Patellar Luxation (Slipping Kneecaps)

Overview

- The patella is the kneecap; luxation means slipping or dislocating

- Medial patellar luxation is slipping towards the inside; lateral is slipping towards the outside; more than 75% of dogs and cats with patellar luxation have the medial form

- Involvement of both kneecaps, called bilateral patellar luxation is seen in more than 50% of patients

Description of the Pet

- Recessive multiple genes and multifocal inheritance has been proposed

- Hereditary in Devon Rex cats

- Predominantly in dogs, uncommon in cats

- Most common in toy and miniature dogs, including poodles, Yorkshire terriers, Pomeranians, Peckingese, Chihuahuas, Boston Terriers

- Risk of females is 1.5 times greater

- Causes: congenital or trauma

Signs (Observed Changes)

- Depend on the severity of the luxation, the amount of degeneration of the joint due to the luxation, and the presence of any other knee problems; typically graded from 1 to 4, with 1 being the mildest form of the problem and 4 the most severe

- Persistent rear leg carriage in puppies

- Occasional, gradually worsening skipping or intermittent lameness in young dogs

- Sudden lameness

- Evidence of pain is variable

Treatment

- Medical management involves weight control, anti-inflammatory medication, and supplements that protect and enhance the quality of the joint tissues, including glucosamine/chondroitin and omega fatty acids; physical therapy and laser therapy are other valuable options

- Surgery is usually not needed but is available

- Do not breed affected pets; do not repeat breeding of parents that produced affected offspring

Prognosis

- With surgery, greater than 90% of pets are free of signs

- Degenerative joint disease (progressive and permanent deterioration of the cartilage and other joint tissues) invariably occurs, but for most small dogs the impact is minimal

modified from:  Blackwell's Five-Minute Veterinary Consult: Canine and Feline, Fifth Edition, Larry P. Tilley and Francis W.K. Smith, Jr. © 2011 John Wiley & Sons, Inc.