Musculoskeletal Radiology
What the exam tests
MSK radiology covers fracture detection, arthritis patterns, bone tumors, infection, sports injuries, and spine imaging. Expect radiographic lines and angles, MRI signal patterns, and complication recognition.
Core rules
- In children, the anterior humeral line should intersect the middle third of the capitellum; displacement suggests supracondylar fracture.
- A posterior fat pad sign indicates an occult elbow effusion and possible fracture.
- Osteoarthritis: joint space narrowing, sclerosis, osteophytes, subchondral cysts. Rheumatoid arthritis: marginal erosions, uniform joint space loss, osteopenia.
- Bone marrow edema is bright on fluid-sensitive sequences and dark on T1.
Worked example
A 10-year-old falls and has elbow pain. The lateral radiograph shows a posterior fat pad and the anterior humeral line passes through the anterior third of the capitellum. Reasoning: these findings indicate a supracondylar fracture even if the fracture line is subtle. The child needs immobilization and orthopedic evaluation; neurovascular status must be documented because of risk to the brachial artery and median nerve.
Traps
Missing a non-displaced supracondylar fracture; confusing normal ossification centers with fracture fragments; and failing to check neurovascular status.
Key points
- Posterior fat pad sign suggests occult elbow fracture.
- Anterior humeral line should intersect the middle third of the capitellum.
- OA is characterized by narrowing, sclerosis, and osteophytes.
- RA causes marginal erosions and uniform joint space loss.
- Marrow edema is bright on STIR/T2 fat sat.