Patellar Luxation in Dogs: Grades, Signs, and Surgery

A slipping kneecap is one of the orthopedic problems veterinarians diagnose most often in a dog's hind limb. It shows up most frequently in small breeds, though larger dogs are affected too. Some dogs only skip a step now and then; others struggle with real mobility loss, and the difference usually comes down to grade.

What Patellar Luxation Is

Patellar luxation happens when the kneecap leaves its normal track in the trochlear groove of the femur. The slipping can be occasional or constant, and it may involve one hind leg or both.

In a healthy knee the patella glides smoothly along that groove while a dog walks, runs, and jumps. When luxation is present the kneecap drifts off track, most often toward the inside of the leg, which is called medial luxation. It can also shift to the outside, and lateral luxation turns up more often in larger breeds. Medial luxation is the more common of the two overall. The condition may be present from birth or develop after an injury, and over time the repeated slipping can wear cartilage, cause discomfort, and set the stage for osteoarthritis.

Why It Happens and Which Dogs Are Affected

Most cases are developmental and become apparent while a puppy is growing, though trauma can dislocate a kneecap in a knee that was previously normal. The underlying anatomy is usually what drives it:

• Abnormal angulation of the femur or tibia
• A trochlear groove that is too shallow to hold the kneecap
• A tibial crest displaced toward the inside or outside of the leg
• Weak soft tissue support or an unbalanced pull from the quadriceps

When the bones and soft tissues of a growing puppy line up poorly, the kneecap tracks abnormally. Often nothing seems wrong until the dog starts skipping or moving differently. Pomeranians, Chihuahuas, Miniature Poodles, and Yorkshire Terriers are among the small breeds commonly affected, while Labrador Retrievers and German Shepherds are larger breeds that more often show lateral luxation.

Signs to Watch For

What you see at home depends on how severe the luxation is and how often the kneecap slips. Common signs include:

• Intermittent skipping or a bunny-hop step on one hind leg
• A sudden extension of the leg, after which the dog walks normally again
• A clicking or popping sound
• A bowlegged or knock-kneed stance
• Reluctance to jump or take the stairs
• Stiffness after resting or after exercise
• Lameness or discomfort that gradually worsens

Dogs with Grade I or II luxation may seem free of pain, showing only an occasional odd step. In the higher grades, dogs often become unwilling to put weight on the leg, and joint inflammation and arthritis can build up over time.

The Four Grades and When Surgery Is Considered

Veterinarians sort severity into four grades, which shapes both treatment and prognosis.

• Grade I: the kneecap can be pushed out of place by hand but slides back on its own; many dogs show no signs at all, or only very mild lameness.
• Grade II: the kneecap slips out now and then, particularly during activity, and returns either on its own or with help; a mild, recurring skip or lameness is typical.
• Grade III: the kneecap sits out of place all the time but can still be repositioned by hand; lameness is usually moderate or constant, and posture changes.
• Grade IV: the kneecap is permanently out of place and cannot be pushed back; limb deformity and serious mobility problems often go with it.

Diagnosis starts with a hands-on orthopedic exam, where your veterinarian feels how the kneecap tracks and checks for joint looseness, muscle tension, and muscle loss. Standard X-rays follow, showing the kneecap's position, the depth of the groove, and any bone deformity or existing arthritis. CT and MRI are rarely necessary, though they may be used in complicated or surgical cases.

Surgery is generally recommended for Grade III and Grade IV dogs, for Grade II dogs with ongoing lameness or loss of function, and when the changes are starting to strain the opposite leg or the hips. The goal is to realign the quadriceps mechanism, hold the kneecap in its groove, and prevent further joint damage. Techniques include deepening the femoral groove, transposing the tibial tuberosity to realign the patellar ligament in selected cases, and soft tissue work such as tightening the joint capsule or releasing tight tissue. Surgeons combine these based on each dog's anatomy and the direction the kneecap slips; not every dog needs every step.

Recovery and Long-Term Joint Health

Recovery varies with the procedure performed and how active your dog is. Most veterinarians build a rehabilitation plan around controlled movement, pain management, and physical therapy, tailored to the individual dog.

Once the knee has healed, a few habits protect it for the long run: keeping your dog at a healthy weight, feeding a joint-supportive diet with omega-3s and good-quality protein, discussing supplements such as glucosamine, chondroitin, or green-lipped mussel with your veterinarian, avoiding slippery floors and high-impact activity after surgery, and keeping regular follow-up appointments so healing and gait can be checked.

Left untreated, more severe cases can lead to chronic pain, worsening osteoarthritis, compensatory injury to the other leg or the hips, and in rare cases permanent deformity. Treating the problem early, before cartilage damage sets in, helps avoid those outcomes. With timely diagnosis and the right treatment, dogs with patellar luxation generally do well and go on to live comfortably. Your own veterinarian is the right person to weigh your dog's size, activity level, and joint health and to tell you which path fits.