What is a Luxating Patella or Dislocated Knee
Patella is another word for the knee cap. The term luxating means ‘out of place.’ Therefore, a luxating patella in dogs occurs when the knee cap dislocates from its normal anatomic position. A luxating patella is also called a “knee trick.”
Where is the Patella Located
The almond-shaped patella rests in a groove of the end of the thigh bone (the femur). When the patella is luxating, the only way to get it back in its normal position is through the quadriceps muscles in the hind legs lengthening and relaxing.
For this reason, you may have seen dogs holding up and stretching their hind legs for minutes at a time as if they are stretching out a cramp of sorts. Accordingly, the dog may have been experiencing a patellar luxation.
What Does the Patella Bone Do
The patella serves to assist in knee extension. It rests in the tendon quadriceps muscle and attaches to the tibia. The tibia is the bone below the femur.
The quadriceps muscle contracts nearly every time a dog moves. As the muscle group contacts, it pulls on the tendon as well as the knee cap. Therefore, patella luxation occurs if the knee cap is pulled out its normal groove during knee extension.
What Causes Patellar Luxation
A luxating patella may have a variety of causes.
For instance, patellar luxation can be congenital, a genetic malformation, or a result of trauma.
Breeds with a Predisposition for Luxating Patella
Knee cap dislocation is of the most common knee joint conditions found in dogs. It is seen primarily in toy and miniature dog breeds.
Namely, here is a list of the small breeds of dogs that have a predisposition for luxating patella.
- Miniature and Toy Poodles
- Jack Russell Terriers
- Yorkshire Terriers
- Cavalier King Charles Spaniels
- Boston Terriers
Important to realize, large dog breeds are not entirely without worry of having a luxating patella.
Larger breeds have less of a genetic predisposition for patella luxation. Typically, they have deep, sturdy grooves for the patella to naturally sit in.
However, larger breeds are more prone to having problems with their hips. Joint issues above or below the knee can cause a sort of ripple effect of problems. Therefore, if a dog has joint issues their ankles or hips, it will likely cause issues in the knees as well.
Larger breeds that are apt to patellar luxation are:
- Labrador Retrievers
- Golden Retrievers
- St. Bernards
Small breed dogs have a greater predisposition for patella luxation due to a congenitally shallow trochlear groove.
Additionally, some small breed dogs, especially those that are bowlegged, may have an even higher probability of developing a luxating patella. This is because the attachment point of the patellar ligament is not at the midline of the tibia.
This brings us to how exactly the knee can luxate.
Patellas can luxate in two ways- towards the dog´s body (medially) or away (laterally).
Luxating Patellas Medially
One way that the knee can luxate is medially (towards the body). Breeds with a congenitally shallow trochlear groove, as well as dogs that are bowlegged with luxating patellas, generally always have medial patellar luxation.
This means that that point of attachment of the patellar ligament is located too far medially, or in other words, close to the middle of the dog’s body or the inside of the leg.
As a result, when the quadriceps muscles contract, the patella gets pulled up the side of the leg causing an abnormal movement known as medial patella luxation.
As time goes on and the abnormal movement continues to occur, the inner side in the trochlear groove of the femur wears down. For this reason, the trochlear groove wears down more and more, allowing the patella to have more freedom to move around and dislocate.
Pet owners may not realize that their dog is having joint issues because dogs usually don’t have any signs of pain or discomfort when the knee cap is out of place. This makes medial patellar luxation difficult to diagnose in its early stages, unless the dog owner knows exactly what to look for.
Luxating Patellas Laterally
Lateral patellar luxation can occur in both small and large dogs. When lateral patellar luxation exists bilaterally, dogs can have a genu valgus-type
, crouched posture.
In humans, we refer to this as ‘knock-knee.’ In fact, in humans, lateral patellar luxation is the most common form of luxation.
However, in dogs, lateral patellar luxation is discussed significantly less than medial patella luxation.
Generally speaking, lateral patellar luxation is most commonly seen in older, small breed dogs. However, it also occurs in young, large breed dogs.
When patellar luxation results from trauma, it can occur medially or laterally.
After any trauma to the legs, especially the knees, pet owners should take their dog to a veterinarian. A veterinarian exam is needed confirm that the cranial cruciate ligament (CCL) has not been ruptured.
A veterinarian will perform a radiograph of the stifles. The results will show if osteoarthritis is present, as well as any sign of cranial cruciate ligament damage.
If the cranial cruciate ligament is intact, usually a procedure will fix issues for the patella.
If the cranial cruciate ligament has been ruptured, a surgical technique called fibular head transposition (FHT) may be necessary to reconstruct the cruciate-deficient stifle.
With this said, there are certainly circumstances in which surgery isn’t necessary at all.
More Information on the Cranial Cruciate Ligament
Studies show that 15-20% of dogs with luxating patella will rupture the cranial cruciate ligament.
There are two main reasons for the rupture:
1. The biomechanics of the knee are altered from the luxating patella. This change causes additional stress on the cranial cruciate ligament.
2. When the luxating patella has experienced arthritic changes, the inflammation of the joint will cause ligaments, particularly cruciate ligaments, to begin deteriorating.
Genetic Patellar Luxation – More Than Just a Knee Issue
Specific breed disposition supports the idea that patellar luxation is a congenital abnormality of the entire extensor mechanism. Therefore, patellar luxation is not just a knee condition, but a result of multiple skeletal malformations.
Patellar luxation also affects:
- Malformation of the femur
- Irregular structure of the hip joint, such as hip dysplasia
- Abnormality of the tibia
- Deviation in the tibial crest
Symptoms of a Dislocated Patella
Specific symptoms of a dislocated patella vary based on the severity of the dislocation, as well as how long the condition has been happening and the underlying cause.
When the luxating patella is a genetic malformation, it is generally diagnosed quite early on. In this case, clinical signs of patellar luxation in dogs develop approximately four months after birth.
The most common symptoms of patellar luxation are:
- An occasional skip while walking or running
- Prolonged abnormal hindleg movement
- Sudden loss of support on the leg experiencing patellar luxation
- Abnormal sitting posture
- Lameness of the hindleg
Again, dogs rarely feel any discomfort or pain when the knee cap is out of place. Therefore, pet owners won’t be able to use signs such as whimpering as means to detect an issue.
Also, these symptoms happen intermittently, which also makes the problem difficult to recognize at first.
Degrees of Patellar Luxation
Medically, there are four varying degrees of patellar luxation.
1. Grade I:
A dog experiencing Grade I patellar luxation will not be in any pain. Additionally, when the knee cap pops out of place, it is able to be massaged back into its natural position. Your veterinarian can show you how to do this properly.
Also, since dogs primarily hold the majority of the weight on their front legs, if the luxation is caught early on, surgery is rarely necessary so long as the condition doesn’t progress.
2. Grade II:
A dog experiencing Grade II patellar luxation may encounter a few more issues with the affected knee. Comparatively to Grade I, the dog will rarely be in any amount of pain. However, they have a significant chance of developing arthritis in which case, pain in the knee will exist.
Also, while the knee can be massaged back into its natural position, it will often pop back out of place shortly after. Some dogs who have Grade II patellar luxation will need to have surgery to fix their condition.
3. Grade III
In Grade III patellar luxation, dogs are usually arthritic and in a substantial amount of pain.
The patella sits outside of its natural groove more than it is in it. While the patella can be manually placed back, it only stays temporarily.
4. Grade IV
Dogs with the most severe grade, Grade IV, of patellar luxation are experiencing the worst case scenario of knee joint issues. The dog’s natural groove where the knee cap is supposed to sit no longer exists. The patella cannot be put back into its natural position.
In Grade IV patellar luxation, the dog will always need surgery.
Diagnosing Patellar Luxation
A number of methods are used to properly diagnose a luxated patella. It may surprise you just how intricate diagnosing a dislocated knee cap can be.
Your veterinarian will most likely order top view (craniocaudal) and side view (mediolateral) X-rays of several parts of the body.
X-rays of the stifle joint (joint between the tibia and femur), hip, and hock can expose irregular movement and twisting of the thigh bone.
Additionally, in order to detect a curved, flattened, or shallow groove of the thigh bone, your veterinarian may request skyline X-rays.
Your veterinarian may also take a small fluid sample from the knee joint. By examining the lubricating fluid in the joint (synovial fluid), your vet will be able to determine any changes in the mononuclear cells.
A physical examination of the knee is also a requirement.
Luxating Patella Surgery
Every situation is different when it comes to surgically treating patellar luxation.
Some dogs live a full, healthy life with a luxating patella without it ever causing arthritis. Since the luxating patella doesn’t lead to pain, surgery is never required. This is more common in smaller dogs. As previously mentioned, larger dogs usually have additional joint issues in their ankles or hips.
In dogs with patellar luxation at Grade III or IV, luxating patella surgery is required more often than not. This is due to the arthritic pain involved. Otherwise, many dogs will have reduced leg function and joint damage that will negatively impact their day to day life.
How to Repair Patellar Luxation
Surgical correction to repair a patellar luxation is usually a three-step procedure.
1. The patellar ligament is attached to the proper point on the tibia. In many cases of patellar luxation, the point of attachment of the patellar ligament is located too far medially, or too close to the middle of the dog’s body.
2. The groove in the femur that the patella sits in is deepened. The deepening of the groove prevents the patella from easily moving out of place.
Large dogs have a deep femur groove that generally keeps the patella in place. In most cases, this step of the repair is geared towards small dog breeds.
3. When patellar luxation occurs, the joint capsule stretches. The third part of the surgery tightens the capsule which prevents the knee from dislocating from its normal position in the future.
Surprisingly, with proper care, the recovery from patellar luxation surgery can be quick and relatively simple.
Patellar Luxation Surgery Outcome
If your dog needs patellar luxation surgery, the prognosis is usually always very positive. With proper recovery, your dog should regain full usage of the leg.
It should be noted, if your dog’s luxating patella had significantly progressed causing arthritis in the knee joint, intermittent pain might still occur. In this case, your veterinarian may suggest anti-inflammatory medications.
Pet owners can also add natural anti-inflammatory supplements like turmeric for dogs to their dog’s diet to ensure they are feeling their best.
Patella Luxation Surgery Alternatives
Non-surgical methods will never change the anatomy of the dog. However, there are a number of things that dog owners can do in order to treat patella luxation without surgery.
Before we get into the non-surgical options, we want to mention an important fact.
Dog owners should recognize if by choosing a non-surgical method, they are merely postponing an inevitable surgery. If your dog has Grade III or IV patellar luxation, surgery will be required the vast majority of the time. Opting for a non-surgical option is only delaying something that is unavoidable and will decrease the probability of a full recovery.
There are many non-surgical methods for dog owners to consider.
- Diet – It is critical that your dog maintains a healthy weight and doesn’t become obese. Dog owners should make sure their dog has a healthy diet in order to sustain an appropriate weight.
- Exercise – Pet owners should walk their dog in short intervals every day. Walking your dog not only aids in maintaining a proper weight, but it also keeps the muscles in the legs healthy.
- Nutrition – If possible, switching your dog to a raw diet can provide incredible nutritional benefits. A raw diet can lead to improvements in cartilage conditions and help all the joints become healthier and stronger.
- Supplements – Glucosamine and chondroitin supplements can improve joint health.
- Acupuncture – Pet owners may want to look into a veterinarian who specializes in acupuncture of the knee. In some cases, acupuncture has shown to ease symptoms of patellar luxation.
Easing Symptoms of a Luxating Patella
Additionally, while pet owners cannot change their fur baby’s DNA, they can support their body’s immune system with essential nutrients and a healthy lifestyle.
- Vitamins B1 and B6 – necessary for collagen synthesis
- Mixed tocopherols (such as Vitamin E) – antioxidant properties, help ease inflammation from osteoporosis, and stabilize cell membranes
- Absorbic acids (Vitamin C) – antioxidant properties and aids in collagen synthesis
- Glycosaminoglycan – anti-inflammatory properties and necessary for collagen formation
- Chondroitin – anti-inflammatory properties and stimulates glycosaminoglycans
- Omega-3 fatty acids – anti-inflammatory properties and prevent cartilage degradation
- Methylsulfonylmethane (MSM) – necessary for collagen synthesis, aids in pain management, and reduces muscle spasms
- Bioflavonoids – antioxidant and anti-inflammatory properties
- Manganese – necessary for the synthesis of glycosaminoglycans and collagen
- Sulfur – required for collagen production
- Copper – aids in collagen synthesis
- Zinc – helps with collagen synthesis
- Magnesium – necessary for collagen synthesis
- Selenium with fish oil – antioxidant properties and reduces inflammation in joints
- Calcium – necessary for proper enzyme function
Let’s Get Physical
Exercise can be a paramount for easing symptoms of patellar luxation as well as for the prevention of symptoms from developing.
A dog with weak quadriceps muscles is at an increased risk for patellar luxation. Therefore, keeping your dog active is key!
Here are a few fun exercises to strengthen the quadriceps muscles, improve knee stability, and reduce the risk of patellar luxation:
- Walking up and down stairs (preferably carpeted)
- Zig-zag walking up and down a hill
- Sitting and standing several times in a row
- Army crawl (this is a skill that will require teaching – we recommend using treats and make sure the dog’s backside stays down to strengthen the quadriceps muscles)
- Leg weights can increase resistance and strengthen the muscles
- Swimming is a great exercise for building muscle and water buoyancy makes it safe on joints
- Water exercises also increase resistance that helps with joint support
#Goals for Treating a Dog with Patellar Luxation
- Support strong and functional connective tissue
- Supply the essential nutrients for collagen synthesis
- Control inflammation with natural anti-inflammatory supplements
- Supplement their diets with antioxidants
- Manage any pain or discomfort
- Prevent osteoarthritis from developing
Additional Info on Patellar Luxation
Knee conditions are often a sign of hip issues as well. Knee problems, as well as hip problems, are genetic and often pass onto the puppies. For this reason, pet owners should not breed their dog if it has patellar luxation.
Luxating patella is one of the most common orthopedic conditions found in dogs. Veterinarians diagnose approximately 7% of all puppies with patellar luxation.
While it does exist, luxating patellas in cats is very rare so your little floof is probably safe!
Final Thoughts on Patellar Luxation
Any time there’s an issue with (wo)man’s best friend, things can get pretty scary. Dogs aren’t able to tell us what is wrong with them, making it more or less a guessing game for pet owners.
Therefore, knowing what to look for is key in early detection. Avoiding surgery is possible if patellar luxation doesn’t reach an arthritic stage.
Furthermore, while patellar luxation sounds extreme, you may have a say in the severity. With proper nutrition, supplementation, and rehabilitation, pet owners may be able to avoid surgery altogether.
Lastly, we know you want what’s best for your pup. By staying aware and acting accordingly when necessary you can ensure that your dog is living the best life possible.
Words to Know:
Luxate means dislocate. (Other forms: luxating, luxated, luxation)
The patella is the kneecap. (Another form: patellar)
The femur is the thigh bone. The femur extends from the pelvis to the knee.
The inner bone between the knee and the ankle.
Define Stifle Joint
The stifle joint connects three bones: the femur, patella, and tibia. The stifle is located in the hind limbs of dogs. It is equivalent to the human knee.
Regarding patella luxation, medial means towards the body.
Regarding patella luxation, laterally means away from the body.