Pain history, physical examination and red flags

A focused history and examination localize most pain generators. Know which findings rule in versus rule out, which red flags actually change probability, and the pattern features that separate common mimics.

1. Few red flags are truly informative. In a systematic review, most guideline-endorsed red flags barely changed probability; a history of malignancy was the most useful flag for spinal cancer, with a post-test probability of about 33% in the emergency-setting study (7% in primary care) ¹.
2. Straight leg raise tests work in opposite directions. The ipsilateral test is sensitive (0.92) with low specificity (0.28), so a negative result helps rule out herniation; the crossed test is specific (0.90) but insensitive (0.28), so a positive result helps rule it in ².
3. Ask about inflammatory back pain features. Improvement with exercise, night pain, insidious onset, onset before 40 and no improvement with rest; four of five favor inflammatory back pain ³.
4. Hip pain: groin versus lateral. Hip osteoarthritis classification centers on hip pain with painful or limited internal rotation ⁴. Lateral pain with focal trochanteric tenderness, worse side-lying and with resisted abduction, points to gluteal tendinopathy ⁵.
5. Recognize myofascial trigger points. A hyperirritable spot in a taut band that reproduces the patient's local and referred pain on pressure, sometimes with a local twitch response when needled, defines a trigger point ⁶.
6. Screen neurologic emergencies. Saddle anesthesia, urinary retention and reduced anal tone with bilateral leg symptoms indicate cauda equina syndrome and need emergent MRI ⁷.

A normal examination does not neutralize a prior cancer history in a patient with new back pain; that single flag justifies further evaluation ¹.

• Improvement with exercise is the strongest single inflammatory back pain feature (odds ratio 23.1) ³.
• A negative crossed straight leg raise does not exclude disc herniation ².
• Hip osteoarthritis criteria include internal rotation of 15 degrees or more that is painful, stiffness of 60 minutes or less and age over 50 ⁴.
• Trochanteric pain is reproduced by palpation and resisted abduction, unlike hip osteoarthritis ⁵.
• Many guideline red flags have untested or negligible diagnostic value ¹.
• Myofascial pain is regional, unlike the widespread pain of fibromyalgia ⁶.
• Most straight leg raise data come from surgical populations, and single tests perform poorly in isolation; combined findings perform better ².
• Urinary retention in suspected cauda equina syndrome marks a worse prognostic stage ⁷.

• Treating every listed red flag as equally predictive ¹.
• Reading a negative crossed straight leg raise as excluding herniation ².
• Calling lateral hip pain with trochanteric tenderness "hip arthritis" ⁵.
• Reassuring a patient with saddle anesthesia and urinary retention and arranging routine outpatient imaging ⁷.