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Dislocation of the patella

The patella is a small rounded bone that slides in a groove in the front of the femur, like a pulley. It transmits force from the thigh muscle to the leg. We speak of dislocation when the kneecap comes out of its groove, most often towards...

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Definition Signs Causes Diagnosis Treatment Prevention Complications When to see a vet Prognosis FAQ Sources Affected species

What is it?

The patella is a small rounded bone that slides in a groove in the front of the femur, like a pulley. It transmits force from the thigh muscle to the leg.

We speak of dislocation when the kneecap comes out of its groove, most often towards the inside of the limb. The knee locks briefly, then the kneecap returns to its place on its own.

It is one of the most common orthopedic anomalies in dogs, particularly in small breeds. It is most often linked to the conformation of the skeleton and present from a young age.

Commonly observed signs

These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.

Related signs — each one links to its page:

Lameness Pain Stiffness Refusing to jump or climb Difficulty standing up

The dog runs, then lets out a short cry, raises one hind leg for a few strides and leaves normally: this is the most classic presentation.

Intermittent lameness, which appears and disappears for no apparent reason.

Small jump on three legs, followed by a stretch of the limb which puts the kneecap back in place.

In marked forms: crouching gait, knees permanently bent, limbs arched.

Refusal to jump up, get on the couch or in the car.

Stiffness and pain upon waking in adult dogs, when osteoarthritis has set in.

In severe forms in puppies, the limb may remain turned and the dog hardly uses it anymore.

When to consult without delay

This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.

Causes and risk factors

In the vast majority of cases, the cause is a conformation anomaly present during growth: groove of the femur too shallow, deviation of the pelvic bone or tibia, insertion of the tendon offset on the tibia. The assembly pulls the ball joint out of its rail.

Much more rarely, a dislocation appears in an adult dog following trauma to a previously normal knee.

A hereditary component is recognized: affected parents frequently transmit the conformation in question.

Small breeds and miniature breeds, in which the anomaly is particularly common.

Large breeds also affected, often with outward dislocation and more marked bone deformities.

Family history: puppies from affected parents are more often affected.

Excess weight, which increases the stress on an already misaligned knee.

Slippery floors and repeated jumps from furniture, which promote blocking episodes.

Diagnosis and care

Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.

The diagnosis is based primarily on examining the knee: the veterinarian moves the kneecap out and then in by hand, in different positions of the limb, and classifies the dislocation into grades according to its ease of movement and its ability to return to place on its own.

This classification directly guides the treatment decision.

X-rays of the pelvis, femurs and tibias clarify bone deformations and allow us to check the condition of the hips.

The veterinarian also looks for associated damage to the cruciate ligament, common in dogs who have been lame for a long time.

A CT scan may be offered before complex surgery in a very deformed dog.

Treatment

A slight dislocation, discovered by chance in a dog that does not limp, often does not require any surgery: we monitor it, we maintain a healthy weight and good musculature.

When the dog limps regularly, suffers, or when the dislocation is marked, surgery is suggested. It generally combines several actions: digging the groove of the femur, moving the point of attachment of the tendon to the tibia, tightening or relaxing the tissues around the joint.

In growing puppies with a severe form, early intervention prevents the bones from becoming further deformed.

After the operation, supervised rest and rehabilitation determine the result: short leash outings, thigh strengthening exercises, gradual recovery.

Pain treatment is based on medications prescribed by the veterinarian. Never give human anti-inflammatory drugs to your dog: ibuprofen, aspirin and paracetamol can cause digestive ulcers, hemorrhages and serious kidney or liver damage, sometimes fatal.

Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.

Prevention

Do not breed an affected dog: this is the only truly effective lever on a breed scale.

Have puppies' knees examined by the veterinarian during vaccination visits: dislocation is detected very early on palpation.

Keep the dog slim throughout its life.

Avoid repeated jumping from the sofa or bed, lay non-slip mats on smooth floors.

Maintain the muscles of the hindquarters through regular walks.

Possible complications

Osteoarthritis of the knee, which develops due to abnormal friction and becomes painful with age.

Wear of the cartilage and the femoral groove.

Rupture of the cruciate ligament of the same knee, favored by chronic instability.

Progressive deformation of the femur and tibia in untreated young dogs.

After surgery: recurrence of the dislocation, displacement of the material or infection, possible but uncommon.

When to see a veterinarian

Your dog suddenly lifts one hind leg for a few strides and then starts again normally.

He screams while running or jumping.

He has been limping on and off for several weeks.

He walks with his knees bent, in a squatting position.

A puppy has a turned or unused hind leg.

Lameness suddenly worsens in a dog already known for an unstable kneecap: damage to the cruciate ligament must be sought.

Prognosis

Light forms allow a completely normal life, provided you monitor your weight and check your knee regularly.

After surgery, most dogs find a functional and pain-free limb; the result is all the better if the intervention took place before the onset of significant osteoarthritis.

Severe forms with marked bone deformation require more extensive surgery and sometimes leave residual discomfort.

Frequently asked questions

My dog lifts one hind leg for a few seconds then leaves: is it serious?

This is the most typical sign of a kneecap that becomes dislocated and then comes back on its own. This is not an emergency, but it warrants a consultation: the veterinarian will assess the grade and tell you whether to simply monitor or consider surgery.

Is it always necessary to operate?

No. A dog that is not limping or in pain can be monitored without surgery. Surgery is considered when the lameness is frequent, painful, or when the dislocation is significant in a young dog still growing.

Is it hereditary?

A hereditary predisposition is recognized: the conformation which causes the kneecap to protrude is transmitted. An affected dog should not be bred, even if the condition is mild.

Can I put the ball joint back in place myself?

No. Do not handle your dog's knee: you risk causing him pain and aggravating the lesions. It returns on its own in the vast majority of cases; if the knee remains stuck, call the veterinarian.