CorpusHuman Anatomy
MuscularMuscle group

Quadriceps femoris

Musculus quadriceps femoris

Also known as: quads, quadriceps, quadriceps tendon, knee extensors

The great extensor of the knee: rectus femoris and the three vasti. Their common tendon contains the patella and continues as the patellar ligament to the tibial tuberosity.

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Overview

Quadriceps femoris forms the bulk of the front of the thigh. Rectus femoris arises from the pelvis and crosses both hip and knee. Vastus lateralis, vastus medialis and vastus intermedius arise from the femur and cross only the knee. The four converge on the quadriceps tendon, which encloses the patella, the largest sesamoid bone. Below the patella the tendon continues as the patellar ligament to the tibial tuberosity. Expansions from the vasti (the medial and lateral patellar retinacula) reinforce the knee capsule. A small slip from the vastus intermedius, articularis genus, pulls the suprapatellar bursa upward during extension.

The quadriceps is the only extensor of the knee and is essential for standing up, climbing, jumping and kicking. Its eccentric action controls descent (sitting down, going downstairs) and absorbs shock at heel strike. The patella increases its lever arm by up to ≈30%. All four parts are supplied by the femoral nerve (L2–L4). The patellar (knee-jerk) reflex tests L3–L4.

Location

Anterior compartment of the thigh.

Parts & subdivisions

  1. Rectus femoris
    AIIS and ilium above the acetabulum. Crosses the hip and knee.
  2. Vastus lateralis
    The largest part. Greater trochanter and lateral lip of the linea aspera.
  3. Vastus medialis
    Intertrochanteric line and medial lip of the linea aspera. Its oblique fibres (VMO) stabilise the patella.
  4. Vastus intermedius
    Anterior and lateral surfaces of the femoral shaft, deep to rectus femoris.
  5. Patellar ligament
    Continuation of the quadriceps tendon from the patella to the tibial tuberosity.

Anatomy

Origin

Rectus femoris: anterior inferior iliac spine and the ilium above the acetabulum. Vasti: the femoral shaft (see each part).

Insertion

Base of the patella via the quadriceps tendon, then the tibial tuberosity via the patellar ligament.

Action

Extension of the leg at the knee; rectus femoris also flexes the thigh at the hip.

Innervation

Femoral nerve.

Nerve roots

L2–L4

Arterial supply

Lateral circumflex femoral artery (descending branch); profunda femoris and femoral arteries; descending genicular artery.

Function

  • Extends the knee (the sole knee extensor)
  • Rectus femoris also flexes the hip
  • Controls knee flexion eccentrically and absorbs shock
  • Stabilises the patella and the knee

Clinical significance

Patellar reflex

Tapping the patellar ligament stretches quadriceps spindles and produces knee extension (L3–L4, femoral nerve). It is lost in L4 radiculopathy and femoral neuropathy (e.g. diabetic amyotrophy).

Quadriceps wasting

The quadriceps atrophies within days of knee injury or immobilisation (arthrogenic muscle inhibition), especially VMO. Rehabilitation focuses on restoring it.

Extensor mechanism rupture

Quadriceps tendon rupture (in older people, often with diabetes, renal failure or steroid use) or patellar ligament rupture (younger athletes) causes inability to straight-leg raise and a palpable gap.

Mnemonics

Knee jerk roots

"L3–4, kick the door."

Compiled from standard anatomy and physiology references — see the Muscular System sources. For education only; not medical advice.