Chronic pain is diagnosed through a combination of your medical history, physical examination, standardized questionnaires, and sometimes lab tests or imaging. There is no single test that confirms chronic pain. Instead, clinicians piece together information from multiple sources to understand what type of pain you have, how severe it is, and what might be driving it. The key threshold: pain that persists or recurs for longer than three months is classified as chronic.
The Pain History Interview
The diagnostic process starts with a detailed conversation. Your doctor will walk through a structured set of questions covering the character of your pain (burning, sharp, aching), when it started, where exactly you feel it, how long episodes last, what makes it worse, what makes it better, whether it radiates to other areas, and how severe it is on a 0 to 10 scale. The way you describe your pain matters more than you might expect. Burning or electric sensations point toward nerve involvement, while a deep ache that worsens with movement suggests musculoskeletal causes.
You’ll also be asked how pain affects your daily life: whether it disrupts sleep, limits your ability to work, or has changed your mood. These details help determine not just the type of pain but its functional impact, which directly shapes treatment decisions.
How Chronic Pain Is Classified
The International Association for the Study of Pain developed a classification system now used in the ICD-11, the global standard for medical diagnoses. It divides chronic pain into seven categories: chronic primary pain (where pain itself is the condition, not a symptom of something else), chronic cancer pain, chronic post-traumatic and postsurgical pain, chronic neuropathic pain, chronic headache and orofacial pain, chronic visceral pain (from internal organs), and chronic musculoskeletal pain.
The distinction between primary and secondary chronic pain is important. In chronic primary pain, there may be no identifiable tissue damage or disease explaining the pain. In secondary chronic pain, the pain stems from an underlying condition like arthritis, nerve damage, or cancer. Your doctor’s goal during diagnosis is to figure out which category fits, because each one calls for different management.
Standardized Pain Scales
Doctors use validated questionnaires to measure pain severity and its effect on your life in a consistent, trackable way. One widely used tool is the Graded Chronic Pain Scale (revised), which sorts people into four grades. Grade 0 means chronic pain is absent, meaning you don’t have pain on most days or every day. Grade 1 is mild chronic pain. Grade 2 is bothersome chronic pain. Grade 3 is high-impact chronic pain, defined as pain that limits your life activities or work on most days.
A simpler screening tool called the PEG scale asks just three questions, rating your pain intensity, how much pain interferes with enjoyment of life, and how much it interferes with general activity, each on a 0 to 10 scale. A combined score of 12 or higher (averaging 4 or more per question) indicates moderate to severe, bothersome pain. These scores give your doctor a baseline to compare against over time and help determine whether treatment is working.
The Physical Examination
A chronic pain physical exam is more involved than a standard checkup. Your doctor will observe how you move before any hands-on testing, watching how you transition from sitting to standing, how you walk, and whether you favor one side. These observations reveal a lot about where pain originates and how much it limits function.
From there, the exam becomes targeted based on your pain location. For back pain, you might be asked to perform a straight leg raise while seated (lifting one leg with the knee straight) or a slump test, both of which stretch the sciatic nerve and can reproduce pain caused by nerve compression. Heel walking tests ankle strength controlled by the L4 nerve root, while difficulty with toe walking or single-leg heel raises points to S1 or S2 nerve involvement.
For neck and shoulder pain, your doctor will check range of motion by having you turn your head side to side, tilt ear to shoulder, and flex and extend. They’ll press on the muscles along your spine and at the base of your skull to check for tenderness or spasm. Shoulder-specific tests might involve lifting a weighted object with your arm outstretched (to check for rotator cuff problems) or crossing your ankle over the opposite knee while pulling the knee toward your chest (to evaluate hip and sacroiliac joint pain).
The exam also includes checking for muscle wasting or visible asymmetry, which can signal nerve damage that has been present long enough to weaken the muscles a nerve supplies.
Screening for Psychological Factors
Chronic pain and mental health are deeply connected, and a thorough evaluation includes screening for psychological factors that influence pain and recovery. Clinicians look for what are known as “yellow flags,” psychosocial risk factors that can become obstacles to getting better. Fear of movement or injury is the most common, reported by nearly 88% of patients with chronic low back pain in one study. Other yellow flags include catastrophizing (expecting the worst outcome), depression, anxiety, and workplace or financial stress.
Short screening tools like the PHQ-4 assess depression and anxiety symptoms with just four questions, rating how often you’ve experienced core symptoms over the past two weeks. A score of 6 or higher suggests moderate to severe psychological distress. This isn’t about questioning whether your pain is “real.” It’s about recognizing that fear, mood, and stress physically amplify pain signals and can keep you stuck in a cycle that’s harder to break without addressing all the contributing factors.
Blood Tests and Inflammatory Markers
Blood work helps rule in or rule out inflammatory and autoimmune conditions that cause chronic pain. The two most common tests are C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), both of which measure inflammation in the body. In healthy people, CRP levels sit at 0.8 to 1.0 mg/dL or lower. Elevated levels tell your doctor inflammation is present somewhere, but not where or why, so these results are always interpreted alongside your symptoms and other findings.
Depending on your pain pattern, your doctor may also order tests for rheumatoid factor, antinuclear antibodies (to screen for autoimmune conditions), uric acid (for gout), vitamin D levels, or thyroid function. None of these tests diagnose chronic pain on their own, but they can identify treatable underlying causes.
Nerve Testing
When nerve damage is suspected, nerve conduction studies and electromyography (EMG) can objectively measure how well your nerves are functioning. Nerve conduction studies send small electrical impulses along a nerve and measure how fast the signal travels. Slowed conduction speed or delayed response times confirm that a nerve is damaged or compressed. EMG involves inserting a thin needle into muscles to record their electrical activity, which reveals whether nerve signals are reaching the muscles properly.
A more specialized tool called quantitative sensory testing (QST) measures how your nervous system processes different sensations. During QST, a clinician applies controlled heat, cold, pressure, and mechanical stimuli to your skin and records the point at which you feel them and the point at which they become painful. This can reveal two important patterns. Peripheral sensitization shows up as lowered pain thresholds, meaning you feel pain from stimuli that shouldn’t hurt. Central sensitization, where the spinal cord and brain have become hypersensitive, is identified through temporal summation, where repeated tapping or thermal pulses produce escalating pain rather than a steady sensation. QST has been used to detect these changes in conditions ranging from chronic low back pain to knee osteoarthritis.
When Imaging Helps and When It Doesn’t
Many people expect an MRI or X-ray to reveal the source of their chronic pain, but imaging is useful in only a narrow set of circumstances. For low back pain, the most common chronic pain condition, only 5 to 10% of cases involve a specific underlying spinal pathology like cancer, infection, inflammatory disease, fracture, or severe nerve damage. The remaining 90 to 95% is classified as nonspecific, meaning imaging won’t identify a clear structural cause or change how the pain is managed.
The Canadian Spine Society’s guidance is straightforward: don’t routinely image patients with low back pain regardless of how long they’ve had it, unless there are clinical red flags suggesting something serious, or imaging is needed to plan a specific procedure. Unnecessary imaging can actually cause harm. Incidental findings, things that show up on a scan but aren’t causing your symptoms, can lead to anxiety, additional testing, or even unneeded procedures. CT scans and X-rays also expose you to radiation. When red flags are present, however, MRI is the preferred tool because it shows soft tissue detail including discs, nerves, and spinal cord without radiation.
This doesn’t mean your pain isn’t real if imaging looks normal. It means that in most chronic pain cases, the problem lies in how the nervous system is processing pain signals rather than in visible structural damage, which is exactly what tools like QST and the clinical exam are designed to detect.