## 1 Introduction  
Canine Hip Dysplasia (CHD) is a hereditary orthopedic disorder that predominantly affects large and rapidly growing dog breeds. It is characterized by abnormal development of the hip joint, resulting in laxity (looseness) of the joint, where the femoral head (the rounded top part of the thigh bone) does not fit securely within the acetabulum (hip socket), leading to instability [1]. Over time, this instability promotes abnormal joint wear, which often progresses to degenerative joint disease (DJD), commonly known as osteoarthritis, a condition where the joint becomes inflamed, painful, and stiff due to the breakdown of cartilage and the development of bone spurs. In milder cases, instability causes subluxation (partial dislocation of the femoral head from the acetabulum), while in more severe cases, it can progress to luxation (complete dislocation) [1]. The development of CHD is influenced by a complex interaction of genetic predisposition and environmental factors, such as diet and exercise. Radiographic imaging remains the cornerstone of CHD diagnosis, with the ventrodorsal hip-extended (VDHE) view serving as the standard imaging technique for evaluating hip joint conformation, in which the dog lies on its back with its hind legs stretched out to provide a clear view of the hip joints. This approach is vital for guiding clinical management and informing breeding practices to reduce CHD prevalence [1]. The screening process for CHD follows standardized radiographic scoring systems developed by major international organizations such as the Federation Cynologique Internationale (FCI), British Veterinary Association/Kennel Club (BVA/KC), and Orthopedic Foundation for Animals (OFA). The FCI classifies hips into five grades (A-E) and has historically relied on the Norberg Angle (NA) to assess joint subluxation and acetabular morphology. The BVA/KC system evaluates multiple morphological parameters, incorporating the NA, subluxation, and DJD criteria. In contrast, the OFA applies a categorical grading based on hip joint congruency without numerical scoring [1,2]. Building upon these methodologies, [PERSON] introduced a refined scoring system in 1993 to enhance CHD assessment objectivity while aligning with FCI standards. This system incorporated six radiographic parameters, prominently including the NA and the position of the femoral head center relative to the dorsal acetabular edge (FHC/DAE), alongside signs of DJD, to provide a holistic view of hip joint health [3,4]. The NA has traditionally been used as a key metric for CHD scoring according to FCI criteria, assessing the angular positioning of the femoral head relative to the acetabulum, thereby reflecting the extent of subluxation and acetabular depth [5]. An NA of \(\geq\)105\({}^{\circ}\) is typically viewed as indicative of sufficient hip joint integrity, implying a lower risk of developing DJD. However, studies have revealed limitations in using the NA alone to predict DJD susceptibility [6, 7, 8]. [PERSON] et al. demonstrated that an NA of \(\geq\)105\({}^{\circ}\) may fail to identify dogs at risk for DJD, as it can overlook joint laxity, a critical risk factor that becomes apparent only under stress or outside the standard VDHE radiographic view [6]. Consequently, some dogs with an NA \(\geq\) 105\({}^{\circ}\) may have underlying hip laxity, predisposing them to diagnostic inaccuracies and resulting in false negatives, allowing dysplastic genes to persist in breeding populations. Additionally, NA thresholds can vary by breed; for instance, Australian Shepherds and Borzois may exhibit NA values \(<\) 105\({}^{\circ}\) due to unique pelvic structures rather than true joint laxity [6,9,10]. Further complicating the issue, studies have demonstrated significant variability in inter-rater agreement for NA measurements. [PERSON] et al. observed an average inter-rater agreement rate of 72% when distinguishing between \"normal\" and \"dysplastic\" hips using the NA [11]. Similarly, [PERSON] et al.