Overview
Its four heads converge on the patella: rectus femoris, vastus lateralis, vastus medialis and vastus intermedius. The model shows the first three; the vastus intermedius lies deep, on the cranial surface of the femur.
Origin
- Rectus femoris (m. rectus femoris): body of the ilium, cranial to the acetabulum. The only head that crosses the hip.
- Vasti (m. vastus lateralis, medialis, intermedius): proximal femur.
Insertion
Tibial tuberosity, through the patella and the patellar ligament.
Action
Extends the stifle. The rectus femoris also flexes the hip.
Innervation
Femoral nerve (n. femoralis).
Clinical relevance
- Tapping the patellar ligament extends the stifle: the patellar reflex tests the femoral nerve and spinal cord segments L4–L6.
- Its craniolateral mass is a common intramuscular injection site.
- After distal femoral fractures in puppies, quadriceps contracture can lock the stifle in extension.