010-111 Question #189: Real Exam Question with Answer & Explanation

The correct answer is B. Hamstrings, Gracilis, and Sartorius. Knee flexion is performed by muscles that cross the posterior aspect of the knee joint. The hamstrings, gracilis, and sartorius all attach distal to the knee and produce flexion.

Question

Which muscles are used to flex the knee joint?

Options

AHamstrings, Gastrocnemius, and Soleus
BHamstrings, Gracilis, and Sartorius
CRectus femoris, Vastus Lateralis, and Vastus Medialis
DBiceps Femoris, Vastus Lateralis, and Sartorius

Explanation

Knee flexion is performed by muscles that cross the posterior aspect of the knee joint. The hamstrings, gracilis, and sartorius all attach distal to the knee and produce flexion.

Common mistakes.

A. The soleus crosses only the ankle joint, not the knee, so it cannot contribute to knee flexion despite the gastrocnemius being a valid knee flexor.
C. The rectus femoris, vastus lateralis, and vastus medialis are all quadriceps muscles that produce knee extension, not flexion.
D. The vastus lateralis is a quadriceps muscle responsible for knee extension, not flexion, making this combination anatomically incorrect for knee flexion.

Concept tested. Muscles responsible for knee joint flexion

Reference. https://www.acefitness.org/education-and-resources/professional/exam-prep-blog/knee-joint-muscles/

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