Luxating patella, also called “trick knee”, is a common orthopaedic problem in dogs where their knees spontaneously dislocate. A dislocating kneecap sounds and looks distressing, but our ever-resilient dogs have a habit of just carrying on, despite the discomfort they’re in.
There is no doubt this is a painful condition that can affect your pup’s quality of life, particularly when it comes to walkies. Here’s everything you need to know about luxating patella in dogs, including the causes, which dogs are affected, and how it’s treated.
Luxating patella is a common problem in dogs where your dog’s kneecap will dislocate and move out of place. The name describes the condition pretty well because “luxating” means moving, and “patella” is the proper name for a kneecap. Luxating patella will only affect your dog’s back legs, and it could happen in one or both legs.
It’s usually young dogs that are diagnosed with luxating patella, and your dog will probably show symptoms between the ages of 1 and 3 years old. However, luxating patella in older dogs isn’t impossible.
It’s estimated that 1.3% of the doggy population is affected by patella luxation, however there are high-risk breeds that are more predisposed to the condition. For example, 6.5% of Pomeranians develop luxating patella, which obviously means they’re far more at risk than the average percentage would imply.
Luxating patella is diagnosed and graded on a scale of severity, with grade 1 being the mildest and grade 4 being the most severe.
This is the mildest form and means your dog’s knee stays in place all of the time but it’s loose. At this stage, the kneecap will only pop out of place if it’s forced out of position. Dogs with grade 1 patella luxation rarely have symptoms and don’t usually require treatment.
This is slightly more severe and your dog’s kneecap will dislocate but will usually pop back into place on its own. Dislocation can happen rarely or regularly, so dogs suffering grade 2 luxation can show mild to moderate symptoms and pain.
Grade 3 means that your dog’s kneecap is dislocated out of place most or all of the time, and it won’t pop back into place on its own. Your vet will still be able to physically move the knee back into the correct position.
This is the most severe and it means your dog’s knee is permanently dislocated and cannot be moved back into the correct position on its own or by your vet.
There are three kinds of luxating patella in dogs, medial luxation, lateral luxation, and bidirectional.
Medial luxation means that when the dog’s kneecap dislocates it moves towards the inside of the leg, facing in. This is the most prevalent form of luxating patella in dogs, and it is more common in small breeds of dog.
Lateral luxation means that the kneecap dislocates and moves to the outer side of the leg, facing away from the body. Lateral luxation is uncommon and more often found in large and giant breeds of dog.
As you might guess from the name, bidirectional luxation means that the kneecap can dislocate and move in either the medial or lateral direction.
To understand what causes patella luxation, we have to look a little closer at how a healthy dog’s knee should work.
Usually, a dog’s kneecap sits inside a groove on the end of the femur called the trochlear groove, and the kneecap moves along this like a train on a railway track whenever your dog bends or straightens their leg. Just like a train on a track, this groove keeps your dog’s knee in place.
Below the knee is the patellar ligament, which is the strong connective tissue that connects your dog’s quadriceps to the tibia, or shin bone. It acts like a pulley that allows your dog to bend or straighten their knee.
Luxating patella is when the patella moves out of this groove on the front of the knee joint and drifts out of place to the side of the leg. This will also pull the ligament and the quadriceps out of place too. Sometimes it can be caused by trauma, but usually, a dog develops luxating patella due to an underlying weakness or abnormality in their leg.
For example, some dogs’ kneecaps are more likely to pop out of place because their trochlear groove is not as deep as it should be. Because the walls preventing the kneecap from moving are shallow, it makes it much easier for the patella to be pulled over the groove walls and out of place.
Your dog might also have a misaligned quadricep mechanism. If the pulley system of the quadriceps, knee, and patellar ligament don’t all connect in a straight line, then the kneecap can be pulled out of place following whatever path the mechanism follows. So if their mechanism goes in a diagonal across the front of their leg, their knee will be pulled diagonally too instead of straight up and down.
Dogs that suffer from hip problems, such as hip dysplasia, can develop luxating patella. Issues in one joint or area of a limb usually lead to some form of misalignment, which in turn can cause problems with other joints.
If your dog has torn their cruciate ligament, they might show signs of lameness similar to luxating patella. However, a torn ligament is a more serious problem that requires a different treatment.
Luxating patella can affect all dogs of any age, breed, gender, or size. However, it is more common in small and miniature breeds of dog.
Miniature and Toy Poodles.
Because Miniature and Toy Poodles are often affected by trick knee, their small crossbreeds can also be affected. That means pup-ular “doodle” breeds like Cockapoos and Cavapoos can be prone to luxating patella.
Other dogs with a bit of a “bow-legged” stance like the English Bulldog are also more likely to develop luxating patella due to the structure of their legs.
Dogs that are outside of the normal weight range for their breed are also more likely to develop luxating patella. Dogs who are below average weight have a slightly higher chance of being diagnosed with luxating patella. However, overweight and obese dogs are more likely to suffer from joint problems due to the additional pressure on the joint caused by their extra weight.
The most obvious side effect of luxating patella in dogs is lameness, and your pup’s ability to walk will be affected. They might not be keen to go for long walks or runs, and might avoid playing with other dogs. They might also have difficulty getting up and down the stairs. However, most dogs can still remain reasonably active until severe stages of the condition.
Dogs with luxating patella can go on to suffer from arthritis. When their knee pops out of place, it will rub against the cartilage at the end of the femur and wear it away, exposing the nerves in the bone beneath and causing pain and inflammation.
Having a misaligned and dislocating knee will also put strain on other areas of your dog’s limb. It will pull the quadricep and patellar ligament out of line, which is uncomfortable for your pooch. Luxating patella can also lead to damage in the cruciate ligament.
The main sign of luxating patella in dogs is hopping or skipping on walks.
If you’re out on walkies, your dog might be walking along perfectly fine then all of a sudden they’ll lift up one of their back legs and hop a few steps, before putting their foot back down and carrying on like nothing has happened. They also might just lift their leg up quickly and skip a step before putting the leg back down and carrying on as normal.
Otherwise, your dog might just show mild to severe stiffness in their back legs, particularly in their knees.
It can be hard to spot, but if you think your dog might have patella luxation, it’s important you take them to the vet for an examination. The earlier the condition is diagnosed and treated, the better your dog’s outlook of a full recovery. Treating luxating patella promptly will also lower your pooch’s chance of developing arthritis.
There isn’t a lot you can do to prevent luxating patella in dogs, especially when it is usually caused by a physical abnormality in your pooch’s leg that’s been there since birth. However, there are plenty of things you can do to improve the stability of your dog’s knee joint and to reduce their risks of joint problems.
Firstly, maintaining a healthy weight is crucial in keeping all of your dog’s joints healthy, including their knees. Not only does being underweight seem to increase the risk of luxating patella, but being overweight increases the risk of joint damage and arthritis and simply reducing your dog’s body weight significantly reduces signs of lameness.
Ensuring your dog eats a healthy diet, rich in protein and amino acids, will help to provide the nourishment they need to grow strong, healthy muscles. Having well-developed muscles with healthy function helps to strengthen and support other tissues in your dog’s leg. Providing plenty of antioxidants like vitamin C in their food will also help to reduce inflammation in their joints, which can help to make them more comfortable.
There should also be plenty of healthy fatty acids like omega-3 and omega-6 in your pooch’s food that will help to relieve inflammation in their joints and soothe symptoms of arthritis. These could be in their food or provided in a supplement. Chondroitin and glucosamine are also super effective in helping to alleviate joint pain and improve mobility in dogs.
A good diet and supplementation obviously can’t fix a physical abnormality like a misaligned knee. Although it can help to support your dog’s muscles and bones to strengthen their limbs, and it can help them to lose weight and reduce inflammation to improve your dog’s overall comfort and movement, allowing them to become more active and undergo physical therapy.
Plenty of regular exercise will also improve their muscle tone and strengthen the muscles and ligaments in their legs, which will in turn help to stabilise their joints by holding everything in place. Keeping fit also helps to prevent weight gain, so it’s important your dog keeps active! But if they are already suffering from luxating patella or another condition that impacts their mobility, make sure you always opt for gentle exercise under the advice of a vet.
If you want to improve your dog’s muscle tone and mobility under a watchful eye, you can find a pet physiotherapist. They’ll show you exercises and massage techniques to do with your dog that will work to strengthen their muscles and tissues, helping to improve their mobility and ease their symptoms. Sometimes, physical therapy is all that’s needed to treat a mild case of luxating patella.
If you suspect your dog has any problems with their limbs, or you’ve seen them “skipping” on walks, you should take them to the vet for an examination.
Your vet will perform a physical examination of your dog’s legs to check their range of motion and look for any abnormalities. If they suspect luxating patella, they will physically manipulate your dog’s knee to see if it is loose or able to pop out of place. They will also conduct x-rays to get an inside look of your dog’s leg so they can assess your dog’s bones and internal structure, allowing them to see any defects or damage to your pup’s knee that could be causing the problem.
Your pooch’s treatment will vary depending on the severity of their luxating patella and what’s causing the condition. If they don’t seem to be in pain and it isn’t impacting their daily activity, then you and the vet might choose to leave them as they are. Your pooch might also be right as rain after some physical therapy. Otherwise, severe cases of luxating patella in dogs are usually treated with surgery. No matter what treatment option you go for, most dogs recover and live long, normal, active lives.
If your dog is suffering grade 1 or 2 luxating patella and it is not causing huge problems, you and your vet might decide to pursue conservative, non-surgical treatment.
One treatment option is physical therapy. The aim here is to strengthen your dog’s quadricep muscles and the other soft tissues in their leg so that they can better support the knee joint and keep it stable. Your dog could visit a veterinary physical therapist, enjoy hydrotherapy, or you can do some work at home to help strengthen their quads. Getting your dog to repeatedly sit and stand a few times or climb stairs a few times a day will all help to build those muscles up.
However, physical therapy will not help a serious case of patella luxation in dogs and it will not fix a physical abnormality that is causing the problem, like a shallow trochlear groove. Physical therapy must be approached with the advice of your vet, and following professional guidance to make sure you don’t do too much exercise or attempt any activities that could make your dog’s condition worse.
Following surgery, your dog will have to wear a brace or bandages to support their knee. This will usually only be needed for a few days.
You can also buy braces to support your dog’s knee if they suffer from luxating patella, similar to how you might wear a brace on your wrist if you suffer from repetitive strain injury. These braces typically involve a soft sling around your dog’s knee which attaches to a harness along their body.
There is little evidence or study on the effect of these braces on dogs. They might help to support the knee and alleviate discomfort, however, they will not treat the underlying problem that is causing the condition.
If your dog’s patella luxation is caused by an abnormality in their anatomical structure, then your vet might suggest surgery to correct the knee joint. There are various different surgical approaches they might take, but the outcome is always to align the knee joint and strengthen it so it is less likely for the kneecap to pop out of place.
If your pup’s luxating patella is caused by a shallow trochlear groove, the surgeon will cut out a section of bone from the femur to create a deeper groove, with higher walls that are more likely to keep the kneecap in the correct position.
Another option is for the veterinary surgeon to stabilise the knee joint by adjusting the soft tissues around it. Depending on the direction of your dog’s luxation, they will tighten the tissues on one side of the leg to increase tension, and relax the tissues on the other side. This adjustment should help to reinforce and stabilise your pup’s knee so it’s more likely for their kneecap to stay in place.
If your dog’s patella luxation is caused by misalignment of their quadricep mechanism or patellar ligament, then your vet can adjust the placement of the ligament to straighten it all out. This will involve cutting and moving a little bit of your dog’s shin bone where the ligament is anchored, shifting it into a new position so that the quadriceps, kneecap, and patellar ligament can form a straight line.
The moved bone will be anchored in place with a few metal pins. This adjustment to their leg means that the quadricep and ligament mechanism can work like a pulley and bend and straighten your dog’s leg like it’s meant to. And now that it is a straight line, the kneecap will glide through the groove correctly rather than being pulled to either side and out of place.
As with any surgery, there is no 100% guarantee that it will make your dog completely better. However, the vast majority of dogs who have surgery return to completely normal limb function and can go back to living their best lives!
The outlook is typically very good for dogs following surgery for luxating patella. They can only have very limited exercise for about 1 to 2 months following their procedure. Their recovery will involve plenty of crate rest to limit their movement, and very short walkies just to go to the toilet and back. Your dog will not be allowed to run, jump, or play with other dogs at this time. It might feel like you’re being a killjoy, but it means your pooch can make a full recovery and is less likely to suffer from future injury.
Your dog might benefit from physical therapy or hydrotherapy to begin rebuilding their muscles after their operation and to gradually and gently increase the range of movement in the leg again. Your vet might give you some exercises to do at home with your dog to help increase their comfort, encourage normal leg movement, and strengthen their limb.
Most dogs who have surgery regain normal limb function. In some cases, surgery might not entirely fix the condition and a pooch might suffer some stiffness or very occasional dislocations. These can often be treated with medication and physical therapy to relieve any inflammation or pain in the knee and will further strengthen your pup’s leg to stabilise the joint and encourage normal function.
Regardless, luxating patella is not a condition that can be fatal for dogs and luxating patella itself won’t shorten their life. However, it will impact their movement and quality of life if left untreated and could lead to weight gain due to lower activity levels.
Obesity, in turn, can shorten your dog’s life and make them more susceptible to other health problems so it’s important for your pooch’s health and wellbeing that they stay active and problems like luxating patella are properly managed.
Written by: Dr Andrew Miller MRCVS
Andy graduated from Bristol University in 2010 and sees nutrition as a foundation for our pet's wellbeing and takes a common-sense approach. We are what we eat, and it shouldn't be any different for our pets.