1. General Principles & Basic Science MCQs

A 65-year-old woman with metastatic breast cancer is treated with an agent to prevent skeletal-related events. The agent is a monoclonal antibody that targets RANKL. Which of the following is the primary cellular effect of this medication?

An infant presents with multiple fractures, cranial nerve palsies, and diffuse osteosclerosis on radiographs. A diagnosis of malignant infantile osteopetrosis is made. The most common genetic mutation associated with this condition affects which of the following osteoclast functions?

A 6-year-old boy presents with refusal to walk, gingival bleeding, and petechiae. Radiographs of the lower extremities show osteopenia, a dense zone of provisional calcification, and an adjacent radiolucent band. The underlying nutritional deficiency impairs which of the following steps in collagen synthesis?

In normal articular cartilage, which of the following zones contains the highest concentration of water and has collagen fibers oriented parallel to the joint surface?

Continuous administration of Parathyroid Hormone (PTH), as seen in primary hyperparathyroidism, leads to net bone resorption. Which of the following best describes the direct action of PTH on bone cells to induce this effect?

A diaphyseal fracture is treated with rigid plate fixation and absolute stability, achieving a gap of less than 0.1 mm. Which of the following best describes the mechanism of bone healing expected in this scenario?

In orthopedic implant metallurgy, mixing components made of 316L stainless steel and titanium alloys is generally avoided. Which of the following best explains the risk of combining these two different metals in vivo?

A 2-year-old child presents with bowing of the legs, alopecia, and hypocalcemia. Laboratory tests show elevated levels of 1,25-dihydroxyvitamin D and elevated parathyroid hormone. Which of the following is the most likely underlying defect?

A patient presents with acute monoarticular knee swelling. A joint aspiration is performed. The synovial fluid has a leukocyte count of 75,000 cells/mm^3 with 90% polymorphonuclear cells. Which of the following is the most appropriate next step in management?

Which of the following enzymes is considered a primary driver of articular cartilage matrix degradation in the pathogenesis of osteoarthritis?

In the medical management of an unresectable or recurrent giant cell tumor of bone, denosumab is frequently utilized. Which of the following best describes its primary mechanism of action?

A 4-year-old child presents with multiple fractures and is found to have diffuse osteosclerosis and 'bone-in-bone' appearance on radiographs. Genetic testing reveals a mutation in the carbonic anhydrase II gene. This condition is primarily caused by a defect in which cellular process?

A 6-year-old boy presents with progressive bowing of his lower extremities. Laboratory evaluation demonstrates a normal serum calcium, extremely low phosphorus, and elevated alkaline phosphatase. Which of the following is the most likely diagnosis?

During the early stages of primary osteoarthritis, which of the following biochemical changes initially occurs in the articular cartilage matrix?

A patient with severe dietary restrictions presents with bleeding gums, petechiae, and joint pain. Radiographs show osteopenia and a dense provisional zone of calcification. The underlying cellular defect involves failure of which step in collagen synthesis?

Parathyroid hormone (PTH) regulates serum calcium levels by eventually stimulating bone resorption. Which of the following cells does PTH directly bind to in order to initiate this resorptive cascade?

In the pathogenesis of rheumatoid arthritis, joint destruction is primarily mediated by the hyperplastic synovium (pannus). Which of the following cells within the pannus is the major source of the destructive matrix metalloproteinases?

Romosozumab, an agent used for the treatment of severe osteoporosis, exerts its anabolic effect on bone by directly binding and inhibiting which of the following molecules?

A 65-year-old man presents with progressive bowing of his tibiae and an increasing hat size. Laboratory tests show markedly elevated serum alkaline phosphatase with normal calcium and phosphorus. A bone biopsy would most likely demonstrate which microscopic finding?

During the incorporation of a cortical structural allograft, the process by which host osteoclasts resorb the graft and osteoblasts lay down new bone in its place is known as: