Knee Articulations

Flexion

Bending the joint resulting in a decrease of angle; moving the lower leg toward the back of the thigh.

• Hamstrings
• Gracilis
• Sartorius
• Popliteus
• Gastrocnemius

Extension

Straightening the joint resulting in an increase of angle; moving the lower leg away from the back of the thigh.

• Quadriceps femoris

Medial Rotation (Internal Rotation)

Rotary movement around the longitudinal axis of the bone toward the center of the body; with the knee bent, turning the lower leg inward.

• Popliteus
• Semimembranosus
• Semitendinosus
• Sartorius
• Gracilis

Lateral Rotation (External Rotation)

Rotary movement around the longitudinal axis of the bone away from the center of the body; with the knee bent, turning the lower leg outward.

• Biceps femoris