Sciatica is a symptom of a problem with the sciatic nerve, the largest nerve in the body. It controls muscles in the back of your knee and lower leg and provides feeling to the back of your thigh, part of your lower leg, and the sole of your foot. When you have sciatica, you have pain, weakness, numbness, or tingling. It can start in the lower back and extend down your leg to your calf, foot, or even your toes. It's usually on only one side of your body.

Causes of sciatica include

• A ruptured intervertebral disk
• Narrowing of the spinal canal that puts pressure on the nerve, called spinal stenosis
• An injury such as a pelvic fracture.

In many cases no cause can be found.

Sometimes sciatica goes away on its own. Treatment, if needed, depends on the cause of the problem. It may include exercises, medicines, and surgery.

Sciatica is a condition that can lead to pain in the back and legs. It occurs when pain travels along the path of the sciatic nerve. This nerve starts in the lower spine, and travels through the hip and buttock and down the back of the leg to the foot.

There are a range of different causes of sciatica. In most cases, the condition gets better over time, either on its own or with treatment.

Sciatica is a painful condition resulting from inflammation or compression of the sciatic nerve or any of the spinal nerves that contribute to it.

Of the four nerve plexuses, two are found at the cervical level, one at the lumbar level, and one at the sacral level (Figure). The cervical plexus is composed of axons from spinal nerves C1 through C5 and branches into nerves in the posterior neck and head, as well as the phrenic nerve, which connects to the diaphragm at the base of the thoracic cavity. The other plexus from the cervical level is the brachial plexus. Spinal nerves C4 through T1 reorganize through this plexus to give rise to the nerves of the arms, as the name brachial suggests. A large nerve from this plexus is the radial nerve from which the axillary nerve branches to go to the armpit region. The radial nerve continues through the arm and is paralleled by the ulnar nerve and the median nerve. The lumbar plexus arises from all the lumbar spinal nerves and gives rise to nerves enervating the pelvic region and the anterior leg. The femoral nerve is one of the major nerves from this plexus, which gives rise to the saphenous nerve as a branch that extends through the anterior lower leg. The sacral plexus comes from the lower lumbar nerves L4 and L5 and the sacral nerves S1 to S4. The most significant systemic nerve to come from this plexus is the sciatic nerve, which is a combination of the tibial nerve and the fibular nerve. The sciatic nerve extends across the hip joint and is most commonly associated with the condition sciatica, which is the result of compression or irritation of the nerve or any of the spinal nerves giving rise to it.

Nerve Plexuses of the Body There are four main nerve plexuses in the human body. The cervical plexus supplies nerves to the posterior head and neck, as well as to the diaphragm. The brachial plexus supplies nerves to the arm. The lumbar plexus supplies nerves to the anterior leg. The sacral plexus supplies nerves to the posterior leg.

The causes of sciatica include spinal injury or trauma, bone spurs or other growths, narrowing of the spinal canal, or tight or swollen muscles in the buttock. In many cases, people can’t pinpoint a specific injury that caused the condition.

Risk factors for sciatica include:

• age-related changes to the spine
• obesity, which can put extra pressure on the spine
• occupations where you twist the spine or pick up heavy loads
• prolonged sitting
• diabetes, which can increase the risk of nerve damage

Symptoms of sciatica can include pain, tingling and numbness in the leg.

Sciatica is felt as nerve pain radiating from the buttock down the back of the leg, often when sitting, sneezing, coughing or going to the toilet. You may also feel lower back pain, and/or tingling, pins and needles, numbness or weakness in your leg.

Although sciatica pain can be severe, most people find their symptoms improve in time. As sciatica is seen as a more serious low back condition, it’s advisable to see your doctor within the first few days of getting the symptoms. To diagnose sciatica, the doctor will take a medical history and examine your spine and legs.

You should seek medical attention immediately if you have problems controlling your bladder or bowels, or have weakness, numbness or severe pain.

The Royal Australian and New Zealand College of Radiologists recommends that an x-ray or other imaging in response to low back pain is only needed if you have other significant symptoms. If you have sciatica, discuss with your doctor whether imaging is required, which it may or may not be, depending on the circumstances. 

The choice of sciatica therapies depends on the length of symptoms and severity of your condition. These therapies include:

• special back care education
• rest
• physical therapies
• medication treatment
• lifestyle changes
• surgery

Mild sciatic usually goes away in time. When you first experience sciatica, 1 or 2 days’ bed rest may be needed. However, it's important to return to activity as soon as possible, to help your spine stay strong.

Sciatica treatment includes pain relief medicines such as paracetamol, anti-inflammatory drugs such as ibuprofen and physiotherapy. Most people with sciatica get better with conservative treatments such as physiotherapy.

You should see your doctor again self-care measures fail to improve your pain, if your pain lasts longer than a week, is severe or becomes progressively worse.

If your symptoms persist, an injection of anaesthetic into the spine may be needed or, in rare cases, surgery.

Looking after your back, managing your weight, and improving your general physical condition can all help prevent sciatica. Doing physical therapy at home, such as muscle strengthening exercise, can help to prevent sciatica coming back.