The medial luxating patella, commonly called a “trick knee”, is an extremely common problem in toy breed dogs. An owner typically notices a little skip in the dog’s step, or sees the dog intermittently limp on one of the back legs, and then go back to normal gait.
In these cases, the kneecap (patella) has slipped out of the smooth groove in which it normally rides up and down. Hopefully, the patient will be able to slip the kneecap back where it belongs and be back to normal in only a few steps. For some dogs, getting a kneecap back where it belongs and normal extension of the rear leg may require surgery. Approximately 50% of affected dogs have both knees involved while the other 50% has only one knee involved.
Which Dogs Need Correction?
Medial patellar luxations are graded to assess severity.
- Grade 1:
- Grade 2:
- Grade 3:
- Grade 4:
The kneecap can be moved out of place manually but will fall back into its natural position once the manipulator lets go. Dogs with Grade 1 luxations do not require surgical repair.
Same thing except that the kneecap does not move back to its normal position when the manipulator lets go. These dogs are likely to progress to arthritis development and should be considered for surgery to prevent conformational damage. There is some controversy over whether grade 2 dogs should have surgery. Grade 2 dogs may benefit from surgery and most often the owner is called upon to judge how big of a problem the lameness is for the pet’s quality of life at home.
The patella is out of place all the time but can be manipulated back into its normal position manually (though it will not stay there). Dogs with Grade 3 or 4 disease definitely should have surgery.
The patella is not only out of place all the time but cannot even be manipulated back into place by hand. Such a dog has extreme difficulty extending his knees and walks with his knees bent virtually all the time. Dogs with Grade 3 or 4 disease definitely should have surgery.
It is not a good thing to have one’s kneecap out of place; the entire weight-bearing stress of the rear leg is altered which, in time, leads to changes in the hips, long bones, and ultimately arthritis. How severe the changes are depend on how severe the luxation is (i.e., the grade as described above) and how long that degree of luxation has been going on. The luxation is not considered to be painful initially but after enough time the rubbing of the kneecap against the joint can cause arthritis, which is painful. This surgery is a procedure that not all veterinarians are comfortable performing. Discuss with your veterinarian whether referral to a specialist would be best for you and your pet.
