Human Anatomy - Kotsan I. Ya. 2009

General overview of the muscles responsible for movements of individual body parts
Movements of the lower limb
Movements of the leg at the knee joint

When the thigh is fixed (with a proximal support), the Muscles surrounding the knee joint perform flexion, extension, pronation, and supination of the leg; when the leg is fixed (with a distal support), they move the thigh forward, backward, and perform its pronation and supination.

Leg flexion. The flexor Muscles of the Leg cross the frontal axis of the knee joint and are located posterior to it. These muscles include:

1) biceps femoris;

2) semitendinosus;

3) semimembranosus;

4) sartorius;

5) gracilis;

6) popliteus;

7) gastrocnemius;

8) plantaris.

Leg extension is made possible by the quadriceps femoris, which crosses the frontal axis of the knee joint anteriorly. The Muscle has four heads:

1) rectus femoris;

2) vastus lateralis;

3) vastus intermedius;

4) vastus medialis.

Pronation of the leg at the knee joint is possible only as the leg flexes, i.e., when the collateral ligaments are relaxed. The muscles performing this movement are located posterior and medial to the knee joint:

1) semitendinosus;

2) semimembranosus;

3) sartorius;

4) gracilis;

5) medial HEAD of the gastrocnemius;

6) popliteus.

Supination of the leg at the knee joint occurs (just like pronation) as the leg flexes. The supinators of the leg are muscles located lateral to the joint:

1) biceps femoris;

2) lateral head of the gastrocnemius.