Patellar luxation is also known as kneecap dislocation.
The result is usually intermittent lameness that may progress to constant lameness.
About 90% of the dogs will have a very good outcome following surgery.
What is it?
Patellar luxation is also known as kneecap dislocation.
The result is usually intermittent lameness that may progress to constant lameness.
This condition may result from an anatomical abnormality at the level of the hip joint which then results in malalignment of the thigh muscles which are attached to the kneecap. This pulls the knee cap out of the trochlear groove located at the bottom of the thigh bone.
If the kneecap is frequently pulled out of its groove, this may also result in twisting of the femur (thigh) and tibia (shin) bones. In addition, the groove may become very shallow, thus providing minimal support for the kneecap.
Anatomy
The knee is made of two bones called the femur (thigh bone) and the tibia (shin bone) - see illustration to the right.
The bottom of the femur bone has a depression in it called the trochlear groove, in which the patella is seated.
The quadricep muscles are attached to the top of the patella, which is then attached to the tibial crest by the patellar ligament. These structures must align the patella over the trochlear groove.
Play the animation to the right to see a demonstration of patellar luxation.
Clinical signs
Breeds commonly affected:
Yorkies, Poodles, Boston terriers, and many other small breeds are over represented.
Large breeds can also be affected, but are less common:
Labrador retrievers, Golden retrievers, and Akitas are in this group.
Age:
This condition frequently affects dogs under one year of age, but it is also seen in mature dogs.
Sex:
Males and females are equally affected,
Signs:
Symptoms include a skipping gait, unwillingness of the pet to jump on elevated surfaces, and intermittent or constant lameness.
Stiffness is seen when arthritis develops in the stifle joint.
Acute severe lameness may be noted if the cranial cruciate is concurrently torn (see information on the TPLO and lateral imbrication technique to correct this problem)
Diagnosis
The diagnosis of this condition is made based on physical examination findings. Although radiographs (x-rays) are not needed to diagnose the condition, they may be recommended to assess the degree of twisting of the bones and to rule out other concurrent conditions.
Blood work is performed prior to surgery to asses internal organ health.
Treatment
Surgery is indicated if your pet has a luxating patella AND has a gait abnormality or lameness
The surgical procedure may include a combination of the following:
Deepening the trochlear groove
Cutting the tibial crest off the tibia bone and realigning it so that the patella lines up with the trochlear groove; pins are used to reattach the tibial crest onto the tibia bone
Tightening the soft tissues along the side of the joint
Straightening the femur bone by cutting the bone; the cut bone is held together with a plate and screws - this procedure is uncommonly needed in small breed dogs and is sometimes needed in large breed dogs
Potential complications
Infection at the surgical site is uncommon as sterile technique is implemented.
Anesthetic reactions are uncommon and rarely result in mortality under the care of our trained specialists.
Break down of the repair is possible, especially if your pet's activity is not restricted or he/she takes a fall.
Prognosis
About 90% of the dogs will have an excellent good outcome following surgery.
A very severe degree of patellar luxation may not have as good of a prognosis.
MVS Surgery Team
Click on a name below to read a biography of a team member:
