dvm2 (6)The patella is the kneecap. The patella normally fits into a groove in the thighbone or femur. The patella slides up and down in this groove as the leg bends and straightens. Patellar luxation in dogs means that the kneecap has slipped out of the groove. There are several reasons why this injury happens, including malformation of the groove. Luxation may happen only occasionally, or may happen continuously. The kneecap may pop back into the groove on its own. The pet will be lame when the patella is out of place.

As a result of patellar luxation, dogs often develop other degenerative joint changes, such as osteoarthritis if left untreated. If a pet has a mild case of this condition one may not notice the actual luxation, but the dog may eventually develop pain due to osteoarthritis.

Patella luxation in dogs is one of the most common stifle joint abnormalities in dogs. Medial luxations occur in 75% of cases while bilateral involvement occurs in 50% of cases. This condition is uncommon in cats, but may be more common than suspected because most affected cats are not lame.

A dog that is affected with patella luxation will not walk on the leg, but instead will commonly hold it up. Some pets will exhibit occasional skipping or intermittent hind limb lameness but commonly progresses in young or mature dogs.

Patella luxation in dogs is sometimes thought to be genetic and is most common in toy and miniature breeds.

Patella luxation may be mild to severe and is classified in four grades. Grade I being the most mild and Grade IV is the most severe.

  • A Grade 1 luxating patella describes a kneecap that pops out (or can be manually popped out of place), but pops right back in on its own.
  • Grade 2 describes a kneecap that pops out of place and doesn’t always pop back in automatically, sometimes requiring manual manipulation to re-seat it.
  • A Grade 3 condition is when the kneecap sits outside its groove most of the time, but can be manually positioned back in the groove, where it stays temporarily.
  • Grade 4 luxating patella describes a worst-case scenario, where the kneecap sits outside the groove all the time, and won’t stay seated in the groove when it is manually popped into place.

Surgery is usually recommended in moderate or severe cases to stabilize the patella. During a patella luxation repair the groove in which the kneecap moves back and forth is deepened and a pin is inserted in order to tighten the knee alignment. Post surgically the pet’s leg is bandaged and kept on strict rest for 4-8 weeks. Dr. Djordjevich is always an available resource regarding orthopedic cases and is positioned to offer courtesy consultations by appointment.

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