Vastus medialis
The inner quadriceps, and the subject of the most durable disputed claim in lower-limb training.
- Type
- Muscle
- Region
- Thigh
- Standard name
- m. vastus medialis
- Origin
- Intertrochanteric line and the medial lip of the linea aspera of the femur
- Insertion
- Medial border of the patella, then the tibial tuberosity via the patellar ligament
- Actions
- knee extension
- Verify
- TA2 2620 TA98 A04.7.02.023
What it is
The head of the quadriceps on the inner thigh, arising along the inner ridge of the femur and inserting on the inner border of the patella. Its lowest fibres run almost horizontally across to the kneecap, which is unusual — the rest of the quadriceps pull roughly vertically.
Those low, near-horizontal fibres are often labelled separately as VMO, the vastus medialis obliquus. Whether VMO is a genuinely distinct muscle with its own nerve supply, or simply the lower part of one muscle with a different fibre angle, has been argued for a long time and is not settled.
What it does
Extends the knee, in company with the other three heads.
Its distinctive contribution is directional rather than a separate action: its inward pull opposes the outward pull of vastus lateralis, and that balance is part of what keeps the patella centred in its groove as the knee bends and straightens.
What loads it
The same movements that load the rest of the quadriceps. The goblet squat and box squat load it throughout.
What is commonly got wrong about it
This muscle carries the single most persistent disputed claim in lower-limb training, so it is worth setting out carefully.
The claim. The VMO is weak or fires late; this lets the patella drift outward; that causes pain at the front of the knee; therefore the VMO should be trained selectively, using terminal knee extensions, short-arc movements, or a ball squeezed between the knees.
What is reasonably well supported. The muscle pulls the patella medially. Patellar tracking is a real mechanical phenomenon. Pain at the front of the knee is extremely common.
What is not. That you can preferentially recruit this part of the quadriceps by choosing an exercise or a knee angle — this is the weak link, and attempts to demonstrate it have produced inconsistent results. Also unsupported is the leap from tracking to pain as a settled causal chain; anterior knee pain is multifactorial and poorly understood, and it is exactly the sort of thing to have looked at rather than self-managed from a website.
What follows. Training the quadriceps strengthens this muscle along with the rest. That is the access you have. Claims to do more than that are ahead of the evidence.
"Teardrop" as an aesthetic target is the same claim wearing different clothes, and the shape of the lower inner thigh is mostly attachment anatomy.