An adolescent has vague knee pain. With the knee fully flexed, there is a discrete tender area on the lateral portion of the articular cartilage of the medial femoral condyle. Which is the most likely diagnosis?

Correct Answer: D

Rationale: Osteochondritis dissecans involves cartilage defects, often causing localized tenderness in the femoral condyle.

Correct Answer: B

Rationale: Heart failure leads to increased intravascular pressure and volume due to impaired pumping, causing fluid to leak into interstitial spaces, resulting in edema.

Correct Answer: C

Rationale: Gastroenteritis is the most common cause of hypokalemia in children due to potassium loss via diarrhea.

Correct Answer: D

Rationale: Aluminum binders are avoided in chronic renal insufficiency due to toxicity; others are standard treatments.

Correct Answer: D

Rationale: Hypotension can impair ventilation, causing CO₂ retention and respiratory acidosis.