What is a Luxating Patella in Dogs?
A luxating patella is a painful condition that occurs when the knee cap moves out of its normal position in dogs.
Patellar luxation is classified into several degrees or classes, ranging from mild luxation, in which the kneecap only luxates when directly stressed, to moderate luxation, in which the kneecap sticks out on a regular basis, to extreme luxation, in which the kneecap has dislocated the majority of the time. In affected dogs, one or both kneecaps may luxate to varying degrees. Some dogs can live their entire lives with this condition and not be affected long term, whereas for others, the inner side of the groove in the femur may wear down and cause permanent, painful issues. There are four grades:
- Grade l: Manual pressure causes the kneecap to dislocate from its natural position, but it quickly returns to its normal position when the pressure is relieved.
- Grade II: When subjected to manual pressure, the kneecap easily moves out of its normal position and remains displaced until manually corrected.
- Grade III: The kneecap is frequently disjointed but can be moved back into place with manual pressure. However, once the manual pressure is removed, the patella begins to luxate on its own.
Grade IV: The kneecap is dislocated from its normal position 100 percent of the time and cannot be manually repositioned.
What Causes a Luxating Patella in Dogs?
The patellar ligament connects the large thigh muscles to a point on the tibia and is located beneath the kneecap. The force generated by these muscles is transmitted to the shin bone via the patellar ligament. This causes the knee to straighten or extend. The patella slides up and down in its groove (trochlear groove) during this movement, which helps keep the patellar ligament in place.
A luxating patella in dogs can be caused by a traumatic injury, but it is more commonly caused by joint or limb structure abnormalities, such as the femur groove where the kneecap sits being too shallow, or the area where the kneecap attaches to the shinbone (tibia) being displaced.
Who’s At Risk of Developing a Luxating Patella?
Small and toy breed dogs such as Maltese and Chihuahuas, are likely to inherit a luxating patella. But in the end, all dogs can be at risk for a luxating patella.
What are the Symptoms of a Luxating Patella in Dogs?
The signs of a luxating patella may vary based on the grade of luxation. But the most common sign is a dog that suddenly skips while walking or run on three legs, and then the dog returns to normal.
Grade I is usually discovered by chance during a veterinarian’s examination and owners may not have noticed any physical signs of patellar luxation. With grade ll luxation, lameness can occur when the patella slips out of its normal position, and it can be uncomfortable and painful if the cartilage weakens as a result of repeated luxation. Grade lll causes gradual limb structure changes and/or cartilage damage from repeated luxation and causes increased pain, discomfort, and lameness in dogs. Grade lV symptoms include severe lameness, decreased mobility, and decreased limb function.
How is a Luxating Patella Diagnosed?
An orthopedic physical examination will be performed on the affected dog. Under sedation, the knee is palpated to assess ligament damage during this examination. X-rays of the pelvis, knee, and tibias will be done to assess the shape of the bones in the back leg and rule out hip dysplasia. A 3-D computed tomography (CT or CAT Scan) may also be done to provide an image of the entire back legs’ skeletal features In cases where the shape of the femur or tibia needs to be corrected. This advanced imaging technique usually assists the veterinary surgeon in planning the surgery.
What is the Treatment for a Luxating Patella?
The severity and grade of the luxating patella will determine the treatment options. Dogs with a grade l and ll luxating patella may be treated with pain and anti-inflammatory medications, exercise restrictions, weight management, and possibly physical therapy to rebuild strength. There are also braces that may assist in supporting your dog’s knee. Grade ll cases may also be treated with surgery due to the severe pain that is the result of cartilage damage. Both grade lll and grade lV are more often than not treated with surgery due to these grades severely affecting the dog’s quality of life.
The type of surgery varies based on if the correction is to either bony or soft tissue structures. But, the overall objective of luxating patella surgery is to realign the knee joint’s supporting structures so that the kneecap can move normally and stay in the femoral groove. Here are the most common strategies for luxating patella surgery:
- Reinforcing the soft tissue structures of the knee joint.
- Laterally shifting the joint that connects the kneecap to the shinbone.
- Deepening the groove on the femur where the kneecap sits.
- The tibial crest, which is the bony prominence below the knee where the patella tendon attaches, can be transposed to help realign the tendon, patella, and quadriceps.
For recovery, your dog may need to wear a soft bandage or brace for three to five days and have their exercise restricted for four to eight weeks after surgery to allow the site to heal properly. During this time of recovery, your dog’s walks should be limited to short on-leash trips to the bathroom, and they may need to be crated or confined to a small room to limit activity. Physical rehabilitation can help reduce muscle mass loss on the affected limb and may allow some dogs to return to normal function sooner.
How Much Does the Treatment for Luxating Patella Cost?
The rehabilitation route can cost anywhere from $40 to over $100 per session depending on the exact treatment type such as hydrotherapy versus laser therapy.
The cost of patella luxation surgery varies depending on where you live and who performs the procedure. General practitioners usually charge less than board-certified veterinary surgeons, who have more advanced training and experience with a variety of surgical techniques. The surgery can cost anywhere from $1,000 to $5,000.
What is the Prognosis for a Luxating Patella?
If surgery is performed, the prognosis is excellent and dogs should return to full use of their leg without pain. More than 90% of dog owners are pleased with their dog’s progress following surgery. In large dogs, the prognosis may be less favorable, especially when patellar luxation is combined with other abnormalities such as excessive long bone angulation or hip dysplasia. If your dog already has arthritis in the knee joint, he or she may experience intermittent pain in the leg and arthritis may progress. The possibility of recurrence of the luxated patella increases in higher grades but is not common.
When it comes to non-surgical treatments, one study revealed that long-term outcomes for dogs with grade l and ll patellar luxations who have been treated non-surgically were less favorable than those for dogs who were treated surgically. In this study, 33% of the limbs in that study were treated without surgery. 86% had excellent to good results, while 14% had fair or poor results.