How Do Clinicians Identify the Source of Pain?

Why Pain Source Is Not Always Obvious

Musculoskeletal diagnosis would be straightforward if pain always arose from the structure at the site of its experience. In practice, referred pain from deep somatic structures, radicular pain from nerve root irritation, the widespread sensitisation of central sensitisation, and the biomechanical chain reactions that produce secondary pain sites distant from the primary lesion all ensure that the correct source of pain is often not the most obvious one. A clinician who accepts the patient's description of pain location as a reliable guide to anatomical pathology will be wrong a substantial proportion of the time.

Systematic clinical assessment — moving from the broad to the specific, testing hypotheses rather than accepting initial impressions, and maintaining a consistent awareness of the multiple potential sources for any given pain presentation — is what distinguishes expert clinical reasoning from pattern-matching on symptoms alone.

The Subjective Assessment

The clinical assessment begins with a structured subjective assessment — a systematic history that gathers information along several key dimensions. Location and distribution: where is the pain, and how does it distribute? Does it radiate, refer, or remain localised? Quality: is the pain sharp, aching, burning, stabbing, deep, or superficial? Each quality carries diagnostic significance — burning suggests neural involvement; a deep, diffuse ache is characteristic of referred somatic pain; sharp and localised pain often indicates superficial structures. Behaviour: what aggravates it, what eases it, how does it behave through the day, and is it worse at rest or with activity? Onset and history: was there a precipitating event, or did it develop insidiously? What is the timeline, and what has been tried previously? Associated symptoms: are there neurological symptoms, systemic features, or other complaints that suggest a non-musculoskeletal source?

The subjective assessment alone — conducted by a skilled clinician — can generate a short-list of the most likely anatomical sources and the most appropriate subsequent tests to differentiate between them. It also serves the critical screening function of identifying red flag features that require medical referral before musculoskeletal treatment is commenced.

Observation and Postural Analysis

Before any active testing, clinical observation provides valuable structural information. Antalgic posture — the characteristic posture of protection adopted by the body around a painful structure — reveals which structures the nervous system is offloading and in which positions the pain is minimised. Forward head posture, protective lateral shift of the lumbar spine (an acute disc sign), guarded shoulder position, and unequal weight-bearing all reflect the pain-driven motor reorganisation that guides assessment. Muscle atrophy, asymmetry, and swelling are visible indicators of structural pathology or disuse. Gait abnormalities and movement quality during functional tasks provide dynamic information about which structures are being protected and how movement has been reorganised around the pain.

Movement and Functional Testing

Active and passive range of motion testing systematically explores the mechanical behaviour of the affected region. The pattern of movement restriction — which movements are limited, whether limitation is pain-limited or mechanically limited (end-feel), and whether limiting pain is reproduced or merely provoked — provides specific diagnostic information. Cyriax's concept of the capsular pattern describes the characteristic pattern of multi-directional restriction that indicates involvement of the entire joint capsule (as in adhesive capsulitis). A non-capsular pattern suggests involvement of specific structures rather than the whole capsule. Overpressure at the end of available range challenges passive structures that are not reached by active movement alone.

Palpation and Manual Testing

Systematic palpation of the relevant anatomical structures — bony landmarks, joint lines, muscle bellies, tendinous insertions, and neural structures — identifies localised tenderness, tissue thickening, temperature changes, and trigger point activity. Palpation findings must be interpreted in clinical context: tenderness alone is not a diagnosis; its location, quality, and relationship to the patient's presenting complaint determines its significance. Accessory joint mobility testing — applying controlled passive pressure in specific directions at each joint — assesses segmental mobility and identifies hypomobile or hypermobile segments, guiding manual therapy intervention.

Special Tests and Provocative Assessment

Orthopaedic special tests — standardised provocative manoeuvres designed to selectively stress specific anatomical structures — provide the most specific diagnostic information in the musculoskeletal assessment. Their diagnostic utility is characterised by their sensitivity (ability to identify true positives) and specificity (ability to exclude true negatives), which vary considerably across tests. The Hawkins-Kennedy test for shoulder impingement, the Thessaly test for meniscal pathology, the FADIR test for hip labral or femoroacetabular impingement, the slump test for sciatic nerve mechanosensitivity, and the straight leg raise for L4–S1 radiculopathy are among the tests with the most robust diagnostic utility in their respective domains.

Importantly, special tests should reproduce the patient's familiar pain — not just any pain — to be diagnostically significant. A positive test that provokes unfamiliar pain is less meaningful than a negative test that fails to provoke familiar pain in the expected distribution. The integration of multiple test results — rather than the result of any single test — is what drives diagnostic confidence.

Clinical Reasoning — Putting It Together

The conclusion of the assessment is a working diagnosis — the clinician's best current hypothesis about the anatomical source(s) of the pain and the biopsychosocial factors maintaining it. This diagnosis informs a targeted treatment plan and defines the specific outcomes that will constitute treatment success. It is held as a hypothesis to be tested through treatment response rather than a fixed conclusion, and it is updated with each reassessment as new information becomes available. This iterative, hypothesis-testing approach to clinical reasoning — rather than pattern-matching from surface symptoms to a predetermined diagnosis — is what characterises skilled musculoskeletal practice and produces the most accurate diagnoses and the most effective treatment outcomes.