This note records the layering and formal relationships of the lower limb muscles. As with the upper limb there is a lot of material here, so this note will be updated over time and the figures may be redrawn.
The organizing idea of the upper limb is rotation — the radius turning around the ulna, with the whole arm's form changing accordingly. The lower limb has no such freedom; its organizing idea is bearing weight. That difference makes the formal logic of the two completely different: arm muscles are long and slender for mobility, leg muscles are thick for support, and the leg follows a very fixed set of rules you can apply directly.
The hip - femur - [tibia, fibula] axis
Start with the skeleton.
The pelvis is where the lower limb begins. For drawing, three landmarks matter:
- The ASIS (anterior superior iliac spine): the two points you can feel at the sides of the waist. They are the most reliable indicator of which way the pelvis is facing. When drawing the junction of torso and legs, place these two first.
- The iliac crest: the arc sweeping back and up from the ASIS, forming the upper limit of the waist's form.
- The greater trochanter: the large prominence at the outer top of the femur, appearing on the surface as the widest point of the hip. It sits at roughly the same height as the pubis.
The femur is the longest bone in the body. The key point is that it is not vertical: the head sits in the acetabulum, well inboard, while the shaft runs down and outward to the knee. Seen from the front the two femurs form an inverted V. A wider female pelvis makes that angle larger, and this is the most fundamental difference when drawing male and female legs — not the thickness of the leg but the slant of the femur.
The tibia and fibula: the two bones of the lower leg. The tibia is thick, medial, and bears the weight; the fibula is thin, lateral, bears almost nothing and mainly provides muscle attachment. This is completely unlike the radius and ulna — they do not cross or rotate.
The lower leg follows a very useful rule: the medial malleolus is high and the lateral malleolus is low. The medial malleolus is the bottom of the tibia, the lateral one the bottom of the fibula, and since the fibula runs longer the outer ankle sits lower. The same happens at the knee, where the medial femoral condyle sits lower than the lateral. So along the whole leg the inner and outer sides are offset from each other. Show that offset and the leg immediately stops looking stiff.
Gluteus maximus
The gluteus maximus is the thickest muscle in the body.
Origin: back of the ilium, sacrum, coccyx Insertion: the gluteal tuberosity on the back of the femur, and the iliotibial band
When drawing it:
- The lower edge of the gluteus maximus is not the lower edge of the buttock. The horizontal crease underneath is made by skin and fat; the actual lower border of the muscle is a diagonal running from low-inside to high-outside, at a steeper angle than the crease. Drawn as a horizontal line, the buttocks become two bricks.
- There is a depression between its upper outer part and the gluteus medius — the most important structure on the side of the pelvis.
- Most of its fibres insert into the iliotibial band rather than the femur, which means the gluteus maximus actually participates in stabilizing the knee.
Gluteus medius
The gluteus medius sits above and in front of the maximus, appearing on the surface as the mass between the iliac crest and the greater trochanter.
It determines the width of the hips. Standing on one leg, the gluteus medius on the opposite side contracts to keep the pelvis level — the single most important mechanical relationship in a standing pose, and getting it right is what makes a figure actually stand. The pelvis on the relaxed side drops slightly, producing contrapposto.
The thigh: four groups
The thigh muscles divide into four functional groups arranged around the femur. This grouping is far more useful than memorizing them one at a time.
Front: quadriceps
Four muscles: rectus femoris (central, the only one crossing the hip), vastus lateralis, vastus medialis, and vastus intermedius (deep and invisible).
On the surface:
- The three visible muscles converge above the knee onto the patella, which connects through the patellar ligament to the tibial tuberosity.
- The vastus medialis ends noticeably lower than the vastus lateralis, pressing almost down onto the knee. This is the most recognizable rule on the thigh and the key check on whether a leg is drawn correctly. Drawing the two sides symmetrically robs the leg of its character.
- The vastus lateralis has its upper half covered by the iliotibial band, so its surface bulge appears lower than the muscle itself.
Back: hamstrings
Three muscles: biceps femoris (lateral), semitendinosus and semimembranosus (medial).
They leave the ischial tuberosity and divide into an inner and an outer band, passing behind the knee to the tibia and fibula respectively. The diamond-shaped hollow behind the knee — the popliteal fossa — is enclosed by those two bands and the gastrocnemius below. With the knee flexed, the tendons on both sides stand out as two distinct cords, which must be shown when drawing seated and crouching poses.
Medial: the adductors
Pectineus, adductor longus, adductor magnus, gracilis and others, running from the pubis to the medial femur.
For drawing, this group can be summarized as a single triangular plane spreading down and outward from the pubis. Subdividing it gains little, but its presence is what makes the inner thigh a tapering transition rather than a straight line.
Lateral: the iliotibial band
Strictly not a muscle but a thick aponeurosis running from the iliac crest down to the lateral tibia.
It is what decides the outer contour of the thigh. Part of the gluteus maximus and the tensor fasciae latae insert into it, and when taut the outer thigh shows a straight or even slightly concave edge — which is why an athlete's outer thigh is frequently not a convex curve but flattened through the middle. Beginners habitually draw the outer thigh as a full arc, and it is a very common error.
The lower leg
Gastrocnemius
The most conspicuous muscle at the back of the lower leg, with two heads both originating at the bottom of the femur and merging into the Achilles tendon.
It follows the same rule as the thigh: the medial head is lower and larger than the lateral head. Seen from behind, the inner and outer contours of the calf are therefore offset — the inner bulge low, the outer high. This rule, the vastus medialis on the thigh, and the ankle malleoli all belong to one system, and together they give the whole leg its zigzag rhythm.
The single most useful piece of experience for drawing legs is this alternating rhythm: outer thigh high (ITB / vastus lateralis) → inner thigh low (vastus medialis) → outer calf high → inner calf low → medial malleolus high, lateral malleolus low. The leg is a chain of alternating arcs, not two parallel lines.
Soleus
Underneath the gastrocnemius, visible on the surface only along either side of it. It is wider than the gastrocnemius, so the widest part of the calf is actually the two of them combined. From the side, the soleus shows as a band emerging below the outer edge of the gastrocnemius.
Tibialis anterior
On the front and outside of the lower leg. Note that the front edge of the tibia lies directly under the skin — the shin, hard bone to the touch. So the front of the lower leg is not a centred ridge but rather: the sharp bony edge slightly to the inside, with the muscle bulge just outside it. Get this wrong and the calf becomes a cylinder.
The Achilles tendon
Narrowing down from below the calf and inserting on the calcaneus. It is the thickest tendon in the body and very visible on the surface; from the side it is the sharply tapering line between calf and ankle.
There is a hollow on either side of it, and those two hollows plus the height difference between the malleoli are the whole structure of the ankle.
Summary
The lower limb compresses into three rules:
- The femur slants. From the outer hip down and inward to the knee, at a different angle in men and women.
- Inside and outside are offset. Inner thigh low, inner calf low, medial malleolus high — the leg is a chain of alternating arcs.
- The outside is flat. The iliotibial band keeps the outer thigh close to a straight line; do not draw it as a full arc.
Get those three right and the leg gains its volume and its weight. The head, neck, hands and feet will follow in this series.