Muscles of the hip and lower limb

The ischial tuberosity, on the ischium, bears your weight when you sit. The greater trochanter is the bump on the upper outer femur, and the anterior superior iliac spine is the front point of the iliac crest.

• Correct: The ischial tuberosity:
• The greater trochanter:
• The anterior superior iliac spine:

Plantar flexion moves the sole downward, pointing the toes. Dorsiflexion lifts the toes toward the shin, and eversion turns the sole outward.

• Dorsiflexion:
• Correct: Plantar flexion:
• Eversion:

Deep fascia is dense connective tissue beneath the subcutaneous layer that wraps muscles and binds them into groups. The fat under the skin is the subcutaneous tissue, and the endomysium surrounds single fibers.

• A layer of fat under the skin:
• Correct: Dense connective tissue that wraps muscles and holds them in groups:
• The connective tissue around a single muscle fiber:

The rectus femoris runs straight down the middle of the front of the thigh from the ilium to the quadriceps tendon. It is the only part of the quadriceps femoris that crosses the hip.

• Vastus intermedius: The vastus intermedius lies deep, hidden under the rectus femoris.
• Sartorius: The sartorius crosses the thigh diagonally, from the anterior superior iliac spine to the medial tibia.
• Correct: Rectus femoris: Correct. The straight middle muscle is the rectus femoris.
• Vastus lateralis: The vastus lateralis is on the outer side of the thigh.

The biceps femoris is the lateral hamstring. Its long head starts on the ischial tuberosity and its short head on the linea aspera; it inserts on the head of the fibula.

• Semimembranosus: The semimembranosus is a medial hamstring.
• Correct: Biceps femoris: Correct. The lateral hamstring is the biceps femoris.
• Semitendinosus: The semitendinosus is a medial hamstring, with a long cord-like tendon.
• Vastus lateralis: The vastus lateralis is on the outer front of the thigh, part of the quadriceps femoris.

Bleeding and swelling inside the anterior compartment, wrapped in deep fascia that cannot stretch, raise the pressure until blood cannot flow through the capillaries. Pain out of proportion to the injury, and pain when the compartment's muscles are passively stretched (pointing the toes stretches the dorsiflexors), are the early signs. A pulse is often still present.

• Correct: Compartment syndrome of the anterior compartment of the leg: Correct. This is compartment syndrome of the front of the leg.
• Rupture of the calcaneal tendon: A calcaneal tendon rupture causes weakness rising onto the toes and pain at the back of the ankle, not severe pain in the front of the leg.
• A hamstring strain: The hamstrings are on the back of the thigh, not the front of the leg.
• Normal pain after a fracture is set: Pain far worse than expected, and worse when the compartment's muscles are stretched, is not normal. A present pulse does not rule compartment syndrome out: the pressure in the large artery is far higher than the pressure in the compartment, so the pulse is often felt until late.

The quadriceps femoris is four muscles: the rectus femoris and the vastus lateralis, medialis and intermedius. All four insert through the quadriceps tendon, patella and patellar ligament on the tibial tuberosity.

• Correct: Rectus femoris: Yes. The rectus femoris is the one part that crosses the hip.
• Correct: Vastus lateralis: Yes. The vastus lateralis is on the outer thigh.
• Sartorius: No. The sartorius is also in the front of the thigh, but it inserts on the medial tibia and is not part of the quadriceps.
• Correct: Vastus medialis: Yes. The vastus medialis is on the inner thigh above the knee.
• Correct: Vastus intermedius: Yes. The vastus intermedius lies deep under the rectus femoris.
• Biceps femoris: No. The biceps femoris is a hamstring, on the back of the thigh.

Standing on the right leg, the body's weight hangs to the left of the right hip. The right gluteus medius and minimus, abductors of the standing leg, pull the ilium down toward the greater trochanter and hold the pelvis level. When they are weak, the opposite side drops: a positive Trendelenburg sign.

• Left gluteus maximus: The gluteus maximus mainly extends the hip, and the muscle that levels the pelvis belongs to the standing leg, here the right.
• Correct: Right gluteus medius: Correct. The standing leg's gluteus medius holds the pelvis level.
• Right iliopsoas: The iliopsoas flexes the hip; it does not hold the pelvis level in standing.
• Left adductor longus: The adductor longus adducts the thigh and belongs to the lifted leg; it cannot hold up the pelvis on this side.

An infant's thigh muscles are well developed while the gluteal and deltoid muscles are still small, so the middle third of the vastus lateralis on the outer thigh is the preferred site.

• Deltoid site: The deltoid is the usual vaccine site in adults, but in young infants it is too small.
• Dorsogluteal site: The dorsogluteal site is avoided at every age: a large nerve lies close by and the fat layer is thick.
• Correct: Vastus lateralis site: Correct. The vastus lateralis is preferred in infants.
• The gastrocnemius: The calf is not a standard injection site.

The hamstrings insert behind the knee's axis, on the head of the fibula (biceps femoris) and the medial tibia (semitendinosus and semimembranosus). The tibial tuberosity, on the front of the tibia, is where the quadriceps femoris inserts.

• All three originate on the ischial tuberosity: Correct step. The ischial tuberosity is the hamstrings' shared origin.
• They run down the back of the thigh, behind the hip joint: Correct step. Running behind the hip, they extend it.
• They cross behind the knee joint: Correct step. Crossing behind the knee, they flex it.
• Correct: They insert on the tibial tuberosity: This is the wrong step. They insert on the fibula and medial tibia, not the tibial tuberosity.

The fibularis longus and brevis, in the lateral group of the leg, pass behind the lateral malleolus to the foot and turn the sole outward.

• Tibialis anterior and tibialis posterior: Both tibialis muscles invert the foot, turning the sole inward.
• Gastrocnemius and soleus: The gastrocnemius and soleus plantar flex the foot through the calcaneal tendon.
• Correct: Fibularis longus and fibularis brevis: Correct. The fibularis muscles evert the foot.
• Extensor digitorum longus and sartorius: The extensor digitorum longus mainly extends the toes, and the sartorius acts at the hip and knee, not the foot.