A 19-year-old collegiate football player sustains an injury to his left knee during a game. He was running with the ball when he dodged a defensive player and fell, twisting his left knee. He felt a “pop” as he fell. When he attempts to bear weight on his left knee, it feels unstable, and "gives way." He needs assistance to walk off the field. The pain is localized diffusely over the knee and is non-radiating. His past medical history is notable for asthma. He uses an albuterol inhaler as needed. He does not smoke or drink alcohol. On exam, he has a notable suprapatellar effusion. Range of motion is limited in the extremes of flexion. When the proximal tibia is pulled anteriorly while the knee is flexed and the patient is supine, there is 1.5 centimeter of anterior translation. The contralateral knee translates 0.5 centimeters with a similar force. The injured structure in this patient originates on which of the following bony landmarks?

Posteromedial aspect of the lateral femoral condyle

Lateral aspect of the lateral femoral condyle

Lateral aspect of the medial femoral condyle

Medial aspect of the medial femoral condyle

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 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 35-year-old man comes to the physician because of a 3-month history of intermittent right lateral hip pain that radiates to the thigh. Climbing stairs and lying on his right side aggravates the pain. Examination shows tenderness to palpation over the upper lateral part of the right thigh. There is no swelling. When the patient is asked to abduct the right leg against resistance, tenderness is noted. An x-ray of the pelvis shows no abnormalities. Which of the following structures is the most likely source of this patient's pain?

Lateral femoral cutaneous nerve

Lower limb surface landmarks for USMLE Step 3: High-Yield Anatomy Lessons

Femoral Triangle & Thigh - Gateway to the Leg

Femoral Triangle Anatomy: Nerves, Vessels, and Sheath

Borders (SAIL): Superiorly by the inguinal ligament, Laterally by the Sartorius, and Medially by the Adductor longus.
Floor: Iliopsoas and pectineus muscles.
Roof: Fascia lata.
Contents (NAVEL): From lateral to medial:
- Femoral Nerve
- Femoral Artery
- Femoral Vein
- Empty space (Femoral canal)
- Lymphatics

⭐ Femoral Hernias: Protrude through the femoral ring and canal, medial to the femoral vein. They are more common in females and have a high risk of strangulation.

Gluteal Region - Powerhouse Posterior

Gluteal region surface landmarks and safe injection site

Bony Palpation Points:
- Iliac Crest: Superior border of the ilium; its highest point aligns with the L4 vertebra.
- Posterior Superior Iliac Spine (PSIS): Often visible as skin dimples; marks the level of the S2 vertebra and sacroiliac joint.
- Ischial Tuberosity: Weight-bearing point in sitting; sciatic nerve lies midway between here and the greater trochanter.
- Greater Trochanter: Prominent lateral projection of the femur.
Safe Intramuscular (IM) Injection Zone:
- Superolateral Quadrant: Avoids sciatic nerve and superior gluteal vessels.

⭐ Trendelenburg Sign: Injury to the superior gluteal nerve weakens the gluteus medius/minimus muscles. This results in the pelvis dropping on the opposite side of the body when that leg is lifted off the ground.

Knee & Popliteal Fossa - The Crucial Hinge

Popliteal fossa surface and deep anatomy

Anterior Landmarks:
- Patella: Sesamoid bone within quadriceps tendon.
- Tibial Tuberosity: Bony prominence inferior to the patella; attachment for patellar ligament (mediates L4 patellar reflex).
- Femoral & Tibial Condyles: Palpable on either side of the patella.
- Fibular Head: Palpable on the superolateral aspect of the leg.
Popliteal Fossa (Posterior):
- Diamond-shaped space behind the knee.
- 📌 Mnemonic for contents (Medial to Lateral): Serve And Volley Next Ball ( Semimembranosus/tendinosus, Artery, Vein, Nerve, Biceps femoris).

⭐ The common fibular (peroneal) nerve is highly vulnerable to injury as it wraps around the neck of the fibula, leading to foot drop.

Leg, Ankle & Foot - Ground Control

Lower limb surface landmarks and pulse points

Leg & Knee Proximities:
- Tibial tuberosity: Bony prominence below the patella; patellar ligament insertion.
- Head of fibula: Palpable on the superolateral leg; common fibular nerve courses around it.
- Anterior border of tibia (shin): Sharp, subcutaneous bone edge.
Ankle & Foot Landmarks:
- Malleoli: Medial (tibia) and lateral (fibula) form the key ankle stabilizers.
- Dorsalis pedis pulse: Found on dorsum of foot, just lateral to the extensor hallucis longus tendon.

⭐ To check for peripheral artery disease, palpate the dorsalis pedis pulse. Its absence can be a critical sign of vascular insufficiency.

📌 Mnemonic (Tarsal Tunnel): Tom, Dick, And Very Nervous Harry for contents behind medial malleolus.

High‑Yield Points - ⚡ Biggest Takeaways

The femoral triangle is the primary site for femoral artery access and femoral hernias.

Gluteal injections must be in the superolateral quadrant to avoid the sciatic nerve.

The great saphenous vein, anterior to the medial malleolus, is key for CABG.

Palpate the dorsalis pedis pulse lateral to the EHL tendon to assess foot circulation.

The common fibular nerve is vulnerable at the fibular neck, risking foot drop.

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