MD Musculoskeletal and Connective Tissue 3 — Questions and Answers
Question 1: A 25-year-old man sustains a knee injury while playing soccer. He reports hearing a 'pop' and has a positive anterior drawer test. Which structure is most likely injured?
- Anterior cruciate ligament (Correct answer)
- Posterior cruciate ligament
- Medial collateral ligament
- Lateral meniscus
Correct answer: Anterior cruciate ligament
A positive anterior drawer test (anterior tibial translation on the femur) indicates anterior cruciate ligament (ACL) tear.
Question 2: A 65-year-old woman presents with bilateral hip pain that worsens with activity and is relieved by rest. X-ray shows joint space narrowing, subchondral sclerosis, and osteophytes. What is the underlying pathology?
- Progressive loss of articular cartilage with subchondral bone remodeling (Correct answer)
- Synovial proliferation with pannus formation
- Urate crystal deposition in periarticular tissues
- Immune complex deposition in the synovium
Correct answer: Progressive loss of articular cartilage with subchondral bone remodeling
Osteoarthritis is characterized by progressive articular cartilage degradation leading to subchondral sclerosis, cyst formation, and osteophyte development.
Question 3: A 50-year-old woman with rheumatoid arthritis develops atlantoaxial instability. Which cervical vertebrae are involved, and what is the primary danger?
- C1-C2 instability with risk of spinal cord compression (Correct answer)
- C5-C6 instability with nerve root compression
- C2-C3 instability with vertebral artery injury
- C3-C4 instability with diaphragm paralysis
Correct answer: C1-C2 instability with risk of spinal cord compression
RA-related erosion of the transverse ligament causes C1-C2 (atlantoaxial) instability, risking odontoid process compression of the spinal cord.
Question 4: A 30-year-old man develops urethritis, conjunctivitis, and asymmetric arthritis after a Chlamydia trachomatis infection. Which HLA type is associated with increased risk?
- HLA-B27 (Correct answer)
- HLA-DR4
- HLA-DR3
- HLA-B51
Correct answer: HLA-B27
Reactive arthritis (formerly Reiter syndrome) is strongly associated with HLA-B27 and occurs after genitourinary or gastrointestinal infections.
Question 5: A 55-year-old man with gout has recurrent attacks despite dietary modification. Serum uric acid is 9.8 mg/dL. Which enzyme deficiency would cause this hyperuricemia through overproduction rather than underexcretion?
- Hypoxanthine-guanine phosphoribosyltransferase (HGPRT) deficiency (Correct answer)
- Adenosine deaminase deficiency
- Purine nucleoside phosphorylase deficiency
- Glucose-6-phosphatase deficiency
Correct answer: Hypoxanthine-guanine phosphoribosyltransferase (HGPRT) deficiency
HGPRT deficiency (Lesch-Nyhan syndrome partial form) leads to decreased purine salvage and excess de novo purine synthesis, causing uric acid overproduction.
Question 6: A 72-year-old woman presents with acute knee pain and swelling. Synovial fluid shows positively birefringent rhomboid-shaped crystals under polarized light. What is the diagnosis?
- Pseudogout (calcium pyrophosphate deposition disease) (Correct answer)
- Gout
- Septic arthritis
- Hemarthrosis
Correct answer: Pseudogout (calcium pyrophosphate deposition disease)
Calcium pyrophosphate dihydrate (CPPD) crystals are positively birefringent and rhomboid-shaped, distinguishing pseudogout from gout's negatively birefringent needle-shaped urate crystals.
Question 7: A 45-year-old man with psoriasis develops DIP joint involvement, nail pitting, and 'sausage digits.' Rheumatoid factor is negative. What pattern of psoriatic arthritis does he have?
- Distal interphalangeal joint predominant disease (Correct answer)
- Symmetric polyarthritis
- Arthritis mutilans
- Axial spondyloarthropathy
Correct answer: Distal interphalangeal joint predominant disease
DIP joint involvement with nail changes and dactylitis (sausage digits) is the classic distal pattern of psoriatic arthritis, which is seronegative.
MD Musculoskeletal and Connective Tissue 3
A 25-year-old man sustains a knee injury while playing soccer.
He reports hearing a 'pop' and has a positive anterior drawer test.
Which structure is most likely injured?