Rectus femoris and the vastus lateralis, medialis and intermedius
Mnemonic
Four muscles, one tendon, one nerve:
- Rectus femoris - from the anterior inferior iliac spine, so the only one crossing the hip and therefore the only hip flexor of the group
- Vastus lateralis
- Vastus medialis - its oblique fibres stabilise the patella medially
- Vastus intermedius
All are supplied by the femoral nerve (L2, L3, L4), and all insert into the patella and thence to the tibial tuberosity via the patellar tendon.
“Only rectus femoris crosses two joints”, which is why it is tested with the hip extended and why it is the part most often strained in kicking sports.
Vastus medialis obliquus wastes first and fastest in knee pathology, which is why measuring thigh circumference 20 cm above the tibial tuberosity is part of a knee examination.
The extensor mechanism is tested by a straight leg raise: an extensor lag indicates rupture of the quadriceps or patellar tendon, or a patellar fracture.
Expansion
- Rectus femoris
- Vastus lateralis
- Vastus medialis
- Vastus intermedius
All four are supplied by the femoral nerve and insert via the patellar tendon into the tibial tuberosity to extend the knee.