The love we have for our pets may have us skipping around in glee, but if you notice your dog occasionally skipping or limping, he or she may have a luxating patella (or floating kneecap). In a speedy 3 minute overview, The Meowing Vetย summarizes the signs of patellar luxation, which dog and cat breeds are most commonly affected, potential consequences of this orthopedic condition, and its treatments.
Learn more below…
A luxating patella (also called โpatellar luxationโ, โfloating kneecapโ, or โtrick kneeโ) is an orthopedic condition in which the patella (or kneecap) pops out of place. A medial patellar luxation (MPL) means the kneecap moves to the inner aspect of the limb while the less common lateral patellar luxation involves deviation of the kneecap towards the outer aspect of the leg (see diagram below). Both dogs and cats can be affected, yet this condition most typically affects toy breed dogs. Of cats, Abyssinians and Persians may be predisposed. The cause of patellar luxation is not fully understood, yet it tends to be a congenital or developmental abnormality (meaning the pet is born with it or it occurs during early growth) of the trochlear groove where the kneecap should normally sit or the muscles and ligaments that hold it in place when a back leg is extended. The condition is often bilateral, meaning both knees are often affected.
Luxating Patella Illustration from Dog Health (doghealth.com)
Signs of a luxating patella include:
- hopping or โskippingโ a step
- limping
- sitting with the affected hind limb rotated outwards
- sometimes knee pain
You may observe your pet stretching its leg backwards or sitting to โpopโ the kneecap back in place. A luxating patella can lead to cranial cruciate ligament (CCL or ACL) injury in some cases.
Your veterinarian will be able to easily diagnose this orthopedic problem upon examination and/or radiograph (X-ray, as depicted below).
Radiograph depicting medial patellar luxation from the American College of Veterinary Surgeons (ACVS) (acvs.org)
During orthopedic examination, your vet will ascertain the severity of your dog’s luxation, designating it as one of the following grades:
| Grade 1
(mild) |
Patella can be luxated medially when the stifle is in full extension |
| Grade 2 | Patella can luxate medially spontaneously |
| Grade 3 | Patella is permanently luxated but can be reduced manually |
| Grade 4
(severe) |
Severe disease with a nonreducible, permanently displaced patella |
Depending on severity, knee surgery with a surgical specialist may be necessary to ensure that the kneecap stays in place to prevent further knee injuries from occurring, such as tear of the cranial cruciate ligament (CCL) or worsening osteoarthritis. Surgical practices may include a combination of procedures, including trochleoplasty, tibial tuberosity transposition (TTT), and lateral imbrication & medial release. A stifle arthrotomy may also be performed to check other tissues within the knee joint.
- Tibial tuberosity transposition (TTT): laterally transposes the tibial crest (bony prominence of the tibia onto which the patellar tendon attaches below the knee) to prevent medial luxation of the patella by realigning the quadriceps, patella, and patellar tendon
- Left trochlear groove block recession or trochleoplasty: deepens the trochlear groove to better accommodate the patella
- Lateral imbrication & medial release: loosen & tighten the surrounding tissues to help maintain stability of the patella
- Stifle arthrotomy: to confirm no tear of the cranial cruciate ligament (CCL) or medial meniscus
Click here for additional surgical information.
Fortunately, many dogs and cats with a mild form of patellar luxation do quite well. However, if you observe signs of pain or mobility impairment in your pet, consult with your local veterinarian, who can also refer you to a boarded veterinary orthopedic surgeon.
– Maranda Elswick, DVM
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This article originally appeared as a post on The Meowing Vet’s Instagram profile, @themeowingvet (October 11, 2017).
