Positioning:
                  Tilting of the X-ray to the side or forwards toards the camera will adversely affect the score to some degree. There may even be uneven scoring in terms of right v left side and extra 3 or 4 points depending on the degree of lift. The effect will be largely on the first three items. Tilting is unlikely to effect the last six items to any degree.
    Reader:
                  Readers can differ slightly in interpretation. The BVA use two readers from a panel of 9 or 10 selecting fairly randomly. All panellists are Diplomates of Veterinary Radiology (DVR) and thus highly eperienced. Nevertheless even they can differ slightly in their interpretation of plates. If a user feels that the score was wrong then appeals are dealt with by their cheif scrutineer (Dr G Clayton-Jones). In AVA and GSDCA  schemes one readeris used and in the NZVA scheme two readers.These schemes also have appeal systems.
    Anaesthetic:
                  Recent information suggests that anaesthetics can give rise to greater joint laxity than will sedatives. Thus a dog that is anaesthetized MAY  show a higher score for Norberg angle and Subluxation than the same dog would if merely sedated. Most schemes seek to anaesthetize dogs and thus all are being compared on valid terms. If however, a breeder is submitting animals that are sedated it could lead to slightly lower scores and thus apparently better results than rivals who are using anaesthetics. Thismust be borne in mind when considering score data.
    Sex:
                  In man, female children are at greater risk of HD than males. In the dog it looks as though a similar status exists. In most breeds with enough data females score some 3-4 points higher than do males. This has nor been observed in OFA data but is seen in British, Australian, and Scandinavian data for the majority of breeds.
    Age:
                  In OFA data a large age effect is claimed. With scoring the effect appears to be much less. For every month of life after 12 months hip score increased by from 0.07 to 0.17 points. This is quite small and suggests  minimals age effect in score data. However, good hips will show alomost no change while poor hips may show a larger effect. Breeders are urged to score as soon after 12 months but gaint breeds might be better at 18 months.
    Breed:
                  Breed effects are known, with some breeds at high risk others low. The belief is that this was associated with growth rate or 60 day-weight is now less tenable. Although larger-sized breeds generally tend to be more prone to HD than smaller sized ones this is not inevitable. Some of the sight hound types are less affected by HD than other similarly sized breed but even among large breeds there are quite marked differences and the occassional badly dysplastic sight hound is seen. We find the large Ptrenean Mountain dog better in terms than the equally large Newfoundland. Similarly some small breeds e.g. Tibetan Terrier may be more seriously affected than some large breeds Irish Wolfhound.
    Muscle:
                  Pelvic muscle mass was considered important but modern thinking suggests that pelvic muscle might be concerned in minimising clinincal signs. The pectineus muscle of the inner thigh is believed to be implicated HD and its resectioning might allievate pain. Growth rate may have a slight effect with more rapid growth adversely influencing hip status. Nutritional plane can be used to minimise HD but only severe restriction which might also adversely affect physical shape.
    Exercise:
                  This is unclear but excessive exercise in early puppyhood seems unwise. If one had bred for bad hips then a failure to exercise will not necessarily prevent HD occuring. In dysplastic dogs exercise is necessary to maintain muscularity which will be lost if the dog is not exercised. Such dysplastic dogs need exercise little and often,            preferably lead work on hard surfaces.
    Synovial fluid:
                  This is a lubricant in joints. Excess synovial fluid is implicated in HD particularly through hyaluronic acid, a component part of the fluid, where a reduced concentration is associated with greater HD.
    Hormones:
                  Hormones are thought to influence HD but evidence is unclear. However it is known that SOME bitches will show greater joint laxity during oestrus and thus score higher. It is recommended that for this reason bitches NOT be X-rayed for the scheme during oestrus.
    Vitamin C:
                  There is no evidence that Vitamin C is implicated in HD. Indeed use of large amounts of vitamin C to combat HD is contra-indicated and not recommended. Breeders are therefore urged not to use Vitamin C in a belief that HD will be avoided. It will not be!
    Type:
                  Contrary to popular belief in some circles there is no evidence that extreme angulation or the lack of it is related to HD. In the GSD some evidence exists to suggest that long backed animals with crouching hindquarters are associated with greater HD. Since long backs and crouching hindquarters are undesireable in any event there is no reason to seek these features. Features in other breeds are unexamined.
    Unilateral Hip Dysplasia:
                  In all breeds some 80% or more of dogs differ by four points or less between hips and thus HD largely a bilateral state. However, some dogs score unevenly. At times this is a positional feature but in some it is not.
                  Dogs can score unevenly because of trauma (injury) or due to transitional segments on the spine but a proportion of dogs are uneven and will breed this feature on.
    Breeding:
                  Breeders should select as good a hip as they can in both males and females, bearing in mind breed average. The lower the hip score the better the broad terms but they should look at the where points are scored and try not to use animals scoring over 3 in any one place and certainly not mate animals where both score high in the same features.
                  The individuals own score must suffice initially but a good hipped dog from a good pedigree (parents / grandparents) is a "better bet" than one with a less good pedigree. Dogs with good litter mates are also potentially    safer than dogs with poor litter mates and to this end the scoring of littermates, whether show dogs or pets, is desireable as an aid to breeding. However, once progeny data are available on sufficient progeny this is more useful than the data on the animal or its pedigree/litter mates etc.