Rectus Femoris

Origin: Anterior inferior iliac spine (AIIS) of the pelvis.

Insertion: Base of the patella (kneecap) and the tibial tuberosity via the patellar tendon.

Action: The rectus femoris is a two-joint muscle and is involved in both hip flexion and knee extension. It helps to straighten the knee and lift the thigh when walking or running.

Vastus Lateralis

Origin: Greater trochanter of the femur and linea aspera (ridge on the back of the femur).

Insertion: Base of the patella and the tibial tuberosity via the patellar tendon.

Action: The vastus lateralis is responsible for knee extension and stabilizes the patella during leg movements.

Vastus Medialis

Origin: Intertrochanteric line and linea aspera of the femur.

Insertion: Base of the patella and the tibial tuberosity via the patellar tendon.

Action: The vastus medialis helps extend the knee and contributes to patellar stability during movements.

Vastus Intermedius

Origin: Anterior and lateral surfaces of the shaft of the femur.

Insertion: Base of the patella and the tibial tuberosity via the patellar tendon.

Action: The vastus intermedius is involved in knee extension and assists in stabilizing the patella during leg movements.