Back pain may be classified by various methods to aid its diagnosis and management. The duration of back pain is considered in three categories, following the expected pattern of healing of connective tissue. Acute pain lasts up to 12 weeks, subacute pain refers to the second half of the acute period (6 to 12 weeks), and chronic pain is pain which persists beyond 12 weeks.

Back pain is pain in any region of the back. It is divided into neck pain (cervical), middle back pain (thoracic), lower back pain (lumbar) or coccydynia (tailbone or sacral pain) based on the segment affected. The lumbar area is the most common area for pain, as it supports most of the weight in the upper body. Episodes of back pain may be acute, sub-acute, or chronic depending on the duration. The pain may be characterized as a dull ache, shooting or piercing pain, or a burning sensation. Discomfort can radiate into the arms and hands as well as the legs or feet, and may include numbness, or weakness in the legs and arms.

Back pain can originate from the muscles, nerves, bones, joints or other structures in the spine. Internal structures such as the gallbladder, pancreas, aorta, and kidneys may also cause referred pain in the back.

Back pain is common, with about nine out of ten adults experiencing it at some point in their life, and five out of ten working adults having it every year. Some estimate up to 95% of Americans will experience back pain at some point in their lifetime. It is the most common cause of chronic pain, and is a major contributor of missed work and disability. However, it is rare for back pain to be permanently disabling. In most cases of herniated disks and stenosis, rest, injections or surgery have similar general pain resolution outcomes on average after one year. In the United States, acute low back pain is the fifth most common reason for physician visits and causes 40% of missed days off work. Additionally, it is the single leading cause of disability worldwide.

In the common presentation of acute low back pain, pain develops after movements that involve lifting, twisting, or forward-bending. The symptoms may start soon after the movements or upon waking up the following morning. The description of the symptoms may range from tenderness at a particular point to diffuse pain. It may or may not worsen with certain movements, such as raising a leg, or positions, such as sitting or standing. Pain radiating down the legs (known as sciatica) may be present. The first experience of acute low back pain is typically between the ages of 20 and 40. This is often a person's first reason to see a medical professional as an adult. Recurrent episodes occur in more than half of people with the repeated episodes being generally more painful than the first.

Other problems may occur along with low back pain. Chronic low back pain is associated with sleep problems, including a greater amount of time needed to fall asleep, disturbances during sleep, a shorter duration of sleep, and less satisfaction with sleep. In addition, a majority of those with chronic low back pain show symptoms of depression or anxiety.

Radicular pain, or radiculitis, is pain "radiated" along the dermatome (sensory distribution) of a nerve due to inflammation or other irritation of the nerve root (radiculopathy) at its connection to the spinal column. A common form of radiculitis is sciatica – radicular pain that radiates along the sciatic nerve from the lower spine to the lower back, gluteal muscles, back of the upper thigh, calf, and foot as often secondary to nerve root irritation from a spinal disc herniation or from osteophytes in the lumbar region of the spine.

The thoracic spine begins at the base of the neck and extends to the middle of the trunk. Any pain in this area is considered "middle back pain".

The exact symptoms associated with middle back pain will depend upon the underlying cause. Most middle back pain is not serious in nature. However, it does tend to have more serious pathology associated with it than pain in the neck or low back. Symptoms can include pain, either locally near the spine or referred along area the corresponding nerve dermatome. Symptoms can also include numbness or pins and needles when nerve irritation or compression is involved. Weakness in the legs or loss of bowel or bladder control in the presence of thoracic spine pain can indicate spinal cord compression and should be investigated.

Breakthrough pain is transitory acute pain that comes on suddenly and is not alleviated by the patient's regular pain management. It is common in cancer patients who often have background pain that is generally well-controlled by medications, but who also sometimes experience bouts of severe pain that from time to time "breaks through" the medication. The characteristics of breakthrough cancer pain vary from person to person and according to the cause. Management of breakthrough pain can entail intensive use of opioids, including fentanyl.

Phantom pain is pain felt in a part of the body that has been amputated, or from which the brain no longer receives signals. It is a type of neuropathic pain.

The prevalence of phantom pain in upper limb amputees is nearly 82%, and in lower limb amputees is 54%. One study found that eight days after amputation, 72% of patients had phantom limb pain, and six months later, 67% reported it. Some amputees experience continuous pain that varies in intensity or quality; others experience several bouts of pain per day, or it may reoccur less often. It is often described as shooting, crushing, burning or cramping. If the pain is continuous for a long period, parts of the intact body may become sensitized, so that touching them evokes pain in the phantom limb. Phantom limb pain may accompany urination or defecation.

Local anesthetic injections into the nerves or sensitive areas of the stump may relieve pain for days, weeks, or sometimes permanently, despite the drug wearing off in a matter of hours; and small injections of saline into the soft tissue between vertebrae produces local pain that radiates into the phantom limb for ten minutes or so and may be followed by hours, weeks or even longer of partial or total relief from phantom pain. Vigorous vibration or electrical stimulation of the stump, or current from electrodes surgically implanted onto the spinal cord, all produce relief in some patients.

Mirror box therapy produces the illusion of movement and touch in a phantom limb which in turn may cause a reduction in pain.

Paraplegia, the loss of sensation and voluntary motor control after serious spinal cord damage, may be accompanied by girdle pain at the level of the spinal cord damage, visceral pain evoked by a filling bladder or bowel, or, in five to ten per cent of paraplegics, phantom body pain in areas of complete sensory loss. This phantom body pain is initially described as burning or tingling, but may evolve into severe crushing or pinching pain, or the sensation of fire running down the legs or of a knife twisting in the flesh. Onset may be immediate or may not occur until years after the disabling injury. Surgical treatment rarely provides lasting relief.

There are a number of ways to classify low back pain with no consensus that any one method is best. There are three general types of low back pain by cause: mechanical back pain (including nonspecific musculoskeletal strains, herniated discs, compressed nerve roots, degenerative discs or joint disease, and broken vertebra), non-mechanical back pain (tumors, inflammatory conditions such as spondyloarthritis, and infections), and referred pain from internal organs (gallbladder disease, kidney stones, kidney infections, and aortic aneurysm, among others). Mechanical or musculoskeletal problems underlie most cases (around 90% or more), and of those, most (around 75%) do not have a specific cause identified, but are thought to be due to muscle strain or injury to ligaments. Rarely, complaints of low back pain result from systemic or psychological problems, such as fibromyalgia and somatoform disorders.

Low back pain may be classified based on the signs and symptoms. Diffuse pain that does not change in response to particular movements, and is localized to the lower back without radiating beyond the buttocks, is classified as "nonspecific", the most common classification. Pain that radiates down the leg below the knee, is located on one side (in the case of disc herniation), or is on both sides (in spinal stenosis), and changes in severity in response to certain positions or maneuvers is "radicular", making up 7% of cases. Pain that is accompanied by red flags such as trauma, fever, a history of cancer or significant muscle weakness may indicate a more serious underlying problem and is classified as "needing urgent or specialized attention".

The symptoms can also be classified by duration as acute, sub-chronic (also known as sub-acute), or chronic. The specific duration required to meet each of these is not universally agreed upon, but generally pain lasting less than six weeks is classified as "acute", pain lasting six to twelve weeks is "sub-chronic", and more than twelve weeks is "chronic". Management and prognosis may change based on the duration of symptoms.

Radiculopathy, also commonly referred to as pinched nerve, refers to a set of conditions in which one or more nerves are affected and do not work properly (a neuropathy). This can result in pain (radicular pain), weakness, numbness, or difficulty controlling specific muscles.

In a radiculopathy, the problem occurs at or near the root of the nerve, shortly after its exit from the spinal cord. However, the pain or other symptoms often radiate to the part of the body served by that nerve. For example, a nerve root impingement in the neck can produce pain and weakness in the forearm. Likewise, an impingement in the lower back or lumbar-sacral spine can be manifested with symptoms in the foot.

The radicular pain that results from a radiculopathy should not be confused with referred pain, which is different both in mechanism and clinical features.

"Polyradiculopathy" refers to the condition where more than one spinal nerve root is affected.

Thoracic spinal pain was significantly associated with: concurrent musculoskeletal pain; growth and physical; lifestyle and social; backpack; postural; psychological; and environmental factors. Specific risk factors identified in adolescents included age (being older) and poorer mental health.

Radiculopathy is a diagnosis commonly made by physicians in primary care specialities, chiropractic, orthopedics, physiatry, and neurology. The diagnosis may be suggested by symptoms of pain, numbness, and weakness in a pattern consistent with the distribution of a particular nerve root. Neck pain or back pain may also be present. Physical examination may reveal motor and sensory deficits in the distribution of a nerve root. In the case of cervical radiculopathy, Spurling's test may elicit or reproduce symptoms radiating down the arm. In the case of lumbosacral radiculopathy, a Straight leg raise maneuver may exacerbate radiculopathic symptoms. Deep tendon reflexes (also known as a Stretch reflex) may be diminished or absent in areas innervated by a particular nerve root.

For further workup, the American College of Radiology recommends that projectional radiography is the most appropriate initial study in all patients with chronic neck pain. Two additional diagnostic tests that may be of use are magnetic resonance imaging and electrodiagnostic testing. Magnetic resonance imaging (MRI) of the portion of the spine where radiculopathy is suspected may reveal evidence of degenerative change, arthritic disease, or another explanatory lesion responsible for the patient's symptoms. Electrodiagnostic testing, consisting of NCS (Nerve conduction study) and EMG (Electromyography), is also a powerful diagnostic tool that may show nerve root injury in suspected areas. On nerve conduction studies, the pattern of diminished Compound muscle action potential and normal sensory nerve action potential may be seen given that the lesion is proximal to the Posterior root ganglion. Needle EMG is the more sensitive portion of the test, and may reveal active denervation in the distribution of the involved nerve root, and neurogenic-appearing voluntary motor units in more chronic radiculopathies. Given the key role of electrodiagnostic testing in the diagnosis of acute and chronic radiculopathies, the American Association of Neuromuscular & Electrodiagnostic Medicine has issued evidence-based practice guidelines, for the diagnosis of both cervical and lumbosacral radiculopathies. The American Association of Neuromuscular & Electrodiagnostic Medicine has also participated in the Choosing Wisely Campaign and several of their recommendations relate to what tests are unnecessary for neck and back pain.

There are various types of sensations that may be felt:

- Sensations related to the phantom limb's posture, length and volume e.g. feeling that the phantom limb is behaving just like a normal limb like sitting with the knee bent or feeling that the phantom limb is as heavy as the other limb. Sometimes, an amputee will experience a sensation called telescoping. This is the feeling that the phantom limb is gradually shortening over time.

- Sensations of movement (e.g. feeling that the phantom foot is moving).

- Sensations of touch, temperature, pressure and itchiness. Many amputees report of feeling heat, tingling, itchiness, and pain.

Coccydynia is also known as coccygodynia, coccygeal pain, coccyx pain, or coccalgia.

Phantom pain involves the sensation of pain in a part of the body that has been removed.

Myofascial pain is pain in muscles or fascia (a type of connective tissue that surrounds muscles). It can occur in distinct, isolated areas of the body. Because any muscle or fascia in the body may be affected, this may cause a variety of localized symptoms.

Generally speaking, the muscular pain is steady, aching, and deep. Depending on the case and location the intensity can range from mild discomfort to excruciating and "lightning-like".

LA SKIN'S DIAGNOSTIC CRITERIA:

- Unilateral pain

- Muscle tenderness

- Clicking sound

- Limitations in jaw function

Knots may be visible or felt beneath the skin. The pain does not resolve on its own, even after typical first-aid self-care such as ice, heat, and rest.

ATN pain can be described as heavy, aching, stabbing, and burning. Some sufferers have a constant migraine-like headache. Others may experience intense pain in one or in all three trigeminal nerve branches, affecting teeth, ears, sinuses, cheeks, forehead, upper and lower jaws, behind the eyes, and scalp. In addition, those with ATN may also experience the shocks or stabs found in type 1 TN.

Many TN and ATN patients have pain that is "triggered" by light touch on shifting trigger zones. ATN pain tends to worsen with talking, smiling, chewing, or in response to sensations such as a cool breeze. The pain from ATN is often continuous, and periods of remission are rare. Both TN and ATN can be bilateral, though the character of pain is usually different on the two sides at any one time.

One way of classifying coccydynia is whether the onset was traumatic versus non-traumatic. In many cases the exact cause is unknown and is referred to as idiopathic coccydynia.

Coccydynia is a fairly common injury which can often result from falls, particularly in leisure activities such as cycling and skateboarding.

Coccydynia is often reported following a fall or after childbirth. In some cases, persistent pressure from activities like bicycling may cause the onset of coccyx pain. Coccydynia due to these causes usually is not permanent, but it may become very persistent and chronic if not controlled. Coccydynia may also be caused by sitting improperly thereby straining the coccyx.

Rarely, coccydynia is due to the undiagnosed presence of a sacrococcygeal teratoma or other tumor in the vicinity of the coccyx.

This disorder is characterized by episodes of severe facial pain along the trigeminal nerve divisions. The trigeminal nerve is a paired cranial nerve that has three major branches: the ophthalmic nerve (V), the maxillary nerve (V), and the mandibular nerve (V). One, two, or all three branches of the nerve may be affected. Trigeminal neuralgia most commonly involves the middle branch (the maxillary nerve or V) and lower branch (mandibular nerve or V) of the trigeminal nerve.

An individual attack usually lasts from a few seconds to several minutes or hours, but these can repeat for hours with very short intervals between attacks. In other instances, only 4-10 attacks are experienced daily. The episodes of intense pain may occur paroxysmally. To describe the pain sensation, people often describe a trigger area on the face so sensitive that touching or even air currents can trigger an episode; however, in many people, the pain is generated spontaneously without any apparent stimulation. It affects lifestyle as it can be triggered by common activities such as eating, talking, shaving and brushing teeth. The wind, chewing, and talking can aggravate the condition in many patients. The attacks are said by those affected to feel like stabbing electric shocks, burning, sharp, pressing, crushing, exploding or shooting pain that becomes intractable.

The pain also tends to occur in cycles with remissions lasting months or even years. 1–6% of cases occur on both sides of the face but extremely rare for both to be affected at the same time. This normally indicates problems with both trigeminal nerves, since one serves strictly the left side of the face and the other serves the right side. Pain attacks are known to worsen in frequency or severity over time, in some people. Pain may migrate to other branches over time but in some people remains very stable.

Rapid spreading of the pain, bilateral involvement or simultaneous participation with other major nerve trunks (such as Painful Tic Convulsif of nerves V & VII or occurrence of symptoms in the V and IX nerves) may suggest a systemic cause. Systemic causes could include multiple sclerosis or expanding cranial tumors.

The severity of the pain makes it difficult to wash the face, shave, and perform good oral hygiene. The pain has a significant impact on activities of daily living especially as people live in fear of when they are going to get their next attack of pain and how severe it will be. It can lead to severe depression and anxiety.

However, not all people will have the symptoms described above and there are variants of TN. One of which is atypical trigeminal neuralgia ("trigeminal neuralgia, type 2" or trigeminal neuralgia with concomitant pain ), based on a recent classification of facial pain. In these instances there is also a more prolonged lower severity background pain that can be present for over 50% of the time and is described more as a burning or prickling, rather than a shock.

Trigeminal neuropathic pain is similar to TN2 but can have the electric pulses associated with classic TN. The pain is usually constant and can also give off a tingling, numbness sensation. This pain is due to unintentional damage to one or more of the trigeminal nerves from trauma, oral surgery, dentistry work, etc. It is difficult to treat but sufferers are usually given the same anticonvulsant and tricyclics antidepressant medicines as with the other types of neuralgias. Surgical options are DREZ (dorsal root entry zone) lesion and MCS or Motor Cortex Stimulation.

TN needs to be distinguished from other forms of unilateral pain which are related to damage to the trigeminal nerve by trauma to the face or dental treatments. This is often termed painful trigeminal neuropathy or post-traumatic neuropathy as some sensory changes can be noted e.g. decrease in pain sensation or temperature. This is important as different care pathways are used. Trigeminal pain can also occur after an attack of herpes zoster, and post-herpetic neuralgia has the same manifestations as in other parts of the body. Trigeminal deafferentation pain (TDP), also termed anesthesia dolorosa, is from intentional damage to a trigeminal nerve following attempts to surgically fix a nerve problem. This pain is usually constant with a burning sensation and numbness. TDP is very difficult to treat as further surgeries are usually ineffective and possibly detrimental to the person.

Hyperalgesia can be experienced in focal, discrete areas, or as a more diffuse, body-wide form. Conditioning studies have established that it is possible to experience a learned hyperalgesia of the latter, diffuse form.

The focal form is typically associated with injury, and is divided into two subtypes:

- "Primary hyperalgesia" describes pain sensitivity that occurs directly in the damaged tissues.

- "Secondary hyperalgesia" describes pain sensitivity that occurs in surrounding undamaged tissues.

Opioid-induced hyperalgesia may develop as a result of long-term opioid use in the treatment of chronic pain. Various studies of humans and animals have demonstrated that primary or secondary hyperalgesia can develop in response to both chronic and acute exposure to opioids. This side effect can be severe enough to warrant discontinuation of opioid treatment.

Hyperalgesia ( or ; 'hyper' from Greek ὑπέρ (huper, “over”), '-algesia' from Greek algos, ἄλγος (pain)) is an increased sensitivity to pain, which may be caused by damage to nociceptors or peripheral nerves. Prostaglandins E and F are largely responsible for sensitizing the nociceptors. Temporary increased sensitivity to pain also occurs as part of sickness behavior, the evolved response to infection.

Atypical trigeminal neuralgia (ATN), or type 2 trigeminal neuralgia, is a form of trigeminal neuralgia, a disorder of the fifth cranial nerve. This form of nerve pain is difficult to diagnose, as it is rare and the symptoms overlap with several other disorders. The symptoms can occur in addition to having migraine headache, or can be mistaken for migraine alone, or dental problems such as temporomandibular joint disorder or musculoskeletal issues. ATN can have a wide range of symptoms and the pain can fluctuate in intensity from mild aching to a crushing or burning sensation, and also to the extreme pain experienced with the more common trigeminal neuralgia.

Recurrent pain is pain that arises periodically and can result in absences from school, outside activities, etc. This type of pain may be the most common.

Descriptions are:

- periodic instead of persistent

- consisting of tension and migraine headaches

- abdominal pains

- chest pain and limb pains

Understanding the meaning of signs and symptoms for the clinical syndrome of lumbar stenosis requires an understanding of what the syndrome is, and the prevalence of the condition. A recent review on lumbar stenosis in the Journal of the American Medical Association's "Rational Clinical Examination Series" emphasized that the syndrome can be considered when lower extremity pain occurs in combination with back pain. This syndrome occurs in 12% of older community dwelling men and up to 21% of those in retirement communities.

The leg symptoms in lumbar spinal stenosis (LSS) are similar to those found with vascular claudication, giving rise to the term pseudoclaudication. These symptoms include pain, weakness, and tingling of the legs, which may radiate down the leg to the feet. Additional symptoms in the legs may be fatigue, heaviness, weakness, a sensation of tingling, pricking, or numbness and leg cramps, as well as bladder symptoms. Symptoms are most commonly bilateral and symmetrical, but they may be unilateral; leg pain is usually more troubling than back pain.

Pseudoclaudication, now referred to as neurogenic claudication, typically worsen with standing or walking and improve with sitting. The occurrence is often related to posture and lumbar extension. Lying on the side is often more comfortable than lying flat, since it permits greater lumbar flexion. Vascular claudication can resemble spinal stenosis, and some individuals experience unilateral or bilateral symptoms radiating down the legs rather than true claudication.

The first symptoms of stenosis include bouts of low back pain. After a few months or years, this may progress to claudication. The pain may be radicular, following the classic neurologic pathways. This occurs as the spinal nerves or spinal cord become increasingly trapped in a smaller space within the canal. It can be difficult to determine whether pain in the elderly is caused by lack of blood supply or stenosis; testing can usually differentiate between them but patients can have both vascular disease in the legs and spinal stenosis.

Among people with lower extremity pain in combination with back pain, lumbar stenosis as the cause is two times more likely in those older than 70 years of age while those younger than 60 years it is 0.40 as likely. The character of the pain is also useful. When the discomfort does not occur while seated, the likelihood of LSS increases considerably around 7.4 times. Other features increasing the likelihood of lumbar stenosis are improvement in symptoms on bending forward 6.4 times, pain that occurs in both buttocks or legs 6.3 times, and the presence of neurogenic claudication 3.7 times. Alternately, the absence of neurogenic claudication makes lumbar stenosis much less likely as the explanation for the pain.

Pain management in children is defined as the assessment then treatment of pain in infants and children. According to Stanford Children's Hospital, pain is a sensation of discomfort, distress or agony. In physiological terms, pain can induce nerve stimulation and conduction of nerve impulses to the brain. Stimulations can be mild, localized, chronic, acute or agonizing. Similar to adults, a child's pain is often tied to emotional and psychological components. Untreated pain can greatly increase the chances of further complications and even death. With this being said, it is important to identify the cause of pain quickly in order to avoid detrimental consequences. There is even a possibility that children can have significant pain related to Epidermolysis Bullosa, Osteogenesis Imperfecta, cancer, metabolic/neurologic diseases, palliative care, and sickle cell disease. A clinician described the use of evidence-based approaches to managing pain in children: "Pain management practices should be based on scientific facts or agreed best practices, not on personal beliefs or opinion. The burden of proof lies with the healthcare professional, NOT the patient." Unfortunately, many of the problems that cause children pain are undertreated.

Atypical facial pain (AFP) is a type of chronic facial pain which does not fulfill any other diagnosis. There is no consensus as to a globally accepted definition, and there is even controversy as to whether the term should be continued to be used. Both the International Headache Society (IHS) and the International Association for the Study of Pain (IASP) have adopted the term persistent idiopathic facial pain (PIFP) to replace AFP. In the 2nd Edition of the International Classification of Headache Disorders (ICHD-2), PIFP is defined as "persistent facial pain that does not have the characteristics of the cranial neuralgias [...] and is not attributed to another disorder." However, the term AFP continues to be used by the World Health Organization's 10th revision of the International Statistical Classification of Diseases and Related Health Problems and remains in general use by clinicians to refer to chronic facial pain that does not meet any diagnostic criteria and does not respond to most treatments.

The main features of AFP are: no objective signs, negative results with all investigations/ tests, no obvious explanation for the cause of the pain, and a poor response to attempted treatments. AFP has been described variably as a medically unexplained symptom, a diagnosis of exclusion, a psychogenic cause of pain (e.g. a manifestation of somatoform disorder), and as a neuropathy. AFP is usually burning and continuous in nature, and may last for many years. Depression and anxiety are often associated with AFP, which are either described as a contributing cause of the pain, or the emotional consequences of suffering with unrelieved, chronic pain. For unknown reasons, AFP is significantly more common in middle aged or elderly people, and in females.

Atypical odontalgia (AO) is very similar in many respects to AFP, with some sources treating them as the same entity, and others describing the former as a sub-type of AFP. Generally, the term AO may be used where the pain is confined to the teeth or gums, and AFP when the pain involves other parts of the face. As with AFP, there is a similar lack of standardization of terms and no consensus regarding a globally accepted definition surrounding AO. Generally definitions of AO state that it is pain with no demonstrable cause which is perceived to be coming from a tooth or multiple teeth, and is not relieved by standard treatments to alleviate dental pain.

Depending upon the exact presentation of atypical facial pain and atypical odontalgia, it could be considered as craniofacial pain or orofacial pain. It has been suggested that, in truth, AFP and AO are umbrella terms for a heterogenous group of misdiagnosed or not yet fully understood conditions, and they are unlikely to each represent a single, discrete condition.