Knee joint and related structures

Home |Gross Anatomy | Topic Index | Chapter 9

Movements:
  • Flexion.
  • Extension.
  • Medial rotation of the flexed knee.
  • Lateral rotation of the flexed knee.

Muscles producing the movements:

Flexion:
  • Harmstrings

Others assisting:

  • sartorius,
  • Gracilis
  • Popliteus and also by the
  • Gastrocnemius
  • Plantaris when the foot is on the ground.
Extension:
  • Quadriceps femoris
  • Tensor fascia latae
Medial rotation of the flexed leg:
  • Popliteus,
  • Semitendinosus,
  • Semimembranosus
  • Sartorius and
  • Gracilis.
Lateral rotation of the flexed knee:
Biceps femoris
"Locking” and “Unlocking” mechanisms of the knee

Locking:

  • Additional 30° of knee extension caused by medial rotation of femur on the tibia.
  • Caused by longer articulating surface of the medial femoral condyle

Unlocking:

  • Initial 30° of knee flexion
  • Caused by lateral rotation of femoral condyle on the tibia.
  • Done by popliteus muscle