Patellar luxation is a common condition in dogs. The patella (knee cap) should run in a groove at the end of the femur (thigh bone). In some dogs the patella can luxate (dislocate) to the inside (medial) or outside (lateral) of the leg. Most commonly we see dogs with a medial patellar luxation. More commonly we see patellar luxations in small breed dogs like Yorkshire Terriers, Chihuahuas, and Cavalier King Charles Spaniels, however we also recognise the problem in large breed dogs like Labradors and Staffordshire Bull Terriers.
Patellar Luxation
Patellar Luxation
How does it affect dogs?
Dogs with patellar luxations are often lame. Owners commonly describe a skipping lameness, were the dog is lame for several strides before returning to normal. Some dogs can have a patellar luxation that causes no clinical problem. Long-term, if the patella is luxating frequently, cartilage wear can occur on the back of the patella and on the end of the femur causing osteoarthritis. Patellar luxations are graded from 1-4 with grade 4 being the most severe. (Grade 1 means the patella can be luxated but returns to a normal position whereas grade 4 means the patella is permanently luxated). The problem is development, so progresses as dogs grow. With a medial patellar luxation a slight bowing of the leg causes the quadriceps muscles to line up more toward the inside of the leg. This pulls the patellar more toward the inside of the leg, which stops it running in the patellar groove. This means the groove does not develop to be deep enough and the patella continues to luxate. Patellar luxations can also occur following trauma, can be made worse with concurrent cranial cruciate ligament rupture, and can be associated with hip dysplasia.
How do we treat it?
If lameness is frequent surgical stabilisation of the patella is advised. Normally we deepen the patellar groove (sulcoplasty), realign the quadriceps mechanism (tibial tuberosity transposition) and tighten the soft tissues (imbrication). The tibial tuberosity is secured in its new position with pins and wire which hold it in place whilst it heals. Dogs require strict rest for around 6 weeks following surgery. This involves short lead walks for toileting, and no running, jumping or climbing stairs. In dogs that have severe deformities of their femur or tibia it may be necessary to straighten the bones to enable the patella to run in normally. This is called a corrective osteotomy.
How well do dogs recover?
Recovery from surgery to correct a patellar luxation is generally straightforward. Dogs would be expected to return to normal activity. In a small number of cases a recurrent luxation may occur and revision surgery may be required. This normally only affects dogs with the most severe grades of patellar luxation. In most dogs in the pins and wires remain in the leg once the bone has healed. In a small proportion of cases they may need to be removed if any discomfort is noted.
