A 34-year-old woman comes to the physician complaining of easy fatigability. She lives alone and works as an accountant. Her menstrual cycles are regular and her last menstrual period was 2 weeks ago. She does not smoke or consume alcohol. Her blood pressure is 150/90 mm Hg and pulse is 82/min. During her physical examination, she sits up from the supine position without using her hands. Which of the following muscles contributes most to the described movement?
| Major muscles responsible for motion at the hip | |||
| Flexion | Extension | Abduction | Adduction |
| • Iliopsoas • Rectus femoris • Tensor fascia lata | • Gluteus maximus • Semitendinosus • Semimembranosus • Biceps femoris - long head | • Gluteus medius • Gluteus minimus | • Adductor brevis • Adductor longus • Adductor magnus |
Major muscles used when sitting up from the supine position include the external abdominal obliques, the rectus abdominis, and the hip flexors. The psoas major and iliacus contribute most significantly to the hip flexion; they, along with the psoas minor, are collectively known as the iliopsoas. The capacity of these muscles to carry out this motion can be deduced from the fact that they originate on the pelvis and spinal column, cross the hip joint, and insert on the femur.
The psoas major muscle arises from the bodies and intervertebral discs of the inferior-most thoracic and all of the lumbar vertebrae. The iliacus originates from the iliac fossa, a large concave surface found on the inner aspect of the ilium. Both muscles insert via the common iliopsoas tendon into the lesser trochanter of the femur.
(Choice A) The adductor portion of the adductor magnus originates from the inferior ramus of the ischium and inserts into the proximal two-thirds of the posteromedial femur. It is a powerful adductor of the thigh.
(Choice B) The long head of the biceps femoris originates from the ischial tuberosity and inserts into the lateral head of the fibula; it functions as a thigh extensor and leg flexor.
(Choice C) The gluteus medius abducts the femur and is important in keeping the hip level during gait when the body's weight rests on one leg.
(Choice D) The obturator externus arises from the anteromedial surface of the obturator foramen and inserts near the greater trochanter of the femur. This muscle is a lateral rotator of the thigh.
(Choice F) The vastus medialis is a component of the quadriceps femoris. It arises from the proximal femur and ultimately inserts into the tibial tuberosity by means of the patella. It functions as a knee extensor.
Educational objective:
Muscles used when sitting up from the supine position include the external abdominal obliques, the rectus abdominis, and the hip flexors. The iliopsoas muscle is the most important of the hip flexors and includes the psoas major, psoas minor, and iliacus. The rectus femoris, sartorius, tensor fascia lata, and the medial compartment of the thigh also contribute to hip flexion.