The vastus intermedius is the deepest quadriceps muscle, lying directly on the femoral shaft deep to the rectus femoris. It inserts into the deepest layer of the quadriceps tendon. The articularis genu — a small separate muscle slip from the deep VI surface — pulls the suprapatellar pouch upward during knee extension to prevent impingement. VI tears after femoral fracture produce the thick myofascial adhesions (suprapatellar and lateral gutters) that cause post-fracture knee stiffness.
| Origin | Anterior and lateral femoral shaft (upper two-thirds) — deep to the rectus femoris |
|---|---|
| Insertion | Deep layer of the quadriceps tendon and superior patellar base |
| Nerve Supply | Femoral nerve (L2, L3, L4) |
| Blood Supply | Lateral circumflex femoral artery |
| Actions | Knee extension (deepest quadriceps — direct force transmission to the patella through the deep quadriceps layer) |
|---|
Vastus intermedius adhesion to the femoral shaft after femoral fracture ORIF produces severe knee stiffness from suprapatellar pouch obliteration. Arthroscopic lysis of VI adhesions and suprapatellar pouch release combined with aggressive physiotherapy restores motion. Continuous passive motion (CPM) in the early post-operative period reduces VI adhesion formation.
The vastus intermedius is not palpable on the surface due to its deep position under the rectus femoris — it is assessed on cross-sectional imaging as the deepest quadriceps layer.
Post-fracture VI adhesion to the femoral shaft producing severe knee stiffness managed with arthroscopic adhesiolysis and aggressive rehabilitation.
