Vastus intermedius muscle

At a glance

English

Vastus intermedius muscle

Latin (TA2)

Musculus vastus intermedius

System

Muscle

Region

Lower limb

Side

Paired, left and right

About the vastus intermedius muscle

Vastus intermedius is one of the four heads of quadriceps femoris, the great knee extensor of the anterior thigh, and is the deepest of the four, lying directly on the femur, flanked by vastus lateralis and vastus medialis and hidden beneath rectus femoris, so it cannot be seen until rectus is lifted away. Its borders blend so closely with the two other vasti that it is often hard to separate from them.

It arises from the front and lateral surfaces of the upper two-thirds of the femoral shaft and from the lower part of the lateral intermuscular septum. Its fibres run down to a flat aponeurosis on its front surface, which forms the deepest layer of the quadriceps tendon. That tendon attaches to the base of the patella, and the pull continues through the patellar ligament to the tibial tuberosity. Below the muscle, a few fibres from the front of the lower femur form articularis genus, which is often treated as a detached part of vastus intermedius.

Like the other vasti, it crosses only the knee, so it is a pure extensor of the knee joint whatever the position of the hip. It is active whenever the knee is straightened against load, as in rising from a chair, climbing stairs, jumping and squatting, and it works eccentrically to control bending when descending. Articularis genus pulls the suprapatellar bursa upwards as the knee extends so that it is not pinched.

All parts of quadriceps are supplied by the femoral nerve, and vastus intermedius receives its own branches from it. Blood comes from the lateral circumflex femoral artery, especially its descending branch, and from the deep femoral artery. Because it lies on the bone, it is a frequent site of bruising from a direct blow to the front of the thigh, and bleeding deep within it may later calcify, a condition called myositis ossificans.

Attachments, action and supply

Origin

Anterior and lateral surfaces of the upper two-thirds of the femoral shaft and the lateral intermuscular septum.

Insertion

Base of the patella through the deep layer of the quadriceps tendon, and thence the tibial tuberosity via the patellar ligament.

Action

Extends the knee.

Nerve supply

Femoral nerve (L2, L3, L4).

Blood supply

Lateral circumflex femoral artery and the deep femoral artery.