A 65-year-old man is referred by his primary care provider to a neurologist for leg pain. He reports a 6-month history of progressive bilateral lower extremity pain that is worse in his left leg. The pain is 5/10 in severity at its worst and is described as a "burning" pain. He has noticed that the pain is acutely worse when he walks downhill. He has started riding his stationary bike more often as it relieves his pain. His past medical history is notable for hypertension, diabetes mellitus, and a prior myocardial infarction. He also sustained a distal radius fracture the previous year after falling on his outstretched hand. He takes aspirin, atorvastatin, metformin, glyburide, enalapril, and metoprolol. He has a 30-pack-year smoking history and drinks 2-3 glasses of wine with dinner every night. His temperature is 99°F (37.2°C), blood pressure is 145/85 mmHg, pulse is 91/min, and respirations are 18/min. On exam, he is well-appearing and in no acute distress. A straight leg raise is negative. A valsalva maneuver does not worsen his pain. Which of the following is the most appropriate test to confirm this patient's diagnosis?

Computerized tomography myelography

A 48-year-old male presents to his primary care provider with a two-week history of low back pain and left leg pain. He reports that his symptoms started while he was working at his job as a construction worker. He has since experienced intermittent achy pain over his lumbar spine. He has also noticed pain radiating into his left leg and weakness in left ankle dorsiflexion. On exam, he demonstrates the following findings on strength testing of the left leg: 5/5 in knee extension, 4/5 in ankle dorsiflexion, 4/5 in great toe extension, 5/5 in ankle plantarflexion, and 5/5 in great toe flexion. The patellar reflexes are 5/5 bilaterally. He is able to toe walk but has difficulty with heel walking. Weakness in which of the following compartments of the leg is most likely causing this patient’s foot drop?

Superficial posterior compartment

A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?

"Can you tell me more about the symptoms you have been experiencing?"

"Does the diarrhea typically precede the constipation, or vice-versa?"

"Is the diarrhea foul-smelling?"

"Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life"

"Are the symptoms worse in the morning or at night?"

A 45-year-old man is brought to the emergency department following a motor vehicle collision. He reports right hip pain and numbness along the right thigh. Physical examination shows decreased sensation to light touch over a small area of the proximal medial thigh. X-rays of the pelvis show a displaced pelvic ring fracture. Further evaluation of this patient is most likely to show which of the following findings?

Sensory deficit of the dorsal foot

A 32-year-old man comes to the physician because of a 1-month history of intermittent tingling of his hand. He is an avid cyclist and has recently started training for a cycle marathon. Physical examination shows decreased grip strength in the right hand and wasting of the hypothenar eminence. On asking the patient to grasp a piece of paper between his right thumb and right index finger in the first web space, there is hyperflexion of the right thumb interphalangeal joint. Which of the following additional findings is most likely in this patient?

Inability to extend the little finger at the proximal interphalangeal joints

Loss of sensation over the dorsum of the medial half of the hand

Inability to extend the ring finger at the metacarpophalangeal joint

Inability to flex the index finger at the interphalangeal joints

Loss of sensation over the palmar aspect of the middle finger

Muscles and movements of lower limb for USMLE Step 2 CK: High-Yield Anatomy Lessons

Gluteal & Posterior Thigh - Glutes & Hammies

Muscle	Origin	Insertion	Innervation	Main Action(s)
Gluteus Maximus	Ilium, sacrum, coccyx	Gluteal tuberosity, IT band	Inferior gluteal n.	Major thigh extensor; lateral rotation
Gluteus Medius & Minimus	Ilium (external surface)	Greater trochanter	Superior gluteal n.	Abduct & medially rotate thigh; stabilize pelvis
Tensor Fasciae Latae	ASIS	Iliotibial (IT) band	Superior gluteal n.	Flexes, abducts thigh
Hamstrings (Biceps Femoris, Semitendinosus, Semimembranosus)	Ischial tuberosity	Tibia & fibula	Sciatic n.	Extend thigh, flex leg

⭐ The sciatic nerve typically emerges inferior to the piriformis muscle. A superiorly displaced injection into the gluteal region can damage it.

📌 Mnemonic: 'Trendelenburg's sign is a pain in the butt to remember, but it's all about the standing leg's gluteus medius and minimus.'

Anterior & Medial Thigh - Quads & Co.

Anterior and medial thigh muscles with innervation

Muscle	Compartment	Innervation	Main Action(s)
Iliopsoas	Anterior	Femoral n. (L2-L4)	Chief hip flexor
Sartorius	Anterior	Femoral n. (L2-L4)	Flexes, abducts, lat. rotates thigh
Quadriceps Femoris	Anterior	Femoral n. (L2-L4)	Extends knee
Rectus Femoris			Also flexes hip
Adductors (Magnus, Longus, Brevis)	Medial	Obturator n. (L2-L4)	Adducts thigh
Pectineus	Medial	Femoral & Obturator n.	Adducts & flexes thigh
Gracilis	Medial	Obturator n. (L2-L4)	Adducts thigh, flexes knee

⭐ The femoral nerve (L2-L4) innervates the quadriceps. A nerve block here is common for knee surgery.

Anterior & Lateral Leg - Foot Off the Gas

Leg compartments, muscles, and common peroneal nerve

Compartment	Muscles	Innervation	Main Action(s)
Anterior	Tibialis Anterior, Extensor Hallucis Longus, Extensor Digitorum Longus	Deep Peroneal (Fibular) N.	Dorsiflexion
Lateral	Peroneus (Fibularis) Longus & Brevis	Superficial Peroneal (Fibular) N.	Eversion

⭐ Injury to the common peroneal nerve, often at the fibular neck, causes foot drop (inability to dorsiflex), resulting in a high-stepping gait.

Posterior Leg - Pushing the Pedal

Muscles of the posterior compartment of the leg

Compartment	Muscles	Innervation	Main Action(s)
Superficial	Gastrocnemius, Soleus, Plantaris	Tibial Nerve	Plantarflexion
Deep	Tibialis Posterior, FHL, FDL	Tibial Nerve	Plantarflexion, Inversion

⭐ The Achilles tendon (calcaneal tendon), formed by the gastrocnemius and soleus, is the strongest tendon in the body. Rupture causes sudden pain and inability to plantarflex.

Clinical Integration - Walking the Walk

The gait cycle integrates all lower limb muscle actions for efficient walking. It's divided into two main phases: the Stance Phase, where the foot is on the ground (60%), and the Swing Phase, where it's in the air (40%). Each sub-phase requires precise muscle activation.

⭐ A 'gluteus medius lurch' during the stance phase is a classic sign of a weak gluteus medius on the supported side, compensating for a Trendelenburg gait.

High-Yield Points - ⚡ Biggest Takeaways

Femoral nerve (L2-L4) injury impairs hip flexion and knee extension.

Obturator nerve (L2-L4) damage weakens thigh adduction.

Superior gluteal nerve lesion causes a Trendelenburg gait due to weak hip abductors.

Inferior gluteal nerve injury weakens hip extension (gluteus maximus), making climbing stairs difficult.

Common peroneal nerve injury results in foot drop (loss of dorsiflexion and eversion).

Tibial nerve damage impairs plantarflexion and inversion of the foot.

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