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Structure
Beginner
8 min read

Calves

The calf brings together the gastrocnemius and the soleus, which share the calcaneal tendon. They push the foot downward, and one of the two also depends on the position of the knee.
3D scene
The calves during a squat
The scene shows the leg during the descent of a squat. The tibia tips forward and the calf lengthens while braking that movement, without the heel leaving the ground. Without the 3D, the idea is that these muscles link the knee and the leg to the heel, and that they set how far the tibia leans over the foot.
Open in the explorer

Where the calf muscles are located

The calf is made of two stacked muscles that meet on a common tendon, the thickest in the human body. The gastrocnemius is superficial and draws the visible relief; the soleus, wider and deeper, shows on either side of it. Together they are often described under the name triceps surae, to which the plantaris is added when it is present.

The gastrocnemius

It arises by two heads sitting above the knee: the medial head from the back surface of the medial condyle of the femur, the lateral head from the outer surface of the lateral condyle. Because its origins are on the femur, this muscle crosses both the knee and the ankle.

The soleus

It arises from the back surface of the head and of the upper third of the fibula, as well as from the soleal line on the tibia. It crosses the ankle only, and how it works therefore does not depend on the position of the knee.

Common insertion

The two muscles converge on the calcaneal tendon, also called the Achilles tendon, which attaches to the back surface of the calcaneus, the heel bone.

Innervation and palpable landmarks

Innervation comes from the tibial nerve, from roots S1 and S2. The calcaneal tendon is felt immediately above the heel; the two heads of the gastrocnemius stand out when rising onto the toes, and the soleus shows on the sides of the calf, below the relief of the gastrocnemius.

What the calf muscles do

  • Plantar flexion of the ankle: they pull the heel upward, which pushes the front of the foot downward. This is the movement of rising onto the toes and of push-off in walking.
  • Knee flexion: the gastrocnemius, because it arises from the femur, takes part in this action.
  • Holding an upright stance: the soleus works continuously to keep the tibia from tipping forward over the foot.
  • Assisting venous return: repeated contraction of the calf compresses the deep veins and helps blood travel back toward the heart.
Plantar flexion
Movement that takes the front of the foot away from the tibia, as when rising onto the toes. The opposite movement, which brings the top of the foot toward the tibia, is called dorsiflexion.
ankle extension
Certainty level · Established
The position of the knee changes the length of the gastrocnemius, but not that of the soleus.
The gastrocnemius crosses two joints: with the knee bent, it is shortened and its ability to produce tension at the ankle falls. The soleus, which crosses the ankle only, is unaffected. This difference is described in kinesiology textbooks and is consistent with moment-of-force measurements taken at different knee angles. It explains why plantar flexion with a straight knee and plantar flexion with a bent knee do not load the two muscles in the same proportions.
Standring S (2020) · Neumann DA (2016)

Seeing the calves in motion

The calves during a squat

The scene shows the leg during the descent of a squat. The tibia tips forward and the calf lengthens while braking that movement, without the heel leaving the ground. Without the 3D, the idea is that these muscles link the knee and the leg to the heel, and that they set how far the tibia leans over the foot.
Current step
Three segments, three joints
The squat is not a thigh movement: it is a sequence. Pelvis, femur and tibia form three segments linked by the hip, the knee and the ankle, with the patella sitting in front of the knee. The whole mechanics of the movement lives in those pivots.
Scene description
A three-dimensional diagram of the lower half of the body, standing, seen from the front: pelvis, femurs, tibias and patellae are shown in bone tones, with the feet and a reference trunk in a neutral paper shade. On each thigh the four heads of the quadriceps are laid over in terracotta and stay distinct: rectus femoris in the middle, vastus lateralis on the outside, vastus medialis on the inside, and the deeper vastus intermedius against the femur. Behind, the glutes cap the pelvis and the calves fill the upper shank. A three-second animation flexes the ankle, knee and hip together: the knee travels forward over the foot, the hip moves back and down, the trunk leans, and then the movement reverses. The volumes are stylised: this is a teaching diagram, not an exact anatomical reconstruction.
Visible structures
  • Rectus femoris
    The only head of the quadriceps to cross two joints: it arises from the anterior inferior iliac spine of the pelvis and runs down the middle of the thigh into the quadriceps tendon. It extends the knee and flexes the hip.
  • Vastus lateralis
    The largest of the four heads, arising from the greater trochanter and the linea aspera on the outer side of the femur. It acts on the knee alone, extending it, and gives the thigh its outer contour.
  • Vastus medialis
    The inner head, arising from the linea aspera of the femur, whose lowest fibres reach the patella almost horizontally. It extends the knee and helps keep the patella tracking in line.
  • Vastus intermedius
    The deep head, pressed against the front of the femur and covered by the other three. Invisible from the outside, it still produces a substantial share of knee extension.
  • Patella
    A sesamoid bone embedded in the quadriceps tendon, which continues as the patellar tendon onto the tibial tuberosity. By holding the tendon away from the knee axis, it increases the lever arm of the quadriceps.
  • Glutes
    Arising from the iliac wing and the sacrum, inserting on the femur and the iliotibial tract. In the squat they extend the hip: the more the trunk leans forward, the larger their share of the work compared with the quadriceps.
  • Calves
    The gastrocnemius and soleus, joining on the calcaneus through the Achilles tendon. In the squat they work mostly as brakes, controlling ankle dorsiflexion and therefore how far the knee travels forward.
Guided steps
  • 1/5
    The squat is not a thigh movement: it is a sequence. Pelvis, femur and tibia form three segments linked by the hip, the knee and the ankle, with the patella sitting in front of the knee. The whole mechanics of the movement lives in those pivots.
  • 2/5
    Rectus femoris occupies the middle of the thigh, vastus lateralis its outer border, vastus medialis its inner border, and vastus intermedius hides beneath them against the femur. All four converge on a single tendon: they pull together, but only rectus femoris also crosses the hip.
  • 3/5
    The quadriceps tendon wraps around the patella and continues to the tibial tuberosity. By holding the tendon away from the axis of flexion, the patella lengthens the lever arm — that is what makes knee extension effective in the bottom position.
  • 4/5
    Ankle, knee and hip flex together. The ankle lets the knee travel forward over the foot, the femur tips backwards, and the trunk leans to keep balance over the midfoot. The quadriceps first brakes the descent, then drives the way back up.
  • 5/5
    The glutes extend the hip and take on more work the further the trunk leans; the calves restrain the ankle and steady the base. The quadriceps is the most heavily loaded engine in the squat, but it does not decide the depth reached on its own.
Model licence · Z-Anatomy et BodyParts3D — CC-BY-SA 4.0

The movements they take part in

The calf muscles are involved in the squat without being its drivers: they control how far the tibia travels forward and keep the foot in contact with the ground while the quadriceps and the glutes produce the movement.
They also work in the hip hinge, where they steady the ankle as the pelvis travels back. Their most direct demand remains walking, running and jumping, where plantar flexion supplies the push-off.

Synergists

  • The tibialis posterior, the fibularis longus and the flexor hallucis longus complete plantar flexion at depth.
  • The hamstrings accompany the gastrocnemius in knee flexion.
  • The quadriceps controls the knee while the calf controls the ankle.

Antagonists

  • The tibialis anterior lifts the front of the foot, the opposite action to plantar flexion.
  • The extensor digitorum longus and the fibularis tertius assist that dorsiflexion.

What the 3D model simplifies

Limit
Two stacked muscles, a single outline
The scene shows the soleus in its entirety, whereas it is largely hidden by the gastrocnemius. What is seen and felt on a calf therefore does not match what the model displays.
The plantaris, present in only part of the population, is not represented, and neither are the deep muscles of the leg. The height at which the muscle belly continues into tendon varies widely from person to person: it is one of the factors that explain differences in calf shape, independently of any training.

Sources

Key sources

  • Standring S (2020). Gray's Anatomy: The Anatomical Basis of Clinical Practice, 42nd edition. Elsevier.
  • Neumann DA (2016). Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation, 3rd edition. Elsevier.
Put it into practice in Shapier

Train the calves with calf raises

Practising calf raises, knee straight or bent, is done in Shapier; Body Lab only explains why knee position matters.
Train the calves with calf raises
Body Lab explains; Shapier lets you act and track.

Check my understanding

Why does knee position change how the work is shared between the gastrocnemius and the soleus?
What role do the calves play during a squat?
Why does calf shape vary from person to person, independently of any training?
Choose an answer

Read next

  • Tibialis anterior
    Tibialis anterior runs down the front of the shin and lifts the foot. Quiet under load, it works on every step to keep the toes from dragging on the ground.
    With a 3D scene
  • Quadriceps
    The quadriceps brings together four muscles on the front of the thigh that share a common tendon. It extends the knee, and one of its heads also crosses the hip.
    With a 3D scene
  • Hamstrings
    The hamstrings occupy the back of the thigh. They extend the hip and flex the knee, and their length depends on the combined position of these two joints.
    With a 3D scene

Where to go next

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Trust and method

Author
equipe-editoriale-shapier
Editorial review
Thanh Chau
Scientific review
Pending
Published on
August 2, 2026
Reviewed on August 2, 2026
Next review due August 2, 2027
Limits of this page
  • The soleus is largely covered by the gastrocnemius; the scene displays it whole, which does not match what can be seen or felt.
  • The plantaris muscle, inconstant in humans, is not represented in the model.
  • The deep muscles of the back compartment of the leg, which also contribute to plantar flexion, are not drawn separately.
Sources
  • Standring S (2020). Gray's Anatomy: The Anatomical Basis of Clinical Practice, 42nd edition. Elsevier.
  • Neumann DA (2016). Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation, 3rd edition. Elsevier.
Educational content. Body Lab does not diagnose and does not replace professional advice.
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