What Is a Luxating Patella in Dogs and How Do I Prevent It?
What Is a Luxating Patella?
The patella is another name for the kneecap, which is a thick, triangular-shaped bone that protects the knee joint. In a dog with normal knees, the patella sits in a groove and rides up and down as the leg bends and stretches. In a dog with a luxating patella (sometimes referred to as 'trick knee'), the kneecap is prone to slipping in the groove and may even completely pop out of place.
How Serious Is It?
There are four grades of patellar luxations, and most dogs suffer from grade 1 or 2. In severe cases (grade 3 or 4), the patella slips out permanently and causes a dog to walk with inward-bent legs or prevents the dog from using the affected leg entirely.
Patellar Luxation Grades
The knee can be manually moved out of its groove upon veterinary examination but pops back in by itself.
If caught early, can be treated with physiotherapy and hydrotherapy to build up muscle to hold the knee in place.
The knee can be manually moved out of its groove or will spontaneously pop out as the leg is manipulated. It does not immediately pop back into place and must either be pushed back into place or popped back in by stretching the dog's leg.
If caught early, can be treated with physiotherapy and hydrotherapy to build up muscle to hold the knee in place. If the condition is not treated, the knee will deteriorate and ultimately, surgery will be required.
The kneecap spends most of the time out of its groove but can be manually pushed back in. Any stretching or bending of the dog's leg causes the knee to pop out.
Requires surgery to improve the groove of the knee and to realign the tendons that attach it.
The kneecap is permanently out of its groove and cannot be replaced with manual manipulation. The groove is so shallow that the patella has nothing to sit in.
Requires surgery to improve the groove of the knee and to realign the tendons that attach it.
Complications That Can Arise If Left Untreated
Fortunately, grades 3 and 4 are unusual, but the constant slipping of the knee, even in low-grade luxations, places great strain on the joint and can lead to further injury.
Cruciate Ligament Rupture
The cruciate ligament can rupture when the knee is out of position. Why? The cruciate ligament stabilises the knee and prevents over-rotation of the joint, but when the kneecap has slipped, extra pressure is placed on the cruciate causing tears or complete ruptures. This often requires surgery. In canine athletes, it can be a career-ending injury.
Another common complication of patellar luxations is arthritis in the knee from the constant wear and tear. Though dogs initially show no signs of pain, eventually they begin to experience discomfort and may find it painful to move about or walk.
Which Breeds Are Prone to Luxating Patellas?
Patellar luxations can be found in all types of dog, though they are commonly associated with smaller breeds. Some breeds are considered predisposed to the condition. In larger breeds, this condition is most often seen in labradors and is possibly linked to the high levels of hip dysplasia also reported in these breeds.
Small Breeds Predisposed to Patellar Luxations
Toy and Miniature Poodles
Small Mixed Breeds
A Classic Example of a Terrier With a Patellar Luxation
How Much Pain Does a Luxation Cause?
The answer to this question is complicated, as it depends on the grade of the problem and whether the animal has had treatment for the condition. Equally, dogs are very stoic and mask pain, so it can be hard to tell just what level of discomfort they are in.
In grade 1, the kneecap slips in the groove but does not necessarily pop completely out. This slipping does not initially cause pain, as the knee is cushioned with cartilage (which has no nerve endings). However, every time the patella slips, it scrapes away a tiny piece of cartilage. Over time, it wears it away completely and then the kneecap rubs against the underlying bone. At this stage, the problem becomes incredibly painful, and the dog will limp and may even refuse to place the affected leg on the ground. Any movement of the knee hurts, and the only recourse at this stage is surgery and pain management.
In grade 2, the kneecap will spontaneously pop, causing severe pain until it is replaced. In humans who have experienced this condition, they have described the popping of the knee as 'agony'. The first time the knee pops, it will be difficult to replace. With each subsequent displacement, the tendons loosen, and while this means the knee pops back quicker, in turn, this makes it easier for it to come out again. Ultimately, every time the knee pops, damage is being done to the knee joint, leading to further issues.
Grade 3 and 4
In grade 3 and 4, the knee is rarely in the groove. This condition is often noticeable from birth and causes a puppy to struggle to use its back legs. How much pain this causes the dog is difficult to determine, however, the unnatural position of the knee puts pressure on the bones of the leg and spine and also the other ligaments in the joint. The affected dog is likely in constant pain but has learned to adapt due to the problem being present from birth.
Any Luxation Left Untreated May Lead to Arthritis
Even with grade 1 luxations, if nothing is done to stop the knee from slipping, then arthritis will eventually form in the knees. Arthritis cannot be cured and will require long-term pain management. With all grades, there can be issues with pain in the lower back or in the leg muscles, including a condition similar to sciatica in humans due to the abnormal strain being placed on the joints.
A Dog With a Grade 3 Patellar Luxation
How Do I Know If My Dog Has a Luxating Patella?
Grade 3 and 4 luxations are typically obvious from birth as the dog will not be able to walk normally on its back legs. With grade 4, the problem is so severe that the puppy may struggle to learn to walk at all and the hind legs will bow (with the paws touching). In grade 3, the dog walks but has a strange gait—sometimes stumbling or appearing to be unbalanced. The problem will worsen rapidly. The dog may sturggle to climb up stairs or may turn in its back legs on a walk.
The signs of grade 1 and 2 luxations are much more subtle and the owner may not realise there is a problem until the dog is older and secondary issues, such as arthritis, have developed. Here are the telltale signs your dog suffers from grade 1 or 2:
Usually, the first sign of a luxating patella is skipping off of the back leg. A dog will be walking along in a trot or even running and miss pace with a hind leg. This can be rather obvious. The dog will actively pick up a hind leg, hop along a few paces without putting it down, and then begin to use it again. This is commonly seen in terriers and is often mistakenly called a breed trait when it is actually a sign of a slipping knee.
Clicking Sounds in the Joint
The slipping of the knee will cause you to hear a clicking sound when your dog straightens and bends its leg. You will often hear this when your dog rises from a sit to a stand. It sounds similar to a person cracking their knuckles.
Resistance to Having the Leg Manipulated
Dogs with luxations may find it painful for the leg to be stretched out, and this may become noticeable during grooming or if you stretch your dog before doing something like agility. The dog may tense the leg, whimper, cry out or even snap.
'Lazy Sits' or 'Puppy Sits'
A key sign of an issue with your dog is if they tend to flop into a 'lazy sit' or 'puppy sit'. This is a very loose sit with the hind paws either rolled under the body or the knees flopping out and the back paws touching. A normal sit should involve the dog sitting square on its haunches, the paws tucked in and the knees stacked over them. A lazy sit indicates discomfort. To learn more, check out my article on lazy sits.
Neck and Back Pain
As the issues with the dog's knees progress, the dog will begin to compensate and avoid using the affected leg. This means they will either carry all of their weight on their front end when running or jumping or will overuse the least affected hind leg. The result of carrying their weight in this unbalanced fashion is muscular strains. These may be seen in the lower back, hind legs, neck, shoulders and pectoral muscles. If the problem persists, the dog may present with a condition called 'dead tail', where their tail hangs down and cannot be wagged. Or they may develop sciatica pain. All of these conditions will improve if the luxation is corrected.
The main reason many dog owners take their pet to a vet and discover it has a patellar luxation is that the dog is chronically lame. The dog may limp constantly and dislike exercise, or it may hold a leg up. Stiffness and difficulty while moving from a sit or from being down are also classic signs that the condition has worsened and may indicate arthritis.
How Are They Treated?
Caught early, grades 1 and 2 can be treated without surgery. The key is to build up the muscles around the knee joint, especially the quads, in order to hold the knee in place and prevent it from slipping or popping. It will also be necessary to assist the repair of the knee joint using supplements.
There is a range of exercises that can be used to improve a dog's leg muscles, but they should be done under the supervision of a veterinary physiotherapist to ensure you are not doing greater harm to the joint, and to tailor the exercises to your dog's needs. Your vet should be able to refer you to a recognised physiotherapist. This should be considered for grades 1 and 2 before considering surgery.
Hydrotherapy, or water therapy, is one of the best ways to help a dog with a luxating patella. This should not be confused with just letting your dog swim as part of his walk. As with running, a dog may compensate for a sore leg when swimming by not using it. Going to a hydrotherapist will ensure that your dog is correctly using their body and getting the most benefit from this exercise.
There are a number of joint aids on the market for dogs and they are excellent for helping repair a damaged knee joint, along with the above therapies. You should choose one that contains high levels of glucosamine, chondroitin and MSM. Glucosamine and chondroitin have been scientifically proven to help the body rebuild cartilage, which is vital for a dog who has been wearing down the cartilage in his knees from a slipping patella. MSM is a natural anti-inflammatory and relieves joint pain.
Turmeric can reduce inflammation and is considered a natural antioxidant. It has been used as a traditional medicine for centuries. For your dog to benefit from turmeric, it can be fed twice daily in the form of a paste (follow dosing recommendations and use a dog-approved paste). It is also available to buy from pet suppliers.
For dogs with grade 3 or 4 luxations, surgery will be necessary at a young age. For dogs with grade 1 and 2, surgery will only become necessary if steps are not taken to treat the condition when it first presents. Surgery typically involves deepening the groove of the knee joint and realigning the tendons that hold the patella in place. Hydrotherapy and physiotherapy may be used afterwards to improve the muscle strength around the knee. Surgery is expensive, and it has the consequence of leaving your dog extremely prone to arthritis in its knees in the future.
Why You Should Intervene Early
Many owners put off taking their dogs in for physiotherapy or hydrotherapy because of the cost, however, this means that ultimately the dog will need surgery and long-term pain medication for arthritis. Patellar luxation surgery on a small dog can cost around £1,200 or more. In comparison, six months of physiotherapy could cost around £200-£300. Monthly hydrotherapy could cost between £120-£180 for six months.
Can I Prevent a Luxating Patella?
Many owners want to know how to prevent patellar luxations, but the condition is often genetic (conformity issues)—due to a defect in the way the hind limbs form—or injury-related. The only way to prevent it from occurring is for breeders to breed animals who have sound knees. This is not a complete guarantee that any puppy will be free of the condition, however, as genetics are complicated and there can be instances of the conformity issuing showing up in a line of dogs that has never before been affected.
If puppy buyers only bought from breeders who tested their dogs' knees, the problem would be greatly reduced and there would be far less risk of a dog developing the problem. This is especially important if you are buying a breed known to be affected by the condition, or you want to compete with your dog in a canine sport such as agility.
Responsible Breeding Will Reduce the Problem
If you are planning on breeding your dog, have his or her knees checked first. This is easily done by going to your vet and asking them to examine your pet. If the dog shows any signs of a knee issue, you should not breed them.
Tips for Preventing the Condition
If you already have your puppy or have a rescue dog with an unknown medical history, the best way to prevent knee problems is to treat them as if they have a grade 1 luxation. Do muscle exercises, such as asking them to go from a sit to a stand. Take them swimming and give them good joint supplements. Also, keep them at a healthy weight.
Though patellar luxations can be painful and frustrating, they are not life-threatening. With correct treatment, your dog will live happily and comfortably for many years without issue. Most dogs will not require surgery, and if problems are recognised soon enough, steps can be taken to ensure the problem does not worsen or result in arthritis. So, don't despair if your dog has been diagnosed with the condition, there is lots you can do for them to make them pain-free and able to enjoy running and playing for the rest of their lives.
Video: A Fun Hydrotherapy Demonstration
This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.