Luxating Patella in Dogs: Causes, Symptoms, and Treatments

What is Luxating Patella in Dogs?

In dogs, a luxating patella (also known as patellar luxation) is an orthopaedic condition in which the kneecap (patella) becomes displaced from its normal position as the knee flexes. The patella sits at the base of the patellar ligament, which connects the large thigh muscles to the shinbone. Whenever the thigh muscles contract, they pull on the shinbone via the ligament, thereby extending (straightening) the knee.

A luxating patella is typically hereditary, where genetics influences the anatomy of a dog’s knee. The bones and muscles of the hind limbs may be misaligned, causing the patella to move toward the inside of the knee joint instead of moving normally. Moreover, the femoral groove where the kneecap sits may not develop properly and may become shallow, further increasing the risk of dislocation.

Traumatic injuries to the knee can also put your dog at risk of a luxating patella. For example, a vehicular accident may cause tearing of the soft tissue structures surrounding the kneecap, thereby increasing the risk of dislocation.

In most cases, a luxating patella occurs towards the inside of your pet’s knee, which is known as medial patellar luxation (MPL). There is also a risk that the dislocation occurs on the outside of the knee, known as lateral patellar luxation (LPL). MPL commonly affects smaller breeds, such as Pomeranians, Toy Poodles, and Terriers, whereas LPL may affect larger breeds. However, LPL cases are generally rarer than MPL cases.

Symptoms of Luxating Patella in Dogs

Consider taking your dog to a veterinarian if you notice any of the following signs:

• Skipping or hopping gait

• Sudden lifting of one leg

• Noticeable weakness in hind legs

• Reluctance to jump or climb stairs

• Crying or signs of pain

• Worsening lameness over time

Some of these symptoms may also arise in other orthopaedic conditions, so a thorough physical exam by a veterinarian will help determine the definitive cause.

Luxating Patella Grades & What Causes Each Stage

A luxating patella in dogs is classified into one of four grades, which depend on the condition’s severity. The higher the grade, the greater the risk that your dog will develop long-term complications.

Grade 1

Your dog’s kneecap slips out occasionally but will naturally return to its normal position. This typically occurs due to mild congenital bone misalignment, weak thigh muscles, or early genetic predisposition.

Grade 2

The kneecap slips in and out intermittently, sometimes requiring manipulation, but it can still return to its normal position. Some mild skipping lameness may be observed. Grade 2 cases may be due to a shallow femoral groove, or mild bony abnormalities.

Grade 3

At this grade, the kneecap is dislocated most of the time but can be manually repositioned. However, it is able to luxate much more easily than in earlier grades, leading to more frequent skipping lameness. Grade 3 is generally caused by progressive joint deformity, long-term, untreated Grade 1 or 2 cases, or obesity, which increases joint strain.

Grade 4

Your dog’s kneecap is permanently dislocated and cannot be manually repositioned. Grade 4 is the result of severe congenital deformity or long-term progression without proper treatment, which could cause persistent lameness and significant pain when your dog tries to move the affected limb.

How Is Luxating Patella Diagnosed?

Physical Examination

If you suspect that your dog may have a luxating patella, a physical examination performed by a professional veterinarian can confirm your dog’s condition. They will assess your dog’s legs and gait, including gently palpating the legs, to determine if your dog has a luxating patella. The vet can then provide a grade based on the severity of the condition and your dog’s history.

Limb X-Rays

X-ray scans may be performed to determine the extent of your dog’s luxating patella and assess for other changes or abnormalities in the knee joint based on the condition’s grade. The latter is essential for detecting and subsequently treating any bony deformities that may be present. As dogs with grade 4 patellar luxation often have severe underlying bony deformities, a CT scan may be required to fully assess the extent of the condition.

Non-surgical Treatment Options for Luxating Patella in Dogs

Non-surgical treatment is typically recommended for grade 1 cases of luxating patella. It aims to reduce inflammation and improve your dog’s long-term comfort, while also reducing the risk of future complications. However, non-surgical treatment methods serve as adjunct measures that help relieve pain, but do not halt the progression of a luxating patella.

Weight Management

If your dog is overweight or obese, the excess weight can significantly strain their joints, gradually causing damage and impacting their overall mobility. Weight management programmes aim to help your dog maintain a healthy weight, reducing this strain. These programmes include adjusting meal portions and promoting regular exercise to manage your dog’s weight.

Physiotherapy

Physiotherapy involves targeted exercises to slowly restore your dog’s leg mobility and range of motion. These activities also help reduce pain and discomfort while strengthening the knee joint and the surrounding muscles. Regular physiotherapy sessions are guided by a vet physiotherapist, who will conduct suitable activities to support your dog’s treatment while closely monitoring their condition.

Joint Supplements

The vet may prescribe joint supplements to preserve your dog’s joint health and delay future complications, such as osteoarthritis, that could arise in higher-grade cases.

Surgical Treatment Option for Luxating Patella in Dogs

The overarching goals of surgery for a luxating patella are to eliminate pain and lameness, realign the kneecap to restore knee flexibility and mobility, and preserve joint health against other conditions, including arthritis.

Surgery is typically recommended for grade 2 to 4 cases of luxating patella. While grade 2 and 3 surgeries are considered routine, grade 4 cases will require more complex surgical intervention. Routine patellar luxation stabilisation surgery involves tibial tuberosity transposition (TTT) and block recession trochleoplasty, in addition to soft tissue technique. Grade 4 cases often require correction of more severe bony abnormalities.

Surgery is also recommended for dogs who have had little success with non surgical management options, and the dog continues to suffer from patellar luxation. Over time, prolonged patellar luxation leads to development of arthritis and pain.

Tibial Tuberosity Transposition

This surgical procedure realigns the patellar ligament’s point of attachment so that it may facilitate normal knee movements. It involves cutting the bone where the ligament attaches and then repositioning it to prevent further patellar luxation. This bone is secured using pins and wire.

Trochleoplasty

A block recession trochleoplasty is performed to deepen the femoral groove to stabilise the patella and prevent it from luxating.

Soft tissue techniques

The joint capsule and surrounding fascia are imbricated to further stabilise the patella.

If other health complications make surgery unfeasible for your dog, a non-surgical treatment plan will be prepared to ensure their comfort. Should you suspect your dog may have a luxating patella, we encourage you to visit Westside Veterinary Emergency and Referral Hospital immediately to prevent further complications.