Starting physical therapy sooner rather than later leads to:

  • Significant reduction in rate of spinal injections (OR=0.46), surgery (OR-0.79), office visits (OR=0.47) (Gellhorn et.al 2012)

  • Reduction in imaging (OR=0.52), spinal injections (OR=0.56), surgery (OR=0.59), opioids (OR=0.62) (Child et al 2015)

  • Total medical costs for LBP were $2736.23 lower for patients receiving early PT (Fritz et al. 2012)


Definition #1: “An unpleasant sensory and emotional experience associated with actual or potential tissue damage”

Definition #2: “A complex constellation of unpleasant sensory, emotional and cognitive experiences provoked by real or perceived tissue damage and manifested by certain autonomic, psychological, and behavioral reactions.”


  • The study of pain has been going through a revolution in the past decade. We now understand that pain is much more than a simple response to injury, which is reflected in the above definitions. The perception of pain is produced by the brain. It happens in 100% of the time! The nervous system functions as an alarm system that is designed to warn you of a potential danger or a threat. The nervous system does it by producing several responses, among them is pain. There are multiple areas in the brain that work together to analyze the information coming from your body to decide if you will or will not experience pain. The decision will be based on whether you are in a potentially dangerous situation or not, which is dependent in part on the context in which you are at, your knowledge of the situation, your past experience, and emotional state. It is modulated by many factors across the somatic, psychological and social domains (see diagrams below). The perception or experience of pain is a part of our body’s alarm system. Pain does NOT always mean that there is tissue injury, and if there is an injury it does NOT reflect the severity of it (more pain ≠ worse injury). In addition, as pain persists (becomes chronic) the relationship between the state of the tissue and pain becomes weaker.

Moseley GL. Reconceptualising pain according to modern pain science. Physical Therapy Reviews 2007;12(3):169–178. doi:10.1179/108331907x223010.



Acute Pain: Pain that is provoked by a specific disease or injury, and is self-limited. Pain is considered “acute pain” when it lasts less than 3 to 6 month.

  • Acute pain is typically localized to the area where the injury occurred and has clear mechanical and anatomical aggravating factors (i.e. you jam your finger- it hurts to move it). It serves as one of the body’s protective mechanisms (part of the alarm system). Typically, acute pain leads to avoiding/withdrawing from the painful area. In the acute phase, an inflammatory reaction will be initiated in the zone of injury and will lead to repair and healing of the injured tissues.

Nociceptors: “A peripherally localized neuron preferentially sensitive to a noxious stimulus or to a stimulus that would become noxious if prolonged.”


Noxious Stimulus: “damaging or potentially damaging stimuli including extremes of temperatures, mechanical stimulation, and allogens that provoke an avoidance response.”


  • In simple words, nociceptors are the sensors located throughout the body that are in charge of detecting and transmitting electrical stimulation in response to a dangerous stimulus. There are two types of nociceptors fibers: A-delta and C fibers. Both are slow conducting fibers, which mean that they transmit electrical messages slower than other types of fibers, for example fibers that lead to a motor response. Nociceptors response to mechanical stimuli (i.e. pressure to your skin, joints, etc.), thermal stimuli (i.e. very hot water or very cold water), and chemical stimuli (i.e. spilling acid on your hand, or inflammatory chemicals after an acute injury).

  • Nociceptors are referred to as “pain receptors” since they have high threshold for activation, which means stronger stimulation is required in order to activate these receptors. Stronger stimulation may be a threat and it requires more careful attention from the brain. In response, you may or may not experience pain (see pain definition above). They play a very important role in warning our body from potential danger at the acute phase of injury (i.e. you need to know when you sprain your ankle or step on a sharp object). However, they are only one piece in the experience of pain. We now understand that one may experience pain without any activation of the “pain receptors”; you can have pain without injury! This is because the experience of pain is produced by the brain, and NOT by pain receptors. This is especially important to understand when it comes to chronic/persistent pain.

(There are multiple areas in the brain that work together to analyze the information coming from your body and decide if you will or will not experience pain)


Delayed Onset of Muscle Soreness (DOMS): This simply refers to muscle soreness that develops a few hours to a few days after physical exertion (e.g. exercise) that challenges your muscles. There are two main theories exercise physiologist suggest about the cause of DOMS. It may be caused by changes in pH levels at the muscle that was being used. The brain is sensitive to changes in pH and therefore, it will let you know about it using soreness/pain sensation. The other theory is that DOMS is caused by micro-tears in the muscles, which initiate an inflammatory response that is detected by the brain and therefore, you feel soreness/pain. The micro-tears are essential to build the muscle and ultimately improve its function. In reality, both mechanisms of DOMS are likely true and take place at the same time. It is important to understand that this is a normal reaction to exercise/activity that challenges your body.




Chronic Pain: pain that lasts beyond the expected time of tissue healing. Pain is considered “chronic pain” when lasts more than 3 to 6 months. “Chronic pain may arise from psychological states, serves no biologic purpose, and has no recognizable end-point.”

  • Chronic pain is considered a disease state by itself. It may or may not be related to a specific injury or illness and may develop spontaneously for unknown reason. The pain lasts long after the tissues have healed. The experience of pain is as a result of false output that is originating from the brain and provokes pain signals in the body without an actual tissue injury. Click here to learn more about pain and chronic pain mechanisms.

Central sensitization: “Any sensory experience greater in amplitude, duration, and spatial extent than that would be expected from a defined peripheral input under normal circumstances, qualifies as potentially reflecting a central amplification due to increased excitation or reduce inhibition. The CNS can change, distort or amplify pain, increasing its duration, and spatial extent in a manner that no longer directly reflect the specific qualities of peripheral noxious stimuli, but rather the particular functional states of circuits in the CNS.”

  • Typically seen with chronic pain conditions, central sensitization is a complex pathological (disease) process that simply means that the nervous system has become more sensitive. The nervous system consists of the peripheral nervous system and the central nervous system. The central nervous system (brain and spinal cord) is connected to the peripheral nervous system (all the other nerves in your body). The increased sensitivity results from abnormal excitation or inhibition of pain-related processes in the nervous system. There is over-activation and release of chemical and signals that increase pain and under-activation of processes that decrease pain. The results are typically persistent pain, hypersensitivity to touch/ temperature/ light/ noise/ pressure, difficulty sleeping, difficulty concentrating, etc. Since central sensitization and chronic pain originate and are produced by the brain, we need to treat them differently than we treat acute injuries. In other words, we need to retrain the brain. We do that using education, exercises for the peripheral and the central nervous systems, graded exposure to previously provocative activities/situations, and lifestyle modifications. In addition, chronic pain conditions and central sensitization are often treated with medications. However, recent studies show that the use of medication for chronic pain conditions, specifically opioids, may be more harmful than good (see the Center of Disease Control (CDC) statement below about opioids for chronic pain).


    (The peripheral and central nervous systems are connected and function as one unit. When the system is hyper-sensitive (central sensitization) you may have pain throughout the body without any injury.

    “It's almost as if somebody came into your home and rewired your walls so that the next time you turned on the light switch, the toilet flushed three doors down, or your dishwasher went on, or your computer monitor turned off.” Dr. Elliot Krane)


Popular Pain Medications

(medications that we see most commonly prescribed to our patients)


  • Percocet- an opioid used to relieve moderate to severe pain. Percocet is a combination of acetaminophen and oxycodone (read more about oxycodone here). Percocet affects the central nervous system to produce an analgesic effect. Therefore, it can cause addiction or dependence even if used at regular doses. Common side effects include upset stomach, dry mouth, constipation, nausea, drowsiness/sleepiness, blurred vision, and dizziness.

  • Tramadol: an opioid used to treat moderate to severe pain. Tramadol acts on the central nervous system in two separate mechanisms (see here) and may cause addiction. Common side effects include nausea, hallucination, itching, constipation, anxiety, agitation, excessive sweating, and diarrhea.

  • Gabapentin- is an antiepileptic and antiseizure drug. It is also used to relieve nerve pain following shingles/herpes virus, as well as other nerve pain conditions such as diabetic neuropathy, peripheral neuropathy, trigeminal neuralgia, etc. It is also used to treat restless legs syndrome. There are many side effects for gabapentin (see here), but among the most common side effects are ataxia, nystagmus (uncontrolled eye movements), fever, dizziness, drowsiness, fatigue, and viral infection.

  • Lyrica- is an antiepileptic medication that works by slowing the impulses in the brain and affects chemicals in the brain that send signals related to pain. It is used to treat of seizures, fibromyalgia, neuropathic pain, and pain associated with spinal cord injury. Due to its influence on the central nervous system, Lyrica may trigger thoughts about suicide (if so, call you physician immediately). Lyrica’s most common side effects are dizziness, fatigue, infection, constipation, weight gain, blurred vision, ataxia (loss of control on body movements), headache, double-vision, drowsiness, tremor, peripheral edema, accidental injury, and dry mouth. 


Center of Disease Control Statement (CDC) about the use of opioids to treat chronic pain.

(This statement was taken from the “CDC Guideline for Prescribing Opioids for Chronic Pain, United States 2016”)

  • “The United States is currently experiencing an epidemic of prescription opioid misuse and overdose. Increased prescribing and sales of opioids—a quadrupling since 1999— helped create and fuel this epidemic.

    The guideline provides recommendations on the use of opioids in treating chronic pain (that is, pain lasting longer than three months or past the time of normal tissue healing). Chronic pain is a public health concern in the United States, and patients with chronic pain deserve safe and effective pain management.  This new guideline is for primary care providers—who account for prescribing nearly half of all opioid prescriptions—treating adult patients for chronic pain in outpatient settings. It is not intended for guiding treatment of patients in active cancer treatment, palliative care, or end-of-life care.

    While prescription opioids can be part of effective pain management, they have serious risks.  The new guideline aims to improve the safety of prescribing and curtail the harms associated with opioids, including opioid use disorder and overdose. The guideline also focuses on increasing the use of other effective treatments available for chronic pain, such as nonopioid medications or physical therapy.

    By using the guideline, primary care physicians can determine if and when to start opioids to treat chronic pain. The guideline also offers specific information on medication selection, dosage, duration, and when and how to reassess progress and discontinue medication if needed. Using this guideline, providers and patients can work together to assess the benefits and risks of opioid use.

    Among the 12 recommendations in the guideline, three principles are key to improving patient care:

    1. Nonopioid therapy is preferred for chronic pain outside of active cancer, palliative, and end-of-life care.

    2. When opioids are used, the lowest possible effective dosage should be prescribed to reduce risks of opioid use disorder and overdose.

    3. Providers should always exercise caution when prescribing opioids and monitor all patients closely.

In developing the guideline, CDC followed a rigorous scientific process using the best available scientific evidence, consulting with experts, and listening to comments from the public and partners. CDC is dedicated to working with partners to improve the evidence base, and will refine recommendations as better evidence is available”.



Recommended Videos:

  1. TEDxAdelaide - Lorimer Moseley - Why Things Hurt  

  2. Understanding Pain in less than 5 minutes, and what to do about it! 

  3. Explaining chronic pain: The role that stress plays and the creation of learned nerve pathways 

  4. Cognitive Functional Therapy with Professor Peter O'Sullivan 

  5. Jack with Peter O'Sullivan