The word rectus is a latin word connoting “straight”. Thus the rectus femoris received its name because it runs straight down the thigh.
A short rectus femoris may contribute to a higher positioned patella in relation to the contralateral side. A markedly shortened rectus femoris is suggested by knee flexion of less than 80°or by marked prominence of superior patellar groove
Rectus Femoris originates from anterior inferior iliac spine(AIIS) and the part of alar of ilium superior to the acetabulum
Rectus Femoris together with vastus medialis, vastus lateralis and vastus intermedius joins the quadriceps tendon to insert at the patella and tibial tuberosity (via patellar ligament).
Rectus Femoris is innervated by the femoral nerve, originating from lumbar nerve 2, 3, and 4 nerve roots
Blood is supplied to the Rectus Femoris via descending branch of the lateral circumflex femoral (LCF) artery.
- Rectus Femoris acts with iliopsoas to produce hip flexion especially if the knee is flexed.
- During gait, as a hip flexor, it acts with the iliopsoas in "Toe off" phase,.
- Together with other muscles that are part of the Quadriceps femoris, it facilitates knee extension.
- In terminal swing phase rectus femoris acts as an extensor of the knee, as a muscle in the quadriceps group, it generate force needed for loading(foot flat phase) in stance phase.
- Rectus femoris is more efficient in movement combining hip hyper-extension and knee flexion or from a position of knee extension and hip flexion. For example kicking a soccer ball
Rectus femoris can be palpated as it is the most superior of the quadriceps muscles. Start palpation at AIIS, rectus femoris can be felt until its insertion into the quadriceps tendon. Asking the patient to isometrically contract quadriceps will help to identify the muscle belly.
To assess muscle strength for the Rectus Femoris (including rest of the quadriceps group) position the patient in sitting with the hip and knee flexed to 90° for grade 5, 4 and 3 while grade 2, is assessed in side-lying with test limb uppermost and knee flexed to 90° position.
In Rectus femoris injury :
- FABER (Patrick's test) - illicit no pain
- Pain is felt in resisted hip flexion
- Ely’ test - illicit pain on tightness
- Knee ROM is reduced below 80° in shortness of Rectus femoris or prominence of patella grove is noted.