168 Charter 5_Pelvis, Hip, and Thigh
Figurę 5-6. A, B, and C, Posterior aspect of ihe thigh. A, biceps femoris; B, scmitcndinosus; C, semimembranosus.
knee extension, whereas passive extension of the knee may cause iiwoluntary hip extension by the same mechanism. Medial Aspect
Thigh. The medial thigh is bordered by the vastus medi-alis and sartorius anteriorly and by the hamstrings pos-teriorly (Fig. 5-8). Bctwcen these margins are located the adductor magnus, the adductor longus and the gracilis muscles. The adductor magnus originates from the ischial tuberosity and inferior pubie ramus and inserts on the femur in two places: the linea aspera of the posterior femoral shaft and above the medial epicondyle in the area often referred to as the adductor tubercle. The adductor magnus is the bulkiest of the adductor muscles. The adductor longus arises from the anterior pubis near the pubie symphysis and inserts on the linea aspera. The adductor longus is the most distinctly visible of the adductors. Its proximal portion stands out in the medial groin when the leg is maximally abducted or placed in the figure-four position (Fig. 5-9). The gracilis originates on the medial pubis and inserts on the tibia, where, along with the overlying sartorius and adjacent semitendinosus tendons, it forms the pes anserinus.
Two aspects of alignment are usually associated with a hip examination: evaluation for leg length discrepancy (lower limb length discrepancy) and evaluation for rota-tional malalignment of the lower limbs. Both of these qualities may be affected by factors outside of the hip, the pelvis> and the thigh. For purposes of coherence and con-tinuity, these other factors are discussed herc.
Leg Length Discrepancy
Differences in the lengths of a patients lower limbs are usually described as leg length discrepancies, although lower limb length discrepancies would really be morę accurate because the overall lengths of the lower extrem-ities are what are being compared.
Pelvic Obliquity. Abnormalities of limb length usually result in obliquity of the pelvis; therefore, a check for pelvic obliquity is an excellent starting point to begin the alignment examination. In a normal patient, the two sides of the pelvis should be level with each other when the patient is standing. To check for pelvic obliquity, the patient is asked