Has this ever happened to you? You’re out enjoying a nice walk with your dog, when suddenly she yelps, lifts one of her back legs completely up off the ground, and immediately appears lame. Panicked, you try to figure out what in the world is going on while she spins around whimpering, and then suddenly… she puts her foot back down and starts walking again like nothing ever happened.

Chances are, you’ve just witnessed a classic Luxating Patella.

Luxating Patella goes by many different names: “floating kneecap”, “trick knee”, and “slipped kneecap”, to name a few. Essentially, they are all terms for the same condition, which is a temporarily dislocated kneecap (“luxating” means “out of place”, and patella is the medical term for kneecap).

This condition is extremely common in small and toy breed dogs, and when it happens, it can be quite painful. Luxating patella is one of the most common orthopedic conditions seen by veterinarians, and it’s most commonly diagnosed in puppies around 4 months of age (although any dog, regardless of age or breed, can develop it).

But in order to understand what causes luxating patella, you first need to know a little bit about how the knee works – and what happens when it doesn’t work the way it should.

Anatomy Of A Knee

Dogs’ hind (back) legs are very similar to our legs. They’re made up of the thigh bone (femur), the shin bones (tibia and fibula), and the knee joint that connects these bones together. Sitting on the front of the knee joint and held in place by ligaments and tendons is a little round bone called the patella (kneecap).

In normal knees, the patella fits very nicely in a notched area at the bottom of the femur called the patellar groove. The patella’s job is to protect the knee joint (and judging by how often we bang our own kneecaps, it does that job very well!). As the leg bends, the patella slides up and down within the patellar groove to give the joint maximum flexibility, and the groove helps to keep the kneecap in place.

Unfortunately, some dogs have a patellar groove that isn’t deep enough to hold in the knee in its proper position. In a dog with luxating patella, the kneecap temporarily slips out of the patellar groove and moves off to either side. The sensation the dog feels when this happens causes the dog to stop and pull its leg up off the ground until the kneecap can pop back into position.

Luxating patella can also occur as the result of trauma. This can be something as serious as being hit by a car, or something as innocent as jumping off a couch or bed and landing the wrong way on the floor. However, it’s much more likely to be due to a patellar groove that’s just too shallow.

Regardless of the cause, luxating patella needs to be treated. If it keeps occurring, arthritis will eventually develop in the joint, causing permanent damage and a great deal of pain and loss of mobility for the dog.

Breeds Predisposed To Luxating Patella

Although any dog can develop luxating patella, it’s much more common in toy breeds, including:

• Toy and Miniature Poodles
• Pomeranians
• Chihuahuas
• Papillons
• Jack Russell Terriers
• Malteses
• Yorkshire Terriers
• Pekingeses
• Boston Terriers
• Bichon Frises

Some dogs with very short legs, like Dachshunds and Basset Hounds, can also develop luxating patella because their short femur bones throw off the angle of the patellar groove.

Symptoms Of Luxating Patella

The most obvious symptom of luxating patella is sudden apparent lameness in a back leg, followed by the dog either holding its leg up completely off the ground, or walking with a distinctive on-and-off “hop-skip” step.

The video below shows a dog walking with a luxated patella:

Other symptoms can include:

• Lameness in a back leg that seems to come and go for no apparent reason
• A bowlegged appearance when viewed from behind, particularly in puppies
• Shaking or extending the back leg after the patella pops out of place in an attempt to pop it back in
• Temporary paralysis of the knee joint
• Difficulty getting up from a reclining position
• Reluctance to run and jump
• Noticeable weakness in the affected leg
• Swelling around the knee joint

Diagnosing Luxating Patella

If you suspect that your dog has luxating patella, make an appointment with a veterinarian as soon as possible. The vet will take x-rays of the knee to view the position of the patella, as well as to assess whether the patellar groove of the femur is too shallow to hold the kneecap in place. The vet will also perform an examination of the knee by feeling the entire joint, which can help determine if the patella is sliding around more than it should be.

There are four levels, or grades, of severity with luxating patellas, with Grade 1 being the mildest and Grade 4 the most severe.

Grade 1: The dog is not usually in pain. The patella pops out (or can be manually popped out), but pops right back into place on its own.

Grade 2: The patella pops out of place but doesn’t always pop back in on its own; sometimes it requires manual manipulation to put it back into place, but usually moves out of place again when the dog starts walking. A dog with this grade is usually not painful, but if left untreated, the pain can progress and arthritis can develop.

Grade 3: Dogs in this stage are usually in pain and arthritic. The patella is sitting outside of the patellar groove more often than it is inside the groove. If it’s manually put back into place, it stays there temporarily, but then pops right back out.

Grade 4: The patella is outside the patellar groove all the time, and won’t stay there at all if manually put back into place. The dog is usually experiencing quite a bit of pain and already has degenerative damage to the joint.

Treating Luxating Patella

The goal of treatment for luxating patella is twofold: to relieve pain, and to improve the function and stability of the knee.

There are several non-surgical things you can do to help a dog with luxating patella:

• Make sure your dog is not overweight. Extra body weight will put a tremendous amount of pressure on an already-compromised knee joint. If your dog is overweight, talk with your veterinarian about safely modifying his diet to help him lose weight.
• Although it may sound counterintuitive, keep your dog moving! This will enable him to build up the muscles around the knee to help hold the patella in place.
• Give your dog joint supplements containing glucosamine and chondroitin, which are proven to improve the production of joint fluid (which helps cushion the knee joint) and help rebuild damaged cartilage.
• Ask your vet about Adequan, an injectible joint support supplement that also helps repair cartilage and increases joint fluid production.
• Consider adding Omega 3 fatty acid supplements to your dog’s diet. Omega 3 fatty acids can have an anti-inflammatory effect in joints. High-quality fish oils are a good source of Omega 3’s; ask your veterinarian for recommendations.
• Consider other non-traditional treatments, such as acupuncture, hydrotherapy (swimming and special exercises done underwater to strengthen the knee), massage therapy to stimulate healing and reduce stress, and acupressure to increase circulation.

Although all of the above suggestions will certainly help a dog with luxating patella, here’s the thing: non-surgical methods will never be able to change the anatomy of your dog’s leg. For this reason, surgery is by far the most recommended approach to correcting a luxating patella.

Why Surgery Is Almost Always The Best Option

Unless a dog is older and/or has other serious medical conditions that make him a poor candidate for anesthesia, surgery for luxating patella remains the most effective way to repair and correct the issue.

The procedure is very straightforward: in most cases, a veterinary surgeon uses orthopedic tools to scrape out and deepen the patellar groove so the kneecap no longer slips out of place. In more serious cases, some surgeons will also surgically alter the position of the ligament that holds the patella in place and tighten the joint capsule of the knee to make it more stable.

After surgery, most dogs recover very quickly. The affected leg is bandaged for a few weeks, then once sutures are removed, the dog is able to start going on short walks to build up strength in the repaired leg. The success rate for this surgery is approximately 90%, with little to no recurrence of the issue.

Why No Dog Should Live With A Luxating Patella

Luxating patella in any dog should ALWAYS be treated. Left untreated, the movement of the patella back and forth in and out of the patellar groove will wear down the cartilage in the knee and eventually cause bone-on-bone contact, which can be extremely painful and cause permanent damage to the joint.

Diagnosing and treating luxating patella early can help prevent arthritis and loss of mobility, and can greatly improve a dog’s quality of life. If you suspect your dog has luxating patella, be sure to schedule an appointment with your veterinarian. Your dog will thank you!

Have you ever had a dog with luxating patella? Please tell us about it in the comments below!

¹ Photo Credit: Wikimedia Commons: Radiograph of patellar luxation

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