Vastus medialis (oblique) (VMO)…part 12 of the grumbly muscle blog…

So…whats a VMO?

Its one of your quad muscles and sits the inside of your thigh and knee. It’s been described as having two distinct portions: Vastus medialis ‘longus’ (upper part) and the vastus medialis ‘oblique’, the teardrop shaped portion of the muscle on the inside of the knee (lower part). We tend to concentrate on the oblique portion of the muscle because it has double the nerve innervation, different muscle structure and produces more electrical activity than the ‘longus’ part.

What does it do?

  • It helps keep the kneecap ‘on its runner’ and can prevent patella maltracking during knee movements.
  • It is integral to the ‘screw home’ (the knee’s lock-out mechanism) mechanism with help from another quad muscle called vastus lateralis (the one on the outside).
  • Is active throughout knee extension especially the last 15-20 degrees.
  • It helps the other three quads to perform knee extension.
  • Prevents damage to the articular cartilage and subsequent osteoarthritis of the patella and femur and tibia.


It comes from the medial lip if the linea aspera on the inside of the femur.

It joins the quadriceps tendon above the patella (kneecap) and then travels over the knee to insert into a bony protrusion on the centre top of the tibia called the tibial tuberosity.

What happens when it gets grumbly?

Anterior knee pain, patellofemoral pain syndrome (PFPS)  or patella tendinopathy.  If biomechanics of the hip and therefore the knee are ‘off’ it can struggle keeping the kneecap on its track, called the trochlea grove. Why? – Mostly due to a hip muscle called tensor fascia latae (TFL) which feeds into the IT band, which feeds into the ‘retinaculum’ around the kneecap before it inserts onto the head of fibula and Gerdy’s tubercle on the tibia. If the TFL is tight it can shorten, pulling from its origin at the hip, acting upon the knee and the knee cap.

What can we do about it?

We take a two-pronged approach…Restore biomechanics of the hip whilst addressing weakness of this muscle at the knee.

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