Musculoskeletal Examination, Evaluation, and Diagnosis
What the candidate must know
This domain rewards a hypothesis-driven exam. Start with the patient's irritability, symptom behavior (mechanical vs. chemical), and 24-hour pattern, then choose special tests based on the differential rather than running a fixed battery. Know the operating characteristics of the tests you cite: the validity of a single special test is usually modest, so clusters (e.g., Laslett's SIJ cluster, Ottawa rules, clinical prediction rules for lumbar manipulation) outperform isolated tests. Understand capsular patterns, end-feel terminology (capsular, empty, springy, hard), and how to distinguish referred somatic pain from radicular pain.
Traps
- Treating a positive test as a diagnosis. Ask: does this test change my probability enough to change management?
- Confusing sensitivity and specificity. A highly sensitive test is good for ruling out; a highly specific test is good for ruling in.
- Forgetting that red-flag screening precedes any special test. Unexplained weight loss, night pain unrelieved by position change, fever, and neurological progression change the plan.
- Mixing up dermatomal and peripheral nerve patterns (e.g., C6 vs. median nerve).
Rule of thumb
Use the SnNout/SpPin mnemonic: a highly Sensitive test that is Negative rules out (SnNout); a highly Specific test that is Positive rules in (SpPin).
Worked example
A patient has buttock pain, a negative straight-leg raise, and three of five positive SIJ provocation tests. Because the SIJ cluster is specific, a positive cluster meaningfully raises the probability of SIJ dysfunction; a single positive test would not.