Floating Kneecaps

Description of a Luxating Patella or ‘Floating Kneecap’

The kneecap sits in the same place in dogs and humans – at the distal end of the femur. It helps the quadriceps muscles flow across the joint between the thigh and lower leg so your dog has mobility and use of her shin.

The kneecap moves up and down in a groove. Patella ridges hold the kneecap in place, and as long as the ridges are deep (picture a pea in a peapod), the kneecap can only move up and down as nature intended.

Unfortunately, some dog breeds have a very flat patella ridge. This means the kneecap doesn’t seat snugly in the groove and it can pop out either medially, to the inside, or laterally, to the outside. Typically in larger dogs, the kneecap pops laterally, while smaller dogs’ kneecaps tend to pop to the inside.

Size and Breed Matters
A genetic predisposition to luxating patellas occurs in a variety of small and tiny dogs, including:

  • Miniature and toy Poodles
  • Maltese
  • Jack Russell Terriers
  • Yorkies
  • Pomeranians
  • Pekingese
  • Chihuahuas
  • Papillions
  • Boston Terriers

Short-legged dogs, for example Basset Hounds and Doxies, aren’t genetically prone to the condition. However, because their femurs are so short, it can change the angle of the seating of the kneecap, and these dogs can end up with luxating patellas as well.

Larger breeds have less genetic predisposition to problems with the kneecap. They typically have a nice, deep groove for the patella to seat in.

However, larger dogs are prone to hip problems. If a joint above the kneecap like the hip joint, or one below the kneecap like the ankle develops a problem, it can change the ergonomics of the animal’s body. If there’s a problem with your dog’s hip, it can cause a kind of ripple effect that forces the patella out of its groove.

Large and giant breed dogs with hip dysplasia often have a secondary condition of luxating patella which is caused by the malformation of the hip joint.

Kitties can also develop floating kneecaps, however, the situation is usually much less clinically severe.

Cats are smaller and lighter in body weight than most dogs. They are also more flexible and their bodies move differently. A 10 pound cat with a significant kneecap issue often won’t show many or any clinical symptoms such as limping.

Severity of the Condition

There are four levels of severity of a luxating patella. Grade 1 is the mildest; Grade 4 is the most severe.

  • Grade 1 luxating patella describes a kneecap that pops out (or can be manually popped out of place), but pops right back in on its own.
  • Grade 2 describes a kneecap that pops out of place and doesn’t always pop back in automatically, sometimes requiring manual manipulation to re-seat it.
  • Grade 3 condition is when the kneecap sits outside its groove most of the time, but can be manually positioned back in the groove, where it stays temporarily.
  • Grade 4 luxating patella describes the worst-case scenario, in which the kneecap sits outside the groove all the time, and won’t stay seated in the groove when it is manually popped into place.

You can see by these levels of severity why a displaced kneecap can cause intense pain for the animal.

Often in young dogs with strong, resilient joint cartilage, the patella can pop out and back in without obvious signs of pain. There may be an intense jolt of pain as the kneecap moves across the patella ridge, but it’s gone in a flash and usually not obvious to an observer.

The dog won’t want to put weight on his leg until the kneecap has popped back in (which can cause another flash of pain), but otherwise he appears fine.

Ultimately, however, as the cartilage wears down from the frequent travel of the kneecap in and out of its groove, there will be bone-to-bone contact and the condition can become acutely painful for your pup.

Diagnosis and Treatment

If your veterinarian diagnoses even a mild Grade 1 luxating patella in your pet, I recommend you address it right away.

Taking a proactive approach to treating the condition — no matter how mild, and especially in a young dog — can often prevent future surgery, joint degeneration, and diminished quality of life.

  • The first thing you should do for a dog diagnosed with a floating kneecap is help him achieve and maintain a healthy body weight. It’s just common sense that the heavier the dog, the more burden there will be on his knees.Optimal body weight for your dog means lots of lean muscle and a reduced amount of fat. This condition will limit stress on the joints.
  • Number two, it’s very important to keep your pet moving. Maintaining excellent muscle tone will help your dog’s body form a kind of cage around the knee which will keep the patella in place.Years ago, veterinarians advised owners of dogs with floating kneecaps to prevent their pets from moving around. We now know that’s a really bad idea. The more toned the muscles of your dog’s legs are, the more stable the kneecap will be. Building muscle is an extremely important part of reducing the clinical symptoms of a luxating patella.
  • The third action you should take is to provide your pet with oral joint support supplementation in the form of glycosaminoglycans, or GAGs. There are GAGs on the market specifically for veterinary use. However in my practice, we use several human oral joint support supplements to help maintain the integrity of knee cartilage while also improving joint fluid production.I recommend you discuss the subject with your integrative or holistic vet, who will be able to suggest or provide the right supplements to rebuild and maintain strong and resilient cartilage and joint fluid production in your dog.
  • I suggest you also discuss Adequan, an injectible joint support supplement with your vet. Adequan helps dogs that are developing premature arthritis. It slows down joint degeneration and improves joint fluid production.
  • Chiropractic and acupuncture treatments are also great modalities for dogs with luxating patella. Especially if you have a puppy with the condition, there are some very effective chiropractic manipulations that can be performed to keep the hips and knees in good alignment. This will in turn help prevent progression of the condition.
  • In addition to daily aerobic exercise to maintain your dog’s physical conditioning, I recommend you feed a species-appropriate diet. All foods are categorized as either pro or anti-inflammatory. By feeding your dog an anti-inflammatory diet (one very low in carbohydrate content), you can help reduce or moderate the effects of inflammation in your pet’s body, including the joints. Feeding a species-appropriate, carb-free diet can significantly reduce the inflammation associated with a luxating patella.


When to Seek Surgery for Your Pet

Traditional veterinarians often recommend surgery upon diagnosis of a luxating patella, regardless of the severity of the condition.

I’m not a proponent of surgery for a floating kneecap unless the condition is destroying your dog’s quality of life. If your pup can’t walk or run without intense pain, you should consider surgical correction.

There are two main goals of corrective surgery for a Grade 3 or 4 luxating patella.

One method is to deepen the trochlear wedge. If the joints are flat, the veterinary orthopedic surgeon will cut a deeper V to help hold the kneecap in the groove.

The other goal of surgery is to moderate the amount of tension in the patella capsule or ligament by tightening down the joint capsule.

My recommendation is to explore all possible non-surgical options to help stabilize your dog’s knee before you consider surgical correction. Surgery for this condition carries the usual risks associated with anesthesia and infection, plus a few more because the correction is to a moving part of your pet’s body that is also weight bearing.

These risks include:

  • Problems with a pin. If a pin is inserted to hold the joint in place it can migrate, requiring surgery to remove it. Also an abscess, called a seroma, can form at the site of the pin and require either draining or surgical removal.
  • Repair collapse. Post surgery, your dog should not run or jump for about two months to allow the repair to stabilize. This is a tough order for most healthy dogs, and it’s not uncommon for the repair in an active dog to break down during this period.
  • Failed surgery. Around 10 percent of dogs do not show significant improvement after surgery. They continue to experience pain. In addition, sometimes repair of the kneecap can cause problems to develop in other bones and joints.