Out of the Groove

February 24, 2026

Luxating Patella in Cats

Nancy Kerr

Have you noticed your cat slowly experiencing increasing periods of lameness or favoring one of its legs? Or the sudden onset of these symptoms after experiencing a trauma? If so, your cat could have a what is known as a patellar luxation or luxating patella. “A patella is a kneecap, and ‘luxating’ means out of place or dislocated. So, a luxating patella is a kneecap that moves out of its normal location. The knee joint connects the femur (thighbone) and the tibia (shinbone). The patella is normally located in a groove (the trochlear groove) at the end of the femur, but with a luxating patella, it moves out of this position.”¹

“The extent to which a cat can crawl, walk, run, or leap depends on the structural soundness of its stifles, the joints in its rear legs. Each stifle houses the same components as those that constitute the human knee joint: the lower end of the thigh bone (femur); the upper end of the shin bone (tibia); and the upper end of a smaller bone (fibula), which is located adjacent to the tibia.”²

Causes

So how does a cat become a victim of a patellar luxation? This mostly occurs due to a congenital defect that develops as a kitten grows. While any breed can be affected “there may be a genetic predisposition to this problem in Devon Rex, Siamese, and Abyssinian cats.”¹ While common in small dogs, as often “the kneecap (patella) repeatedly or permanently dislocates without being injured, it is rare in cats, so these symptoms are more likely to be caused by a different issue.”³

Instead of remaining in place “the patella will luxate, or slip out of the groove, during extension of the leg if the trochlear groove is too shallow, if the cat is bowlegged or cow-hocked (i.e., the leg bones are excessively curved), or if the point of attachment on the tibia is off-center. Most of the time, in cats, the patella luxates because the trochlear groove is too shallow and the direction of luxation is towards the inside of the leg, which is called medial luxation.”¹ However, it’s possible for a kneecap to become dislocated due to physical trauma of the knee joint or leg, including the bones, patellar ligaments, and tendons. This can also include hind-leg trauma to the bones or muscles.

Making the Grade

When the kneecap is too loose due to patellar luxation, it is able to dislocate to varying degrees either side of the trochlear groove. This instability of the “knee leads to abnormal wear and tear on the soft tissue and bone within the joint, leading to inflammation of the knee and eventual arthritis.”³

A patellar luxation is graded on a scale of 1–4 based on what a veterinarian discovers while manipulating the kneecap during a physical exam. “The grades of luxation are: Grade 1: The patella can be luxated manually, but it does not dislocate on its own; Grade 2: The patella luxates spontaneously but, in general, stays in its normal position; Grade 3: The patella is permanently luxated but can be moved back into place; and Grade 4: The patella is permanently luxated and cannot be moved back into place. In general, the higher the grade, the more severe the clinical signs.”³

Symptoms

So how can you tell if your cat may have a luxating patella? If it was caused by physical trauma, the symptoms will suddenly become evident. If, on the other hand, the cause is a genetically inherited defect, the symptoms will have emerged slowly – gradually evolving into lameness as an affected cat grows older. However, not all individuals with luxating patellas will be lame. Gait development will sometimes be relatively normal and it will be only be discovered during an exam.

Symptoms can vary in type and severity depending on the progression of the condition:

“Cats with grade 1 patellar luxation typically show few to no symptoms, since their kneecap is in the right place most of the time. With grade 2 luxation, because the patella slips out of place on its own but goes back in easily and generally stays in place, the most common clinical sign is intermittent limping or refusal to bear weight on the affected leg(s). Most of the time, the cat walks normally and has only an occasional limp or carrying of one of their rear legs. This typically doesn’t appear to be painful and comes and goes with no apparent reason. With grades 3 and 4 luxation, the kneecap is out of place most or all of the time. As a result, signs of instability are more severe and persistent, such as persistent lameness. There may also be signs of arthritic changes to the knee joint, such as swelling, pain, or an abnormally large and knobby shape to the joint. A cat with a grade 3 or 4 patellar luxation won’t bear weight on the affected leg most or all of the time.”³

Common symptoms can be observed when the kneecap is dislocated, which include “limping or skipping on the affected leg, reduced activity level, hesitance or inability to jump or run and holding the rear limb at an odd angle. Other symptoms may include difficulty or inability to run or jump normally, spending less time in favorite high places, spending less time grooming, resulting in a poor coat condition, limping or skipping and signs of pain when certain areas of the body are touched.”³ With developmental patellar luxation, the cat usually does not appear to be in pain, so there is no apparent reason why it is suddenly carrying its rear leg. Then it returns to using the leg normally again. But cats who have a luxating patella due to a traumatic injury will often act as if they’re in pain and may have additional bodily injuries and symptoms.

Treatment

When a cat has a history of hind-limb limping, carrying a back leg, or other mobility issues, the veterinarian will usually start with a thorough physical exam. Based on what is found, X-rays of the affected leg may be recommended. Additional testing or advanced imaging may be necessary to rule other medical conditions in or out, or to better visualize the knee joint. The veterinarian will also test the kneecap to see if it can move. During this process you may hear some popping knee sounds, similar to people cracking their joints.

Treatment options depend on both the cat and the severity of the condition. Minor cases sometimes do well either without treatment or with conservative management, such as physical therapy, medication, and controlling physical activity. For severe cases, surgery may be required. If surgery is performed, “the objective will be to permanently restore the patella to its proper position in the femoral groove and adjust the tension of the tissues that are supposed to be holding the patella in place.”² “If both knees are affected, which is usually the case with the developmental form, the decision of whether to repair both knees at once or to separate the surgeries is made on a case-by-case basis.”³

Additional post-surgery treatments are usually recommended during recovery. These may include: prescription anti-inflammatories and pain relief, hot and cold compresses, maintaining a relaxed environment and minimal, controlled physical activity. It’s very important to restrict a cat’s exercise and/or activity while the knee is healing. It will be recommended to keep your cat indoors. If the cat is overly active, it may be necessary to confine in a crate to keep it from running or jumping on the knee as it heals, even if it seems to be feeling much better. Check with pet insurance to see if they will cover the treatment and/or surgery, since the cost can be several thousand dollars.

Prognosis

It is a good idea to check your home and reduce anything that may be a potential cause of trauma to a cat’s knees since this can happen from something as simple as losing its footing on a pile of loose papers. For cats with “grades one, two, and three luxating patellas, surgery is usually very successful, with little chance of recurrence. In cats with a grade four luxation, the chance of recurrence is approximately 50 percent.”³ The surgery is often not as successful as in dogs, however, so the decision to proceed should be based primarily on the function of the limb. If the cat is using the leg well, sometimes it is best left as is. The surgical procedure for correction is not an exact science, so the knee may still be loose afterwards or it may be overcorrected and become tight (limited movement). Wait a couple of weeks to see if things will correct themselves with time, rest, etc. Your cat may surprise you with its common sense in this matter.

Sources

1. Malcolm Weir, DVM, MSc, MPH; Tammy Hunter, DVM; Cheryl Yuill, DVM, MSc, CVH, Luxating Patella in Cats, 2025, Accessed 12/07/2025, https://vcahospitals.com/know-your-pet/luxating-patella-in-cats
2. Luxating Patella, Accessed 12/07/2025, https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/luxating-patella
3. How to treat luxating patella in cats, Dec 26 2024, Accessed 12/07/2025, https://vetster.com/en/wellness/how-to-treat-luxating-patella-in-cats