What to do when a dog goes 'weak in the knees' - Dr. Marty Becker

What to do when a dog goes ‘weak in the knees’

Thursday, Sep 14th, 2017 | By Dr. Marty Becker

You probably know my dog QT Pi Becker, a Jack Russell/Chihuahua mix shelter rescue and distemper survivor. He’s basically a canine amphetamine, always wired up and moving. But what you may not know is that when he’s moving, it’s not a normal gait. It’s more of a bunny hop, because he has what’s called luxating patellas, or knee caps that don’t stay in position.

This is almost always a condition present from birth, and it’s common in small breed dogs like Pomeranians, Chihuahuas, and Toy Poodles, although it can happen because of an injury.

The anatomy of a dog’s leg is very similar to ours. The patella is embedded in the tendon that connects the large, powerful muscles in the front of the thigh to the tibia (lower leg bone). Normally it moves easily up-and-down in what’s called the femoral or patellar groove. It is very important to normal, pain-free movement. When the groove is shallow, the patella can dislocate inside or outside of the groove, making it difficult for the dog to flex or extend the leg normally. In fact, it can lock the leg straight out in what can look like a dog doing a salute with a back leg.

Does this condition need fixing? It all depends on the severity on the individual dog. Patellar luxation is graded I-IV, with Grade I being a kneecap that occasionally pops out, Grade II a kneecap that pops out of position easily but returns to its normal position. Grade III is a kneecap that is normally out of position but can be pushed back into normal position (that’s what QT Pi has).

Grade IV is a kneecap permanently out of position that can’t be pushed back into position. Grades I and II typically aren’t surgically treated, whereas Grades III and IV need surgery to prevent lameness and deformation of the back leg bones.

Surgery involves deepening the groove at the minimum, and may involve correcting angles of the bones that are forcing the patella out of the groove.

So the next time you see your dog doing a bunny hop, don’t say, “How cute!” Call the vet!