Vastus medialis muscle

At a glance

English

Vastus medialis muscle

Latin (TA2)

Musculus vastus medialis

System

Muscle

Region

Lower limb

Side

Paired, left and right

About the vastus medialis muscle

Vastus medialis is the head of quadriceps femoris on the inner side of the thigh. Its lower part forms the rounded, teardrop-shaped swelling just above and medial to the patella, which stands out clearly when the knee is straightened against resistance. Its upper part is thinner and lies partly beneath sartorius, forming part of the outer wall of the adductor canal.

It arises from the lower intertrochanteric line, the spiral line, the medial lip of the linea aspera and the upper medial supracondylar line, as well as from the medial intermuscular septum and the tendons of adductor longus and adductor magnus. Its fibres run downwards and forwards, the lowest almost horizontally. They end on the medial border of the patella and the quadriceps tendon, and some continue as the medial patellar retinaculum to the medial tibial condyle. The near-horizontal lowest bundle is often called vastus medialis obliquus.

Like the other vasti it extends the knee. Its oblique lower fibres also pull the patella inwards, balancing the outward pull of vastus lateralis and the angled line of the quadriceps as a whole, which keeps the kneecap tracking in its groove on the femur. For this reason it is regarded as the main stabiliser of the patella during walking and in the last part of knee extension.

It is supplied by the femoral nerve through a long branch, the nerve to vastus medialis, that runs in the adductor canal, and by branches of the femoral artery and the descending genicular artery. It wastes quickly after knee injury or surgery, and its bulk is checked during rehabilitation. Weakness of its oblique fibres is linked to front-of-knee pain and to lateral dislocation of the patella, so strengthening it is a standard part of treatment.

Attachments, action and supply

Origin

Lower intertrochanteric line, spiral line, medial lip of the linea aspera, medial supracondylar line, medial intermuscular septum and the tendons of adductor longus and magnus.

Insertion

Medial border and base of the patella through the quadriceps tendon, and thence the tibial tuberosity; fibres also form the medial patellar retinaculum.

Action

Extends the knee and holds the patella medially against lateral displacement.

Nerve supply

Femoral nerve (L2, L3, L4), through the nerve to vastus medialis.

Blood supply

Femoral artery, descending genicular artery and the deep femoral artery.