Back pain – disc problems

What are intervertebral discs?#

The term “disc” is short for “intervertebral disc”. These are the spongy cushions that separate the bones of the spine (the vertebrae). Discs absorb shock, keep the spine stable, and give the vertebrae pivot points that allow movement.

Each disc has two parts: an elastic outer shell (the annulus fibrosis) and an inner jelly-like substance (the nucleus pulposus). The outer shell surrounds and holds the inner jelly within the core of the disc. Discs can handle a lot of pressure without problems, but certain kinds of load can strain and irritate the outer shell. In some cases this pushes the contents outward, which is known as a disc protrusion.

Disc changes with age#

Discs change throughout life as connective tissues age and the spine adapts to the physical loads of daily living. Disc bulges, narrowing of the disc space (loss of disc height) and disc dehydration are normal, common age-related changes. They often show up on an x-ray or scan even in healthy people who have no back pain.

The discs of a young child are plump and moist (well hydrated). With age, their water content reduces until they become comparatively thin and hard. This normal ageing is thought to increase friction between the bones, which can lead to growths around the discs called bone spurs.

These age-related changes often cause no problems, but some people do experience pain. When they do, the changes are often called “degenerative disc disease”. The most common symptom is back pain that can be made worse by activity or by prolonged sitting. Interestingly, the risk of a disc protrusion actually falls as we get older, because the discs dry out and their contents are less able to ooze through any weakened areas in the outer shell.

Symptoms#

The symptoms of an irritated disc vary according to its location and severity. Scans are often unhelpful for working out whether back pain is coming from a disc, because discs change with age and use anyway. Possible symptoms include:

• back pain
• increased back pain when repeatedly bending, or with prolonged sitting
• increased back pain with coughing, sneezing, laughing or straining
• numbness or pins-and-needles radiating into an arm or leg, if a disc has irritated a nearby nerve

Risk factors#

Some people are more prone to disc problems than others. Risk factors include:

• obesity or an elevated body mass index
• lifting heavy loads
• lack of fitness and lack of regular exercise
• cigarette smoking
• older age
• poor posture
• diabetes

Often, though, disc changes develop without any recognizable risk factor.

Types of disc problems#

• Disc strains and sprains. Like strains and sprains elsewhere in the body, applying sustained or excessive load to soft tissues such as ligaments, tendons or muscles can cause irritation and inflammation. This may not show on x-rays or scans.
• Degenerative disc disease. The age-related disc changes described above. These can also be found in people who have no symptoms.
• Disc protrusion. A “slipped disc” is an inaccurate term still sometimes used for this. Discs do not actually slip out of place; they are held firmly by ligaments, muscles and the vertebrae. Terms like “protruded”, “herniated”, “extruded”, “bulged” or “prolapsed” are more accurate. The real problem is that a small area of the tough outer shell weakens, allowing the soft jelly-like contents to ooze out. When this contacts nearby structures, especially spinal nerves, it can alter nerve function, causing numbness or pins-and-needles. The most common site is the lower back.
• Sciatica. Nerve pain caused by irritation of the sciatic nerve. The pain radiates from the spine into the buttock, the back of the thigh, the leg and the sole of the foot, and is often associated with altered sensation such as pins-and-needles or numbness in the affected limb. Disc protrusion is a common cause. Spinal nerves normally have room to slide as the body moves, but a disc bulge can press against them and hamper their movement, and leaking disc contents can cause local chemical irritation or inflammation.

Diagnosis#

Diagnosing disc problems involves:

• taking a medical history, to find predisposing risk factors and conditions and to identify any spinal nerve involvement
• doing a physical examination

Further investigations are usually carried out only if symptoms persist for more than six weeks despite staying active, or if there is concern that the disc is affecting a spinal nerve.

Treatment#

Most disc problems resolve with time regardless of treatment, just like soft tissue sprains elsewhere in the body. Short-term bed rest for a few days may help in the early management of severe sciatica, but most people can stay active within their pain limits, which along with appropriate pain relief is usually the best approach. Options include:

• pain-relieving medications, including non-steroidal anti-inflammatory drugs (NSAIDs) or steroids
• heat treatment, such as heat wraps or hot packs
• gradually increasing activity levels within pain limits
• an exercise program designed to improve strength, flexibility and fitness
• a short-term (less than 12 weeks) trial of massage, spinal mobilization or manual therapy
• surgery in some cases, to trim the protruding disc and relieve pressure on the affected nerve; in severe degenerative disc disease, surgery may be considered to remove the disc and fuse the two vertebrae on either side

Severe cases of both sciatica and degenerative disc disease are uncommon, and most disc protrusions heal on their own and reduce in size over time.

Self-help#

Ongoing self-management may help reduce the risk of future disc problems. Be guided by your doctor or health professional, but general suggestions include:

• avoid a sedentary lifestyle and stay physically active
• avoid lifting objects that are too heavy for you; remember that bending and twisting (especially together) increase the load on discs
• address posture issues if certain postures, such as while sitting or walking, bring on your pain
• maintain good overall fitness and muscle strength in your arms, legs and trunk
• do a program of back-strengthening exercises
• include regular flexibility exercise such as Pilates, walking, tai chi or yoga, which can improve mobility and reduce muscle tension; find something you enjoy and can do regularly

Other causes of back pain#

There are other causes of back pain, so see your doctor if pain is strong, persistent or continues through the night. Other causes include:

• Muscular pain – common, usually does not spread into the legs, and very likely to resolve on its own without specific treatment.
• Fractures – more common in older people, people with osteoporosis, and people taking medications that cause bone loss (such as steroids or anti-seizure/epilepsy medications). They can also follow direct injury or trauma, such as a motor vehicle accident.
• Cancer – some cancers can cause back pain. See your doctor if you have strong pain, persistent pain, night pain, unexpected weight or appetite loss, a previous cancer diagnosis elsewhere in the body, or any other symptoms that concern you.
• Infection – can occur after invasive procedures such as surgery or dental work, and in people who are immune suppressed or who inject illicit drugs. Warning symptoms include strong pain, night pain, fevers, sweats, fatigue, and unexpected weight and appetite loss.
• Ankylosing spondylitis – causes gradual onset of persistent back pain and stiffness that is worse in the morning. It usually affects young men more than women. The pain is typically relieved by movement rather than rest and often causes overnight pain and sleep disturbance. If you have this pattern, see your doctor for a referral to a rheumatologist.
• Scoliosis – increased curvature of the spine. It may be present from birth, develop with increasing age, or arise in people with increased soft tissue elasticity (hypermobility). Children and adolescents with scoliosis should see their doctor for a referral to a spinal surgeon experienced in assessing and managing it, particularly if it is getting worse.

Key points#

• Disc bulges, disc space narrowing and disc dehydration are normal, common age-related changes that often cause no symptoms.
• Symptoms of an irritated disc vary with its location and severity, and scans are often unhelpful for diagnosis.
• Risk factors include obesity, heavy lifting, lack of fitness, smoking, older age, poor posture and diabetes, but disc changes often develop without any recognizable risk factor.
• Most disc problems resolve with time; staying active within pain limits, with appropriate pain relief, is usually the best approach.

Where to get help#