Patella luxation is a term used when the kneecap dislocates from where it usually sits in the knee and is a common orthopaedic condition.

It is most commonly seen in smaller breeds of dog, though can occasionally occur in larger breeds and in cats. The patella can luxate medially, where it moves to the inner side of the leg, or occasionally it can luxate laterally, where by it moves over towards the outer surface of the leg. Both types of luxation can cause lameness, though the severity of the lameness will depend on the severity and frequency of the dislocation.

What are the clinical signs?

Clinical signs of patellar luxation can be variable depending on the severity of the luxation. The signs can include intermittent hopping lameness of the effected hind limb, non-weight bearing lameness of the hind limb or persistent continuous lameness.

How is it diagnosed?

Most cases can be diagnosed by examining the pet either conscious or sedated and radiographs (x-rays). Patellar luxations are classified in grades by the severity of the luxation as shown below.

Grade 1 – The patella can be pushed out of the groove, however immediately returns to a normal position, this isn’t generally associated with any clinical signs.

Grade 2 – The patella remains within the groove for the majority of the time but spontaneously moves out of the groove during limb movement.

Grade 3 – The patella is luxated out of the groove most of the time but can be replaced back into the groove.

Grade 4 – The patella is permanently luxated out of the groove and cannot be replaced.

Treatment Options

Conservative treatment may be possible in mild cases, or in older animals that are coping acceptably with the condition, and will mainly involve weight management, physiotherapy/hydrotherapy regime and lifestyle alterations. However, in the majority of the cases surgical treatment is indicated in order to correct the dislocation and allow the patient to live a full and active life.

Surgical intervention will usually involve a variety of techniques aimed at encouraging the patella to remain in the groove where it usually sits. This may include deepening of the groove if it is too shallow, or realignment of the muscles and ligaments attached to the patella so that their pull no longer causes it to dislocate.

These radiographs demonstrate a dog with grade 4 patella luxation and corrective surgery. Before Surgery  and After Surgery 

Before
After

Post operative Care

Post surgery the dog must be strictly rested for the first week and go out only for toileting purposes and for a very short period of time. Once the dog has been checked he/she may be able to start very short, gentle lead walks and this should continue for the next 7-8 weeks.

Trotting, running, jumping and playing with other dogs must be avoided, as well as slippery surfaces and stairs. Sometimes cage or room confinement is recommended when unsupervised for the full recovery period.

If the dog bothers with the wound, we recommend keeping a buster collar until the wound is healed (normally around 10-14 days after surgery).

We advise taking follow up radiographs at 8-9 weeks post operatively, to assess bone healing; this can be done either with your local vet or ourselves. Once bone healing has been confirmed, lead walking can be gradually increased over a period of 4 weeks when the dog can return to normal unrestricted exercise.

If you have any concerns, please do not hesitate to give us or your vet a call.

What are the complications?

After surgery there is a low chance of complications. These include swelling, infection, reluxation of the patella, luxation of the patella in the other direction, breakage of the bones, implant loosening.