Knee Muscles

knee musclesKnee muscles are comprised of different muscle groups all performing different functions which maintain knee integrity and motion.  The knee joint is a hinge joint that is subjected to enormous stress during the normal activities of daily living.  Understanding knee muscles and how they correlate with daily function is essential for anyone looking to maintain optimal knee performance and reduce the risk of injury.  A routine of knee strengthening exercises should be added to your fitness program.

Knee anatomy

The knee muscles are connected to ligaments, cartilage and bone.  The distal femur, the proximal tibia, and the patella form the knee.  The knee is composed of two joints, the tibio-femoral and the patello-femoral joint.  Rotation around the hinge joint occurs at the tibio-femoral joint along with gliding and rolling.  The knee has extensive ligamentous support.  The primary stabilizer of the knee is the ACL (anterior cruciate ligament). The cruciate ligaments of the knee act to restrict rotation and anterior/posterior glide of the tibia beneath the femur.  Knee ligaments are commonly injured in sports, intense exercise, dance, extreme sports and other physical activities involving cutting or twisting.

Knee muscles and functions

Knee Muscles

  • Rectus femoris –  Knee extension and hip flexion
  • Vastus lateralis – Knee extension
  • Vastus medialis – Knee extension and patella stabilization
  • Vastus intermedius –  Mirrors the function of the vastus medialis
  • Semimembranosus – Extension of the hip joint, flexion of the knee and medial rotation of the knee
  • Semitendonosus – Duplicate mirror function of semimembranosus
  • Bicep femoris – Hip extension, knee flexion, slight lateral rotation

Below the knee muscles

  •  Gastrocnemius –Planter flexion and flexion of the leg at the knee joint
  •  Soleus – Forms the calf muscle with the gastrocnemius.  They mirror each other
  • Peroneals -Peronæi longus, brevis, and tibialis posterior are responsible for planterflexion in the ankle.  The Tibialis anterior and Peronæus tertius, are responsible for dorsiflexion

In addition the peronæus llngus everts the sole of the foot. The Peronæi  adhere the leg upon the foot.

 Common knee injuries

  • Petello-femoral syndrome (PFS)
  • ACL tears or ruptures
  • Meniscus tears
  • Degenerative joint disease
  • Patella tendon rupture
  • Tibia plateau fracture
  • TKR or total knee replacement

Knee Muscles are very important to keep strong and flexible.  If proper knee strengthening exercises are not completed on a regular basis injuries such as a knee meniscus tear or ligament tear may result.  Keep up the good work.


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