Name: Patellar Luxation
The knee joint has three major components; the thigh bone (femur), the lower part of the leg (tibia bone), and the kneecap A normal kneecap usually rests within a groove on top of the thigh bone. The medical term for this groove is trochlear groove.
The condition patellar luxation takes place when the knee flexes and the kneecap moves outside of the groove. The repeated recurrence of the kneecap dislocating, will cause the erosion of the cartilage, which will lead to arthritis.
Any dog can develop patellar luxation but it primarily affects small and miniature breeds with a predisposition for the condition, such as the Maltese, Jack Russell Terrier, Miniature Poodles, Yorkshire Terrier, Pomeranian, Pekingese, Chihuahua, Papillion and Boston Terrier. In the past 10 years there has been a rise in patellar luxation occurring in larger breeds, such as the Golden Retriever, Labrador Retriever, Chinese Shar Pei, Boxer, Great Pyrenees and Akita.
Most dislocated kneecaps are caused by a congenital (present from birth) defect, but they can also occur due to trauma. In half of all patellar luxation cases both kneecaps are affected. Female dogs have patellar luxation more often than males. In cases of congenital patellar luxation, clinical signs may appear between the ages of 4 to 6 months.
Types of Patellar Luxation in Dogs
There are 2 types of Patellar luxation:
- Medial luxation - Medial luxation occurs when the kneecap moves out of the groove and toward the opposite leg. A medial luxation prevents the dog from fully extending his leg. The kneecap will usually pop back into its normal position after a couple of steps
- Lateral luxation - Lateral luxation occurs when the kneecap slips and moves away frm the body. This type of knee dislocation is more common in large breed dogs, especially dogs with hip dysplasia.
Symptoms of Patellar Luxation in Dogs
Symptoms of patellar luxation will vary depending on to severity of the condition. Symptoms may include:
- Avoids placing weight on the leg
- Abnormal gait
- Holds leg up for a few steps
- Puppies with medial patellar luxation may appear “bow-legged”
- Dogs with lateral patellar luxation may have a knocked-knee stance
- Foot may twist to the side
- Swelling on or around the knee
Causes of Patellar Luxation in Dogs
Patellar luxation may be caused by:
- Trauma (e.g., hit by a car, kicked)
- Genetic - abnormalities/disorders, which may cause patellar luxation to occur include:
- Femoral groove is too shallow
- Malformation of the lower leg bone (tibia)
- Atrophy of the thigh muscles (quadriceps muscles)
- Loose patellar ligaments
- Hip dysplasia
Diagnoses of Patellar Luxation in Dogs
The veterinarian will want to know what symptoms you have observed and when did they start. The veterinarian may ask to see the dog walk, to evaluate the patient’s gait. During the physical exam the doctor will palpate (touch/feel) the dog’s limbs and kneecaps. If he feels an abnormality in the knee, he will recommend x-rays of the pelvis, knee and tibia. He may also recommend a CT or CAT scan, which can provide a three-dimensional image of the dog’s entire leg. The dog will need to be sedated for these procedures.
Treatment of Patellar Luxation in Dogs
Depending on the grade level of the patellar luxation, treatment may be medical management or a surgical procedure. The grade level of patellar luxation goes as following:
- Grade 1 - The kneecap moves out of the femoral groove occasionally, but returns to its normal position on its own.
- Grade 11 - The kneecap moves out of the femoral groove more frequently but can be returned into the groove by manipulation.
- Grade 111 - The kneecap dislocates most of the time but can be returned into the groove by manipulation. The groove is very shallow and flattened.
- Grade 1V -The kneecap dislocates but can’t be returned into the groove by manipulation. The patella is permanently luxated.
Grade 1 patellar luxation is usually treated with medical management instead of surgery. The veterinarian may recommend nonsteroidal anti-inflammatory drugs (NSAIDs), which helps to reduce inflammation and pain. Additionally, the patient may be started on physical or hydrotherapy therapy. If the patient is overweight, a lower caloric diet will be recommended. Losing weight will put less stress on the knee.
Dogs diagnosed with grade level 2-4 patellar luxation will require surgery to correct the disorder. The most common patellar luxation surgeries are:
- Trochleoplasty - The surgical procedure trochleoplasty is meant to correct a shallow groove by deepening the area. This procedure can only be done in young dogs, which have thicker cartilage to work with.
- Tibial Tuberosity Transposition - Tibial tuberosity transposition involves the realignment of the lower leg bone (tibia) and the knee cap.
- Lateral Imbrication and Medial Imbrication - Lateral imbrication and medial imbrication loosens or tightens ligaments on either side of the kneecap. This helps the kneecap to stay in place
Prognoses of Patellar Luxation in Dogs
If your dog underwent surgery you will be given specific post-operative instructions by the veterinarian surgical team. The patient will need to wear an Elizabethan collar until the sutures are removed. Sutures are usually removed 2 weeks after surgery. The dog will have activity restrictions for approximately 8 weeks. Physical therapy may be started 3-4 day after surgery. Most patients make a full recovery 30-60 days after surgery, depending on the particular surgical procedure done.
Patients with grade level 1 -111 patellar luxation usually have a good recovery prognosis.
Dogs with grade 4 patellar luxation may show less improvement depending on the severity of the kneecap abnormalities. Follow up visits will be necessary to monitor the patient’s progress and to remove the sutures.
Prevention of Patellar Luxation in Dogs
Due to the genetic implication, patients diagnosed with patellar luxation should not be used for breeding. There is no way to prevent congenital patellar luxation. Weight control can help the disorder not to rapidly progress.