Skeletal Anatomy, Human Anatomy, USMLE Step 1 - Full Vignette with Extended Explanations

Описание: A 25-year-old scaffolding worker experiences a sudden twist of her right knee after misstepping at work, followed by outer knee pain, foot slapping during ambulation, and sensory changes over the dorsum of the foot. On exam, focal tenderness, weakness in foot movements, and altered sensation are present. What neurologic and anatomic factors should be considered in assessing risks associated with this knee injury?

VIDEO INFO
Category: Skeletal Anatomy, Human Anatomy, USMLE Step 1
Difficulty: Moderate - Intermediate level - Requires solid foundational knowledge
Question Type: Complications
Case Type: Tricky Findings

Explore more ways to learn on this and other topics by going to https://endlessmedical.academy/auth?h...

QUESTION
A 25-year-old woman who works as a scaffolding installer missteps while descending a low platform at a job site and twists her right knee and lower leg into a brief varus position before catching herself on a rail. She does not fall to the ground and denies head trauma or loss of consciousness....

OPTIONS
A. Foot drop from common fibular (peroneal) nerve injury at the fibular neck, with weakness of ankle dorsiflexion and foot eversion and sensory loss over the dorsum of the foot including the first web space.
B. Isolated deep fibular (peroneal) nerve palsy causing loss of great toe and ankle dorsiflexion with numbness confined to the first dorsal web space, while foot eversion remains preserved.
C. Tibial nerve neuropathy at the tarsal tunnel producing weakness of plantarflexion and inversion with numbness limited to the plantar surface of the foot.
D. Saphenous nerve injury resulting in medial leg cutaneous numbness only, without foot dorsiflexion weakness or gait disturbance.

CORRECT ANSWER
A. Foot drop from common fibular (peroneal) nerve injury at the fibular neck, with weakness of ankle dorsiflexion and foot eversion and sensory loss over the dorsum of the foot including the first web space.

EXPLANATION
"Foot drop from common fibular (peroneal) nerve injury at the fibular neck, with weakness of ankle dorsiflexion and foot eversion and sensory loss over the dorsum of the foot including the first web space." The common fibular nerve wraps superficially around the fibular neck before dividing into the deep and superficial fibular branches; it is highly exposed to stretch or compression when this region is injured. The patient s mechanism (varus twist) and imaging (fibular neck fracture) match the anatomic danger zone. On examination, ankle dorsiflexion and great toe extension weakness indicate deep branch involvement, while eversion weakness and dorsal foot sensory loss implicate the superficial branch. Numbness in the first dorsal web space is a key localizing sign because it is supplied by the deep fibular nerve.

"Isolated deep fibular (peroneal) nerve palsy causing loss of great toe and ankle dorsiflexion with numbness confined to the first dorsal web space, while foot eversion remains preserved." is close but incomplete because eversion weakness is present here, indicating a lesion proximal to the bifurcation. "Tibial nerve neuropathy at the tarsal tunnel producing weakness of plantarflexion and inversion with numbness limited to the plantar surface of the foot." does not fit the motor pattern or sensory territory....


Further reading:

Links to sources are provided for optional further reading only. The questions and explanations are independently authored and do not reproduce or adapt any specific third-party text or content.

---------------------------------------------------

Our cases and questions come from the https://EndlessMedical.Academy quiz engine - multi-model platform. Each question and explanation is forged by consensus between multiple top AI models (i.e. Open AI GPT, Claude, Grok, etc.), with automated web searches for the latest research and verified references. Calculations (e.g. eGFR, dosages) are checked via code execution to eliminate errors, and all references are reviewed by several AIs to minimize hallucinations.

Important note: This material is entirely AI-generated and has not been verified by human experts; despite stringent consensus checks, perfect accuracy cannot be guaranteed. Exercise caution - always corroborate the content with trusted references or qualified professionals, and never apply information from this content to patient care or clinical decisions without independent verification.

Clinicians already rely on AI and online tools - myself included - so treat this content as an additional focused aid, not a replacement for proper medical education. Visit https://endlessmedical.academy for more AI-supported resources and cases.

This material can not be treated as medical advice. May contain errors.

---------------------------------------------------