Introduction
The dislocation of the patella is a common orthopedic pathology, particularly in small-breed dogs. The ball joint (or patella) is a bone located in the tendon of the quadriceps muscle, essential to the proper functioning of the knee joint. When the patella moves abnormally out of its normal position in the femoral trochlea, we speak of dislocation. This condition can be medial (inward dislocation) or lateral (outward dislocation). Small breeds such as the Yorkshire Terrier, Chihuahua and Poodle are particularly prone to this condition. This article looks at the mechanisms of patella luxation, its diagnosis, treatment and prospects for recovery.
Aetiology and predisposed breeds
The dislocation of the patella is mainly caused by congenital or developmental abnormalities that affect the alignment of the extensor apparatus of the knee. Factors that may contribute to this condition include:
- Abnormal bone shape Malformation of the femur, tibia or tibial crest.
- Shallow or absent femoral trochlea or absent.
- Hip anomalies Certain hip deformities can increase the risk of dislocation.
Certain breeds of dog are predisposed to patella luxation, including :
- Yorkshire Terrier
- Chihuahua
- Miniature poodle
- Cocker Spaniel
- Boston Terrier
- Bichon Frise
- Bulldog
- Labrador Retriever
- Golden Retriever
Patellar dislocation can also occur in large breeds, although this is less common.
Symptoms of Patella Luxation
The symptoms of patella dislocation vary according to the severity of the dislocation (classified into 4 grades), and can range from simple discomfort to total inability to use the affected limb. Here are the most common signs:
- Intermittent lameness The dog may limp, skip a few steps, then regain a normal gait after shaking or stretching its leg.
- Cowboy gait Hindquarters may appear to bow inward.
- Decreased activity The dog may be less active or avoid games requiring rapid movement.
- Muscular atrophy Loss of muscle mass in the thigh due to lack of use of the limb.
- Knee pain The dog may show signs of pain when the knee is manipulated.
- Clunking sensation Dislocation of the patella may cause a noise or sliding sensation when manipulating the knee.
If left untreated, the condition can evolve into permanent lameness and lead to degeneration such as osteoarthritis.
Diagnosis of patella dislocation
Visit diagnosis of patella dislocation is based on clinical examination. Palpation of the knee allows us to assess the stability of the patella and determine the severity of the dislocation. Dislocations are classified into 4 grades:
- Grade 1 The patella can be dislocated manually, but returns spontaneously to its original position.
- Grade 2 Patella occasionally dislocates, but can be replaced manually or spontaneously.
- Grade 3 The patella is permanently dislocated, but can be replaced by manipulation.
- Grade 4 The patella is permanently dislocated and cannot be replaced manually.
From X-rays can be taken to assess bone structure, measure the degree of osteoarthritis and plan surgery if necessary.
Treatment Options for Patella Luxation
The treatment of patella dislocation depends on the severity of symptoms and the grade of dislocation. The main treatment options are as follows:
Surgical treatment
Surgery is recommended for dislocations of grade 2 or higher, especially when symptoms are present. Surgical techniques include:
- Transposition of the tibial crest This technique consists in moving the bony prominence where the patellar tendon attaches, thereby realigning the patella correctly.
- Medial desmotomy and lateral imbrication Medial desmotomy involves loosening the tissues on the side where the patella luxates, while lateral imbrication tightens the tissues on the other side to hold the patella in place.
- Trochleoplasty This technique deepens the femoral trochlea, providing better anchorage for the patella.
- Corrective osteotomies In the case of severe bone deformities, surgical correction of the femoral or tibial axis may be necessary.
Treatment Conservative
For grade 1In the absence of symptoms, regular monitoring is often sufficient. Conservative management includes :
- Weight control Optimum weight reduces pressure on joints.
- Physiotherapy Physiotherapy can help strengthen the muscles around the knee and improve joint stability.
- Chondroprotectors Glucosamine and chondroitin supplements help maintain joint health and prevent osteoarthritis.
Prognosis and post-operative management
The prognosis after surgery is generally excellent, with the majority of dogs returning to a normal life. However, proper post-operative management is essential:
- Strict rest for 6 to 8 weeks after surgery to allow healing.
- Rehabilitation and physiotherapy to restore mobility and prevent joint stiffness.
- Weight control to limit pressure on the joint.
Conclusion
The dislocation of the patella is a common ailment in dogs, particularly small breeds. A early diagnosis and treatmentSurgical and conservative treatments can significantly improve patients’ quality of life. General veterinarians should be alert to signs of intermittent lameness and abnormal gait to detect this condition.
