Knee joint

Vastus Lateralis / Vastus Intermedius / Vastus Medialis / Popliteus
Vastus Lateralis Muscle
Vastus Lateralis is the most lateral (outside) of the four quadriceps muscles. It is thought to be a
major contributor to patella tracking injuries.
Origin

Outer surface of the greater trochanter of the femur

Upper half of the linea aspera
Insertion

Patella via the quadriceps tendon and then the tibial tuberosity via the patella tendon
Actions

Knee extension
Innervation

Femoral nerve
Daily uses

Cycling

Walking up stairs
Vastus Intermedius Muscle
Vastus Intermedius is located deep to the Rectus Femoris muscle and is part of the quadriceps
muscle group.
Origin

Anterior and lateral surfaces of the shaft of the femur
Insertion

Patella via the quadriceps tendon and then the tibial tuberosity via the patella tendon
Actions

Knee extension
Innervation

Femoral nerve
Daily uses

Cycling

Walking up stairs
Vastus Medialis Muscle
Vastus Medialis is the most medially located of the quadricep muscles and is thought to be
important in stabilizing the knee cap or patella.
Origin

Intertrochanteric line (between the greater and lesser trochanters of the femur)

Medial lip of the linea aspera of the femur
Insertion

Patella via the quadriceps tendon and then the tibial tuberosity via the patella tendon
Actions

Knee extension
Innervation

Femoral nerve
Daily uses

Cycling

Walking up stairs
Popliteus
Popliteus is a small muscle which is often described as the key of the knee joint. It unlocks the knee
joint by rotating the femur at the beginning of knee flexion to allow full knee flexion to occur.
Origin

Lateral condyle of the femur
Insertion

Upper posterior surface of the tibia, above the soleal (popliteal) line
Actions

Knee flexion

Internal rotation of the knee when it is flexed
Innervation

Tibial nerve
Daily uses

Walking