Plain English summary
Patellar luxation (slipping kneecap) describes a condition where the kneecap (patella) can dislocate (slip) from its normal groove at the bottom of the thighbone (femur). This may be painless initially but can progress to arthritis later, causing pain and chronic lameness. Affected dogs are typically born normal but develop leg problems as they grow, which can allow the kneecap to slip abnormally in and out of its groove in the knee joint. This prevents the dog from bending its knee and can cause severe friction and rubbing of the surfaces of the joint, leading to arthritis. For some dogs, the kneecap remains permanently out of the groove giving permanent disability. Although patellar luxation is believed to be common in dogs in England and to be more common in certain dog breeds, particularly small breeds, precise information for the general population of dogs in England is lacking. The VetCompass Programme collects de-identified medical records from veterinary clinics in the UK to allow investigation of health conditions in dogs.
In this study of 210,824 dogs attending 119 veterinary clinics in England, patellar luxation affected 1.3 % of dogs overall. These dogs were managed in different ways; 39 % were treated with medication, 13 % had surgery and 4 % were referred for specialist veterinary management. The Pomeranian, Chihuahua and French Bulldog were particularly predisposed to patellar luxation. Dogs that were female, neutered (castrated or spayed) or below the average weight for their breed were at increased odds of diagnosis. Dogs that were covered by pet insurance were also more likely to be diagnosed. Most dogs were young when first diagnosed.
This is the largest study of its kind looking at patellar luxation in dogs attending veterinary general practices in England. It is clear that many dogs are affected and that there are breed-related genetic/inherited factors that predispose to patellar luxation. The welfare impact of patellar luxation on dogs in England should be taken into consideration in breeding programmes of commonly affected breeds.