitting or lying on hard surfaces
Loss of muscle mass in the rear legs
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.
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 lucations should be treated surgically.
Medical management for patellar luxation is aimed at delaying the onset, or severity, of arthritis in the joint.
There are a number of natural extracts and herbal products with proven anti-inflammatory properties. Some are antioxidants, which slow the actual progression of arthritis, while others intercept the inflammatory cascade to limit pain and inflammation.
Green Lipped Mussel for dogs contains key omega-3 polyunsaturated fatty acids, glycosaminoglycans (a source of chondroitin), vitamins and minerals which have been shown to have beneficial anti-inflammatory effects in dogs with arthritis. Similar to other joint supplements, it may take several weeks to notice visible effects, however it has been shown to play a role in reducing inflammation and pain in the joints.
Glucosamine for dogs and Chondroitin are the building blocks of normal healthy cartilage. Despite a lack of strong evidence in the veterinary literature, some veterinarians and owners have found supplementation to be helpful. With minimal side effects compared to some of the common pain relief medications, they are a good option for mild cases and to use alongside other therapies.
Omega 3 fatty acids DHA and EPA have been demonstrated to have anti inflammatory properties, and as far as supplements for arthritis go, they are backed by the most convincing evidence. Omega 3's can be obtained from lots of difference sources including fish oil, green lipped mussel powder, flaxseeds and nuts. Marine sources of omega fatty acids (such as fish, fish oil and green lipped mussel) are the most effective for dogs.
Your veterinarian will determine the most appropriate pain relief regime for your dog. Common medications for pain relief include non-steroidal anti-inflammatories like Firocoxib ('Previcox') and Meloxicam ('Metacam'), as well as opioids and gabapentin. In some cases, multiple medications may be recommended to achieve the best results. Some forms of pain relief aren't suitable for some dogs due to concurrent health issues, so every case is assessed on an individual basis.
For more information about the types of pain relief used for arthritis, take a look at the Best Arthritis Medications for Dogs.
Your vet may also prescribe a course of injections to help manage arthritis. The brand name of these injections can vary (Zydax, Cartrophen, Pentosan), however the the active ingredient, Pentosan Polysulfate, is the same. Pentosan polysulfate is of plant origin and acts within the joint to preserve joint health and provide pain relief. It is usually given as a series of injections, one injection per week for 4-6 weeks, followed by a booster injection at a time frame specificed by your vet.
Weight control is the single most important strategy in the management of arthritis in dogs. Extra weight results in increased stress on the joints and also makes dogs less likely to move around. Fat cells also release inflammatory mediators which can contribute to inflammation and pain in the body.
Just like for humans, weight control relies on diet and exercise. There are numerous low-calorie diets available in both wet and dry varieties - and even special diets with joint care ingredients.
Looking for more ideas? Read our article on Tips to Help Your Dog Lose Weight.
When it comes to exercise, balance is key. It is important to not overdo it and cause excessive luxation of the patella, which can lead to discomfort and accelerated cartilage destruction. Low impact exercise options such as swimming or hydrotherapy can be great for dogs with luxating patellas or those that suffer from arthritis.
Environmental enrichment is a great way to get your dog moving without overstressing the joints and provides them with important emotional enrichment also.There is a range of interactive dog toys and puzzle feeding toys available to encourage activity and keep your dog entertained.
Looking for more ideas? Read our article on Boredom Busters For Dogs.
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 - in this technique, 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.
Want to know more? Check out our Discover Page for more tips from our expert vets on keeping your pets happy and healthy.
