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374 20 Hip Region

recumbency and slow, deliberate force is placed by holding the stifle and pushing the femur
dorsally while the other hand stabilizes the sacrum. The hip is at neutral range of motion and
held in slight abduction to differentiate hip pain from SI pain. Pain is thought to be elicited by
stressing the dorsal SI ligaments. Movement testing is done in humans to evaluate amount and
quality of movement of the SI joint with voluntary flexion of the limb and trunk. While not vol-
untary motion, a dog’s hip can be flexed and extended and quality and amount of motion of the
iliac spine can be assessed for symmetry (Edge-Hughes 2007). Muscles used for stabilization of
the pelvis can be assessed for strength including the gluteals, latissimus dorsi, multifidus,
abdominals, and epaxials. Caution must be used in making such assessments, however, as these
can be weak with other orthopedic and neurologic disease such as HD, and lumbosacral or
thoracolumbar disease. Along with muscle strength, flexibility testing can be performed,
particularly of the hamstrings, piriformis, sartorius, iliopsoas, adductors, tensor fasciae, and
latissimus dorsi. The abdominal obliques may show asymmetry. Finally, evaluating for hyper-
and hypomobility of the SI joint via direct palpation while stressing the joint in a craniocaudal
direction and dorsal-ventral direction can be performed.
As the diagnosis of SI joint dysfunction is in its infancy, no definitive treatment currently exists.
Case reports of rehabilitation have been reported and a method of injecting the SI joint with ultra-
sound guidance was described in a cadaveric model (Jones et al. 2012), as this is commonly per-
formed in humans and horses for pain non-responsive to physical therapy. Accuracy of injecting
the SI synovial joint space was deemed fair to poor, although accuracy of injecting the synchondro-
sis and ventral and dorsal ligaments was deemed good. This modality needs further investigation
to evaluate its potential for widespread clinical use.

20.9.2 Septic Arthritis
Septic arthritis (Figure 20.16) of the hip joint has been described and is generally seen in dogs with
HIP REGION 20.9.3 Muscle Strains and Tears
preexisting OA (Benzioni et al. 2008). Please refer to Chapter 14 for further information.

Muscle strains represent a common reason for pain and orthopedic dysfunction in people. Because
these injuries are frequently self-limiting and diagnosis involves advanced imaging, only limited
information exists in veterinary medicine. However, one study of canines reported that the adductor,
pectineus, and iliopsoas may be prone to acute, stretch-induced injury (Nielsen and Pluhar 2005).
Acute gracilis muscle rupture, also termed “dropped back muscle,” has been described in the
racing greyhound (Eaton-Wells 1992). With such acute injury there is often significant soft tissue
swelling and bruising, unlike with gracilis contracture. Repair of the muscle tear generally allows
the dog to return to racing.

20.9.4 Hip Region Neoplasia

The most common neoplasia of the hip is proximal femoral osteosarcoma that may be difficult to
differentiate radiographically from OA in some cases. OA and osteosarcoma may also occur simul-
taneously, making establishing a diagnosis even more challenging. Well positioned radiographs
and additional views (e.g. frog leg) can help to detect subtle lucencies and pathologic fractures
(Figure 20.16), but advanced imaging (e.g. CT/MRI) may be necessary. Further details about
neoplastic conditions affecting the region are provided in Chapters 11 and 22.