During resisted hip flexion in the sitting position, the thigh shows lateral rotation and abduction when resistance is applied. Which muscle is the most likely substitute for hip flexion under these circumstances?

During resisted hip flexion in the sitting position, the thigh shows lateral rotation and abduction when resistance is applied. Which muscle is the most likely substitute for hip flexion under these circumstances?

• A. Tensor fascia latae
• B. Sartorius
• C. Adductor longus
• D. Semimembranosus

Answer: (B)

When the thigh shows lateral rotation and abduction during resisted hip flexion in a seated position, it signals a muscle that can flex the hip while also producing external rotation and abduction. The sartorius fits this pattern best because it crosses the hip obliquely from the ASIS to the pes anserinus and acts as a hip flexor with abduction and external rotation, especially when the hip is flexed. In this setup, the sartorius can substitute for pure hip flexion, producing the observed rotational pattern. The other muscles don’t match this combination as well: the tensor fascia latae can help with flexion and abduction but tends toward internal rotation effects with hip flexion; adductor longus mainly adducts the thigh; and semimembranosus is a hamstring that extends the hip and tends to rotate the thigh internally rather than externally or abduct.

When the thigh shows lateral rotation and abduction during resisted hip flexion in a seated position, it signals a muscle that can flex the hip while also producing external rotation and abduction. The sartorius fits this pattern best because it crosses the hip obliquely from the ASIS to the pes anserinus and acts as a hip flexor with abduction and external rotation, especially when the hip is flexed. In this setup, the sartorius can substitute for pure hip flexion, producing the observed rotational pattern.

The other muscles don’t match this combination as well: the tensor fascia latae can help with flexion and abduction but tends toward internal rotation effects with hip flexion; adductor longus mainly adducts the thigh; and semimembranosus is a hamstring that extends the hip and tends to rotate the thigh internally rather than externally or abduct.