Vastus intermedius
The quadriceps head you will never see, lying directly on the femur beneath the other three.
- Type
- Muscle
- Region
- Thigh
- Standard name
- m. vastus intermedius
- Origin
- Anterior and lateral surfaces of the upper two-thirds of the shaft of the femur
- Insertion
- Deep surface of the quadriceps tendon, then the patella and the tibial tuberosity
- Actions
- knee extension
- Verify
- TA2 2619 TA98 A04.7.02.022
What it is
The deepest of the four quadriceps, lying flat against the front of the femur with rectus femoris covering it and the two other vasti on either side. It arises directly from the bone and blends into the deep surface of the quadriceps tendon.
It is invisible and impalpable. Nothing you can see or feel on the front of your thigh is this muscle.
Beneath its lowest fibres sits a small separate muscle, articularis genus, which attaches to the capsule of the knee joint and pulls it clear as the knee straightens — a housekeeping muscle that stops the capsule being pinched.
What it does
Extends the knee. One joint, one action, no complications.
What loads it
Everything that loads the quadriceps, in the same proportion. The goblet squat and box squat load it as part of the group.
What is commonly got wrong about it
That it can be targeted. It is under three other muscles doing the same job across the same joint. There is no exercise, foot position or knee angle that gets at it selectively, and nothing that claims to can be verified by anything you would feel.
That "quad thickness" is trainable separately from the rest. This muscle contributes real volume to the thigh and it grows when the quadriceps are trained. It does not grow on its own schedule.