A 60-year-old man seeks evaluation at a medical office due to leg pain while walking. He says the pain starts in his buttocks and extends to his thighs and down to his calves. Previously, the pain resolved with rest, but the pain now persists in his feet, even during rest. His past medical history is significant for diabetes mellitus, hypertension, and cigarette smoking. The vital signs are within normal limits. The physical examination shows an atrophied leg with bilateral loss of hair. Which of the following is the most likely cause of this patient’s condition?

Narrowing and calcification of vessels

Decreased permeability of endothelium

A 38-year-old man is brought to the emergency department after suffering a motor vehicle accident as the passenger. He had no obvious injuries, but he complains of excruciating right hip pain. His right leg is externally rotated, abducted, and extended at the hip and the femoral head can be palpated anterior to the pelvis. Plain radiographs of the pelvis reveal a right anterior hip dislocation and femoral head fracture. Which sensory and motor deficits are most likely in this patient's right lower extremity?

Numbness of the medial side of the thigh and inability to adduct the thigh

Loss of sensation laterally below the knee, weak thigh extension and knee flexion

Numbness of the ipsilateral scrotum and upper medial thigh

Sensory loss to the dorsal surface of the foot and part of the anterior lower and lateral leg and foot drop

Paresis and numbness of the medial thigh and medial side of the calf, weak hip flexion and knee extension

A 56-year-old man presents to the emergency room after being in a motor vehicle accident. He was driving on an icy road when his car swerved off the road and ran head on into a tree. He complains of severe pain in his right lower extremity. He denies loss of consciousness during the accident. His past medical history is notable for poorly controlled hypertension, hyperlipidemia, and major depressive disorder. He takes enalapril, atorvastatin, and sertraline. His temperature is 99.1°F (37.3°C), blood pressure is 155/85 mmHg, pulse is 110/min, and respirations are 20/min. On exam, he is alert and fully oriented. He is unable to move his right leg due to pain. Sensation is intact to light touch in the sural, saphenous, tibial, deep peroneal, and superficial peroneal distributions. His leg appears adducted, flexed, and internally rotated. An anteroposterior radiograph of his pelvis would most likely demonstrate which of the following findings?

Femoral head smaller than contralateral side and posterior to acetabulum

Fracture line extending between the greater and lesser trochanters

Femoral head larger than contralateral side and inferior to acetabulum

Fracture line extending through the femoral neck

Fracture line extending through the subtrochanteric region of the femur

A 45-year-old male presents to his primary care provider with an abnormal gait. He was hospitalized one week prior for acute cholecystitis and underwent a laparoscopic cholecystectomy. He received post-operative antibiotics via intramuscular injection. He recovered well and he was discharged on post-operative day #3. However, since he started walking after the operation, he noticed a limp that has not improved. On exam, his left hip drops every time he raises his left foot to take a step. In which of the following locations did this patient likely receive the intramuscular injection?

Superomedial quadrant of the buttock

Superolateral quadrant of the buttock

Inferomedial quadrant of the buttock

Inferolateral quadrant of the buttock

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

Clinical correlations of lower limb for USMLE Step 2 CK: High-Yield Anatomy Lessons

Nerve Injuries - Shocking Tales

Common Peroneal (Fibular) N. (L4-S2):
- Injury: Most common; fibular neck fracture, lateral compression.
- Motor: Foot drop (impaired dorsiflexion/eversion). Unopposed plantarflexion/inversion.
- Sensory: Anterolateral leg & dorsum of foot.
- 📌 PED: Peroneal Everts & Dorsiflexes.
Tibial N. (L4-S3):
- Injury: Popliteal fossa compression (Baker's cyst), tarsal tunnel syndrome.
- Motor: Can't stand on tiptoes (impaired plantarflexion/inversion).
- Sensory: Sole of the foot.
- 📌 TIP: Tibial Inverts & Plantarflexes.
Superior Gluteal N. (L4-S1):
- Injury: Iatrogenic (misplaced gluteal injection).
- Motor: Trendelenburg gait (pelvic drop on contralateral side).

⭐ Injury to the common peroneal nerve often presents as "foot drop." Patients may develop a high-stepping "steppage gait" to compensate and avoid tripping over their toes.

Normal vs. Trendelenburg Gait

Vascular Issues - Plumbing Problems

Peripheral Artery Disease (PAD):
- Atherosclerosis → intermittent claudication (cramping pain on exertion).
- Key diagnostic: Ankle-Brachial Index (ABI) < 0.9.
- Signs: cool, pale, hairless skin; non-healing ulcers.
Deep Vein Thrombosis (DVT):
- Clot in a deep vein, usually the calf.
- 📌 Virchow's Triad: Stasis, Hypercoagulability, Endothelial damage.
- Presents as unilateral leg swelling, warmth, and erythema.
Varicose Veins:
- Incompetent valves in superficial veins → dilated, tortuous vessels.

⭐ Proximal DVTs (popliteal, femoral, iliac) are far more likely to embolize to the lungs, causing a pulmonary embolism, than distal (calf) DVTs.

Ankle-Brachial Index (ABI) Measurement and Interpretation

MSK Injuries - Broken Beams

Femoral Neck Fracture: Presents with a shortened, externally rotated leg. High risk of avascular necrosis (AVN) due to tenuous blood supply.
Tibial Plateau Fracture: Often from a direct valgus force (e.g., car bumper). Complications include popliteal artery injury and common peroneal nerve damage (foot drop).
Ankle Fracture: Always examine the proximal fibula with medial malleolar injuries to rule out a Maisonneuve fracture, which indicates syndesmotic instability.
Stress Fracture: Common in athletes and military recruits. The 2nd metatarsal is the most frequent site.

⭐ The medial circumflex femoral artery is the primary blood supply to the femoral head. Intracapsular femoral neck fractures disrupt this artery, leading to a high rate of avascular necrosis.

Blood supply to femoral head and neck

Gait Analysis - The Limp Bizkit

Antalgic Gait:
- Cause: Pain (e.g., trauma, osteoarthritis).
- Presentation: Shortened stance phase on the affected side to minimize weight-bearing.
Trendelenburg Gait:
- Cause: Weakness of hip abductors (gluteus medius/minimus), superior gluteal nerve injury.
- Presentation: Pelvis drops on the contralateral (unaffected) side during swing phase.
Steppage (Equine) Gait:
- Cause: Foot drop due to common peroneal nerve palsy or L5 radiculopathy.
- Presentation: Exaggerated hip/knee flexion to clear the foot; may hear a "foot slap."

⭐ Trendelenburg Sign: A positive sign (pelvic drop) on the right side indicates a lesion of the left superior gluteal nerve.

Trendelenburg vs. Normal Gait: Pelvic Stability

High‑Yield Points - ⚡ Biggest Takeaways

Femoral neck fractures risk avascular necrosis of the femoral head by disrupting the medial circumflex femoral artery.

Common fibular nerve injury at the fibular neck causes foot drop (impaired dorsiflexion and eversion).

ACL tears, common in athletes, result from pivoting and show a positive anterior drawer sign.

The "unhappy triad" is a combined injury of the ACL, MCL, and medial meniscus.

Achilles tendon rupture presents with a palpable gap and a positive Thompson test.

Deep vein thrombosis (DVT) is a major source of life-threatening pulmonary emboli.

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