The Knee Muscles

Muscles Around the Knee

  • Quadriceps Femoris (quads)—Large group of four muscles on the front of the thigh that helps to extend (straighten) the leg. All four muscles converge to form the quadriceps tendon, which attaches to the tibia, via the patella and patellar ligament (or tendon). Includes the:
    • Vastus lateralis—Exists on the lateral (outer) side of the anterior (front) thigh.
    • Vastus intermedius—Exist on the anterior and central part of the thigh. It lies underneath the rectus femoris (see below).
    • Vastus medialis—Exists on the medial (inner) side of the anterior (front) thigh.  Helps to stabilize the patella (knee cap).
    • Rectus femoris—On the anterior (front) thigh. It is also a weak flexor of the hip (bends the hip).
  • Sartorius – A slender and long muscle that comes from the anterior pelvis and attaches to the medial tibia to help form the pes anserinus (see below). Not a very strong muscle itself, it helps with multiple motions of the hip and knee.
  • Gracilis – Another slender and long muscle that comes from the pelvis and attaches to the medial tibia to help form the pes anserinus. Also a relatively weak muscle that helps with multiple motions of the hip and knee.
  • Hamstrings – Located on the posterior (back side) thigh. Bends the knee. Includes the following 3 muscles:
    • Semimembranosus – Attaches to the medial tibia
    • Semitendinosus – Attaches to the medial tibia. It is the 3rd muscle of three (in addition to gracilis and sartorious) that contributes to the pes anserinus.
    • Biceps femoris – Attaches to the head of the fibula
  • Gastrocnemius—The main bulk of your calf muscles. There are two heads, one along the posterior (backside) lateral (outer) leg and one along the medial (inside) leg. They attach to the heel bone (calcaneus) via the achilles tendon. This muscle plantarflexes the ankle (toes towards the ground) allowing you to stand on your tip toes. It also helps to bend the knee.
  • Pes Anserinus (the goose’s foot)- the tendinous attachment of the sartorious, gracilis, and semitendinosus on the medial tibia. It is covered by the pes bursa which can sometimes become irritated leading to pes bursitis.

Images of Muscles Around the Knee

Muscles Around the Knee Front (anterior) View

Muscles of the knee
Muscles Around the Knee

Muscles Around the Knee Inside (medial) View

Muscles Around the Knee Medial View
Muscles Around the Knee Medial (Inside) View

Normal Knee Anatomy