What is a patella and normal mechanism of the knee (stifle)
The knee is made up of three bony parts: the femur (thigh bone), the tibia (shin bone) and the patella (kneecap). There are various other soft tissue structures in the knee but the most important is the patella tendon. It is a fibrous connective tissue structure that runs from top to bottom of the knee on the forward facing side. The patella is interwoven into this structure and sits in a small groove under the patellar ligament. The patella and the patellar ligament together serve to facilitate smooth movement between the femur and tibia during flexion/extension of the knee.
What happens when the patella luxates?
Luxation is a medical term for displacement/dislocation of a bone from a joint. When the patella luxates it falls out of the groove discussed above, essentially the patella falls out of place. This can happen in one of two directions: medial (to the inside of the knee) or lateral (to the outside of the knee).
Is it out of place ALL the time?
Medial luxating patellas range in severity corresponds to the amount of time the patella spends out of its groove.
Grade 1: The patella can be moved out of place manually but falls back into place spontaneously, oftentimes called patella laxity.
Grade 2: The patella will fall out of place spontaneously but will also spontaneously fall back into the groove.
Grade 3: The patella is out of place all the time, but can be manually moved back into the groove
Grade 4: The patella is always out of place but cannot be replaced into the groove.
What does it look like in our pets?
Due to the range in grades, signs and symptoms often go along with the grades, as the grade becomes more severe the symptoms from the previous grade can also be seen.
Grade 1: Not wanting to jump, exercise intolerance – sometimes no symptoms at all
Grade 2: intermittent lameness, skipping gait
Grade 3: abnormal gait
Grade 4: Bow legged appearance, obvious gait abnormalities, signs of pain/discomfort, stiffness
What do we do about it?
Treatment for medial luxating patella is entirely dependent on the grade/severity. In most low grade cases there are no immediate interventions required. Higher grade cases sometimes require surgery. As dogs age the abnormal motion of the joint and joint capsule (the definition of joint disease) over time can increase the risk for arthritis. See other newsletters about arthritis!
BUT WAIT WHAT DOES REHAB HAVE TO DO WITH MEDIAL LUXATING PATELLA?
The MOST important things about the low grade laxity or luxations is maintaining strength and mobility as well as learning to recognize worsening symptoms. Your rehabilitation provider can curate a home exercise plan over the course of a few visits for you to keep your animal strong at home. As previously mentioned low grade laxities can be hard to spot and may lead to early arthritis, rehabilitation can help prevent/slow this!
Also while rehabilitation providers are not doing the surgical corrections they are imperative for the post operative phase should a pet require surgery.
Please reach out if you have questions or think your dog might need their patella’s evaluated.
