Where does it hurt? Understanding low back pain

Principles of low back pain
While 90% of people afflicted by low back pain will recover completely within about six weeks –for the 10% of patients who do not recover within a few weeks, low back pain can be a painful, prolonged, costly and frustrating experience. The underlying causes of low back pain (sometimes referred to as lumbago) can be complex and are not always readily apparent. This article is aimed at helping patients understand how physicians evaluate the area of pain distribution in helping to diagnose the source of a patient’s low back pain and determine initial treatment options.

Before discussing the specific types of low back pain, it is important to understand a few important principles.

Pain does not always equate to tissue damage. The severity of pain from low back problems is often unrelated to the extent of physical damage present. For example, a simple pulled muscle in the low back can cause excruciating pain that can limit one’s ability to walk or even stand, whereas a even a large herniated disc can be completely painless.
Diagnosis is often difficult. There are many anatomical structures in the low back that can cause severe lower back pain and/or pain that radiates into the legs and/or feet. These include:

Soft tissues, such as muscles, ligaments and tendons
Bones, which provide the structural building blocks of the spinal column
Facet joints, which allow the spine move
Discs (the outer rim of the disc, the annulus, can be a source of significant low back pain due to its rich nerve supply and tendency towards getting damaged)
Nerves, which branch out from the spinal cord in the low back and innervate the legs and feet

All of the above structures are interwoven to make up the structure of the spine. During embryological development there is a great deal of overlap of nerve supply to all of these structures making it nearly impossible for the brain to distinguish between problems with one structure versus another. For example, a torn or herniated disc can feel identical to a bruised muscle or torn ligament.

Diagnostic accuracy is important. Getting an accurate diagnosis as to the underlying cause of one’s pain is important. For example, it’s not enough to know that one has sciatica – it is also important to determine the underlying cause of the sciatica, such as a herniated disc or spinal stenosis, in order to determine the best treatment options.
Low back pain is a personal experience. Unlike many other medical conditions, the experience of low back pain is not the same for everyone. For example, two people can have the exact same condition but for one it is incapacitating and for the other it is a mere nuisance. In fact, for most people a spinal abnormality (such as a degenerated disc that can be seen on an MRI scan) is painless. Other factors - both physical and psychological - often contribute to a person’s experience of low back pain.

Diagnosing the cause of low back pain
When determining the underlying cause of low back pain, both the type of low back pain (a description of how the pain feels) and the area of pain distribution (where the pain is felt) help guide the physician in making a preliminary diagnosis and determining the appropriate treatment plan.

Getting an accurate diagnosis of the cause of low back pain is often more challenging than many people expect and often will involve a combination of a thorough patient history and physical exam as well as diagnostic tests. The history and physical exam are used to help determine if a patient’s lower back pain is more likely to be caused by a soft tissue (muscle, ligament or tendon) problem that will likely heal itself or a more serious underlying medical condition, such as fracture, infection or tumor. By the time a physician orders any diagnostic tests such as an x-ray or MRI scan, he or she will usually have a strong suspicion as to the probable cause of the patient’s low back pain and the diagnostic test is used to confirm it and provide more detail.

It is important to note that patients with the following symptoms could have a serious medical condition and should be evaluated immediately:

Fever and chills
History of cancer with recent weight loss (or unexplained weight loss)
Severe trauma
Significant leg weakness
Sudden bowel and/or bladder incontinence – either difficulty passing urine or having a bowel movement, or loss of control of urination or bowel movement
Severe, continuous abdominal pain and back pain

This article reviews three classifications of low back pain based on the area of pain distribution, or where the pain is felt (e.g. confined to the low back or radiating down the leg). The three classifications are: