In a patient with complete L3 paraplegia beginning gait training, which muscle would NOT contribute to gait fluidity?

• A. Rectus femoris
• B. Semitendinosus
• C. Iliopsoas
• D. Adductor magnus

Answer: (B)

When a person has a complete L3 spinal level injury, muscles innervated above that level can still work to support gait, while those below are typically paralyzed. For fluid gait, you rely on hip flexion during swing and knee control during stance, which depends on the intact nerves to those muscle groups.

Semitendinosus is a hamstring muscle innervated by the sciatic nerve (primarily the tibial portion), with roots typically below L3. In complete L3 paraplegia, those lower roots are not functional, so the hamstrings lose their activity. That means knee flexion and the associated hip-extension contribution from this muscle would not participate in gait, reducing gait fluidity.

The other muscles have functional innervation at this level or include portions that remain active: iliopsoas provides hip flexion to help swing through; rectus femoris contributes to knee extension and also hip flexion; adductor magnus has an adductor portion (and can contribute to hip stabilization and adduction). These functions can still aid gait even with an L3 lesion.

So the muscle that would not contribute to gait fluidity is the semitendinosus.