A dog’s patella, or knee-cap can luxate (slip out of place) there are varying degrees but, at its most severe it can be a painful condition for the dog.
A competent vet can manipulate the dog's legs to check for signs of a slipping patella and will assess whether the dog’s patella are normal. In cases where the patella is luxating the vet should be able to ‘grade’ the problem, eg from mild to severe.
Dogs should be checked for this condition on maturity, ie after 12 months of age, and again should any symptoms arise, eg if a dog regularly ‘hops’ on one of its rear legs.
In severe cases an operation to fix the joint may be required.