Why does the distinction really matter on pain?  Pain is pain isn't it?

       No is the answer and the distinction matters as it relates many  times to whether the condition will be paid for by insurance or not.  Also pain can be a symptom as well as a diagnosis.  Chronic pain differentiates itself as a diagnosis simply because it is truly a symptom, not a diagnosis, but when the symptom can not be treated then it becomes the diagnosis.   Most diagnosis are for the underlying cause such as diabetes, arthritis, staph infection, or cancer.   The diagnosis allows treatment to begin for a known, not an unknown as chronic pain is.

Chronic Pain

Chronic pain is pain that last a long time. Some discomfort that has been going on for a long time.   
As an example Medicare, H.C.F.A., will pay for tens units rental and purchase only if the patient is suffering from chronic pain.  Chronic pain is defined by Medicare as pain for 3 or more months.   The essence of that requirement is to say that conventional treatments for the symptom of pain have failed and now the actual diagnosis of "chronic pain" is an admission that the symptom has become the diagnosis.   This is a rarity in medicine. 

Acute Pain   

Most pain, such as acute, is merely a symptom of an injury and as the underlying cause, example sprained ankle, is healed and rehabbed so the symptom of pain goes away.   The physician knows the reason for the symptom and treats or prescribes medications that allow the causative agent of pain to return to normal thus the pain goes away, ie the sprained ankle heals and all soft tissue damage is restored to normal.  

The Drawbacks of   Traditional Treatments

There is a growing dissatisfaction with the solutions offered by the medical community. Unfortunately for chronic pain many times the treatment such as surgery may exacerbate the pain or fails to remove the cause of the pain.   When that happens the patient may actually be prescribed mind altering medications that no longer allow the perception of pain to be felt but in many situations the pain impulse is there but the patient is now sleeping more, drowsy, or limiting activities due to the pain impulses.   It is at this point that many patients refuse more  traditional medical treatments such as muscle relaxant drugs, surgery, opioid derived pain meds and look for alternative means of pain control.  Generally speaking chronic pain requires the patient to  shield themselves from doing activities such as walking, working, or any form of exericse such as gardening because to do so exacerbates the pain.   As a result of the inactivity other parts of the patient's body are now inactive and the chronic pan becomes worse as now the inactivity has created more areas that are deprived of motion/movement and secondary pain issues evolve.  An example of secondary pain is the person who suffers from "chronic low back pain" and if improperly treated it often develops a secondary pain called "radiating sciatica".  The secondary pain, pain shooting down the leg, can often be corrected and eliminated but once done then the primary diagnosis "chronic low back pain" remains and much care must be taken to make sure the old "radiating sciatica" pain, acute now, does not return.

    Chronic pain is complicated and unfortunately the acceptance of the diagnosis iteself is an admission that to that point in time nothing has worked therefore the medical profession has admitted the cause can not be determined so the state of pain is declared permanent simply by allowing the diagnosis of a symptom to become the diagnosis.