There are many different causes for low back pain. The most common causes are mechanical in nature, this means that there is a disruption to the normal functioning of the anatomical components of the low back. The list below includes some of the most common mechanical causes of low back pain as well as some non-mechanical causes.
Bones, Muscles and Joints
Muscle Strain – when a muscle is stretched beyond its normal limits. This can sometimes cause the muscle to tear, damaging the muscle. A muscle strain is usually a result of overuse, fatigue or improper use of a muscle. It can happen suddenly or it can develop slowly over time.
Ligament Sprain – ligaments are strong supportive tissues that are located around joints. They act as a supportive structure around a joint, that aid in improving stability of the joint. A sprain occurs when the ligament is overstretched. Sometimes tearing can occur, this is known as a ligament rupture.
Facet Joint Dysfunction – the spinal column is made up of 33 spinal vertebrae that are connected together by facet joints. The joints have cartilage between the bones and are supported by an abundance of ligaments, including a capsular ligament. Within the capsular ligament there is a fluid known as synovial fluid which aids in the smooth moving of the joint. The capsule, ligaments and joints are highly innervated. Through injury, trauma, poor posture and many other reasons these joints can be affected and cause pain, on their own or in conjunction with the intervertebral discs.
Spondylolithesis – when one of the vertebrae in the low back, moves out of its usual / normal position, usually slipping forwards. This causes instability within the spine. If the bone slips too much it may compress onto the surrounding nerves causing pain and neurological symptoms down the legs.
Sacroiliac Joint (SIJ) Dysfunction – the sacroiliac joint is located at the base of the spine, where the spine meets each side of the pelvis. It is a very strong joint that absorbs a lot of force created from the upper and lower body. The SIJ doesn’t have much range of motion and can become painful if there is too much motion or too little motion. It can also become painful if it becomes inflamed, this is known as sacroiliitis.
Changes Associated with Age
Spondylosis – is another term to describe osteoarthritis of the spine. It is the age related changes that occur to the spinal column, including the discs and facet joint. As these changes occur they can cause pain, inflammation and instability within the joint. In some cases it can cause a narrowing of the spinal canal (stenosis).
Degenerative Disc Disease – this is an age related condition in which one or more of the intervertebral discs within the spinal column lose their ability to act as a cushioning for the spine. As a consequence they become weaker and develop tears. In some cases it can also cause the spinal canal to narrow. This is referred to as stenosis
Osteoporosis – this is a condition in which there is weakening of the bones due to a reduction in bone density. There is greater prevalence in the elderly but can also be a result of some endocrine and metabolic diseases. Due to the reduction in bone density compression fractures are common which can sometimes cause pain. However, pain is more likely to be caused due to there being compression onto neurological structures as a result of the compression fracture.
Nerve and Spinal Cord Problems
Lumbar Herniated Disc – intervertebral discs act as a cushion, aiding (along with muscles & ligaments) in holding the spinal vertebrae together. The discs help prevent the vertebrae from rubbing together & consists of a gel filled inner layer surrounded by a hard fibrous outer layer. Sometimes a person can injure or strain their discs causing part of the gel filled nucleus to herniate out of the fibrous outer casing. This is known as a herniated disc, prolapsed disc or a slipped disc. When the disc herniation occurs in the low back it may compress onto the sciatic nerve causing symptoms into the buttock, thigh, leg and/ or foot.
Spinal Stenosis – this is a condition in which there is narrowing of the spinal canal. There are many different causes of spinal stenosis, such as injury, trauma and degenerative changes.
Less Common Causes of Low Back Pain
Infection – spinal infection is very rare, but can cause severe pain and can be lifethreathning if it is left untreated. Also known as osteomyelitis it can be caused by; bacteria in the bloodstream, infectious disease that spreads to the bone, infection from recent surgery or injection in or around a bone.
Tumors – Tumours in the spine are not very common, however if they do appear they usually start elsewhere in the body and metastasize to the spine. The most common tumours that metastasize to the spine start from cancers in the prostate, kidney, lung, breast and thyroid.
Autoimmune diseases – back pain is a common symptom in individuals suffering from autoimmune conditions such as ankylosing spondylitis, rheumatoid arthritis, lupus and crohn’s disease.