Patella Luxation & Testing
Patella Luxation testing & scoring schemes in dogs;
Patella luxation in dogs is a condition where the patella or "knee-cap" can move from its normal central position at the front of the knee or "stifle joint" to one side or the other. This condition is more common in the smaller breeds, however it may occur in large breeds and also cats.
In most dog breeds the most frequent direction of abnormal movement or "subluxation" is towards the midline of the dog- "medial patella luxation". In some cases the subluxation can be away from the midline of the dog and is called "lateral patella luxation". The causes of this condition can be congenital, genetic and/or traumatic.
Patella Luxation testing & scoring schemes in dogs are organised by many responsible breed associations or societies in breeds which have an increased frequency of patella luxation.
The dog breeder or owners bring their dogs which they plan to breed from for an examination by a veterinary surgeon who is familiar with the Putnam Patella Luxation Grading System. The examination is normally performed during an orthopaedic examination without sedation. Radiographs are not required but may be arranged if requested.
In the UK & Ireland there is no official Kennel Club testing scheme for Patella Luxation as there are for Hip & elbow dysplasia and eye screening, however, some breed Clubs hold a database of those dogs which have been checked for patella luxation using the Putnam (1968) testing and scoring method.
What do the different scores mean in the Putnam Patellar luxation Grading system for dogs?
The Putnam grading system grades dogs from Grade 0- no luxation present- normal, to increasing severity from Grade 1-4.
The following description is used by some breed societies as guidance although slight variations in the wording and description exists between breed societies. Most breed societies provide their own forms for the vet to complete. We have provided links to some breed societies operating these schemes and patella subluxation assessment forms.
Grade 0: Normal
Grade 1: the patella can be manually luxated with the stifle in full extension, but when pressure is released without manipulation of the limb the patella regains its original position in the trochlea. Spontaneous luxation of the patella during normal joint motion rarely occurs. Typically stifle and hock in a straight line with no deviation of the hock.
Grade 2: the patella can be completely luxated, but manipulation of the hind limb (flexion of the stifle) causes the patella to regain its original position in the trochlear. On physical examination, the patella luxates easily, especially when the foot is rotated.
Grade 3: the patella is found (at least once) spontaneously luxated with the animal in a standing position or it is permanently luxated but can be repositioned manually or by manipulating the limb. Very shallow or flattened trochlear.
Grade 4: the patella is permanently luxated and cannot be repositioned. May scarcely be able to walk or may move in a crouched position with both limbs partially flexed, and/or they may carry the affected limb. Trochlea is shallow, absent or even convex.
Excessive force should not be used when manipulating the patella.
Where can I obtain the Patella luxation testing forms for my vet to complete?
SPCGB have a form available: Please email firstname.lastname@example.org with the Dogs;
KC registered Name
Registered Owners Name Address
A form will then be sent out for you to take with you to your vet or you can attend the SPCGB Championship Show where these tests are subsidised by the club and are free to members or £25 for non members. Your Shar Pei must be at least 12 months old for this test to be performed.
Dogs scored above 1/1 should not be used for breeding as its widely agreed that most cases of Patella Luxation are hereditary.
The causes of Patella Luxation are not completely understood. One known cause is trauma, such as an accident or injury. Although still fairly common, trauma-caused Patella Luxation cases are a small minority of the total number. Most cases are a result of genetics. The exact genes responsible are not known, and most researchers now believe that Patellar Luxation is a polygenic condition, meaning that several different and possibly unrelated, genes are responsible. Many researchers believe that a malformed femur, patella, tibia, or groove is responsible for Patella Luxation in many cases, although it does not appear that this is a universal consensus. Other veterinarians have suggested that malformation of tendons and ligaments may also play a key role. Although it is widely agreed that Patella Luxation is hereditary in nature, there is no agreement on exactly how it is inherited.