This is where the dog’s kneecap (patella) is dislocated from its groove on the front of the thigh bone (femur).

The kneecap slips inward over the inner ridge causing the dog to skip or sometimes yelp in pain.

When the leg straightens it will often slip back to its original place and the dog starts walking normally again, but in some cases, the kneecap is permanently dislocated.

The problem normally starts in the first two to three years of life and is most common in the small breeds like terriers, Chihuahuas, pugs and cavalier King Charles spaniels.

It is rarely seen in the larger breeds, and cats are occasionally affected.

Patella luxation can be very disabling in some dogs, whereas other dogs with the condition will hardly limp at all.

It is usually caused by a genetic malformation of the femur and tibia bones where they become misaligned.

It can occasionally be caused by trauma.

Affected dogs should not be bred from to prevent passing the problem on to the next generation.

Diagnosis of the condition is usually by careful palpation of the knee from your vet.

Sometimes x-rays are required to judge the severity of the condition so a treatment plan can be constructed.

Unfortunately, medications will not help a great deal, so surgery is usually the best option.

There are two surgical procedures available to treat patella luxation and depending on the severity of the condition, some dogs will either need one, or both procedures performed to keep the kneecap in the right position.

One of the surgeries involves realigning the top of the shin bone (tibia) which will make the patella track more to the outside and the other procedure involves making the groove at the front of the thigh bone deeper (also making the ridges higher).

After surgery, the dog will need a period of confinement and some may need physiotherapy, but most dogs will be able to run again on their new knee in about six to eight weeks.

So if you see your dog skipping on one or both legs, a visit to your vet is the wise thing to do.