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


  1. Max Fisher says

    Following a stroke, I find that when I take a step my right knee snaps into its straight position, causing inflamation and swelling in the joint. I suspect I have lost control of one or more muscles in my leg due to nerve damage, but can anyone tell me exactly which muscle/s?

  2. James Gardner says

    What would be wrong with my knee. Right above my knee it hurts. It hurts on all 4 sides of my knee. Top, right side of my knee, bottom center of my knee, and left sife of my knee.

  3. Hi i have a slight swelling just to the lower outside of the knee cap. Wondering what it might be, I did a strenuous yoga session today, and the area is throbbing,?

  4. David Cheang says

    I can’t bend my right knees.

  5. Frank Kwader says

    My knee is swollen and swelling on outside of lower leg. I laid my motorcycle down on it in gravel. When sitting I have extreme pain trying to lift my foot up. The pain runs along the shin bone halfway up my lower leg to base of knee. Caps ok , no pain, maybe a little click bottom of knee cap at base.
    Any ideas ? Thanks, Frank

  6. Cindy Schmidler says

    Hi, Dionnie! Thanks for reaching out to us with your question. Was the pain a result of physical injury or trauma? Your primary-care doctor should be the first specialist you visit to consult regarding your concern. If they find any potential issues, they will refer you to a partner consultant in the appropriate field of specialization. Hope this helps!

  7. My muscle below the side of my knee is very painful, where do i go for treatment. Pls. Help.

  8. Jackie Woochang says

    I think your knee is broke!

  9. Huma sheikh says

    This is Huma sheikh
    My knee is very stiff and very pain full
    My full leg is v painfull
    Vcoz wanes ,scatica pain,,knee pain
    Leg lower side pain
    I already treatment ,,
    Eccupresher treatment
    Plz reply ,

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