Sciatica: what can cause pain radiating into the leg
Sciatica is one of the most common reasons people consult an orthopaedic specialist. For some, the pain is so severe that sitting, walking or sleeping becomes difficult. This makes it all the more important to understand where the symptoms come from and what can help. There is no single answer, because pain radiating into the leg can have a variety of causes. In this article, we explain the possible causes and how the symptoms can be relieved.
In this article, you will learn
- What sciatica is and how it feels
- How to tell whether the sciatic nerve is really affected
- Which conditions can cause the symptoms
- How sciatica is diagnosed and treated
What is sciatica?
Sciatica occurs when the sciatic nerve or one of its nerve roots is irritated or compressed. The sciatic nerve (nervus ischiadicus) is the thickest and longest nerve in the body. It is formed by nerve roots from the lower lumbar spine and sacrum. The nerve passes through the buttock and down the back of the thigh. Above the back of the knee, it divides into the tibial nerve and the common fibular nerve. Together, these nerves control the muscles of the lower leg and foot and transmit sensations such as touch and pain.
The symptoms are also referred to as sciatic pain. If lower back pain occurs at the same time, the condition is known as lumboischialgia. This is different from lumbago, in which the pain remains confined to the back.
What does sciatica feel like?
Sciatica typically causes a burning, stabbing or electric-shock-like pain that usually travels from one side of the buttock into the leg. Coughing, sneezing or straining often makes it worse because these actions briefly increase the pressure in the spinal canal. Tingling, numbness or a sensation that the leg has “fallen asleep” may also occur.
Each nerve root that leaves the lumbar spine or sacrum supplies a defined area of skin on the leg. The precise location of pain or tingling can therefore indicate where a nerve is irritated. Doctors name nerve roots according to their level, such as L5 for the root at the fifth lumbar vertebra.
If one of these nerve roots is irritated, symptoms are most likely to occur in the following areas:
- L4 (fourth lumbar vertebra): knee and inner side of the lower leg
- L5 (fifth lumbar vertebra): outer side of the lower leg, top of the foot and big toe
- S1 (first sacral vertebra): calf, heel, outer border of the foot and little toe
How can you tell whether the sciatic nerve is really affected?
The crucial distinction is between radicular and pseudoradicular pain.
Radicular pain means that a nerve root itself is irritated. The pain usually extends below the knee, follows a clearly defined path and is often accompanied by tingling, numbness or loss of strength.
Pseudoradicular pain merely resembles this pattern. It originates in joints, ligaments or muscles, tends to spread more diffusely into the buttock and thigh, and usually stops above the knee. There are no neurological deficits. Many symptoms that are commonly described as “sciatica” belong to this group.
What causes sciatica?
From an orthopaedic perspective, the following conditions are the most common causes:
The most common cause is a herniated disc between the fourth and fifth lumbar vertebrae or between the fifth lumbar vertebra and the sacrum. Disc material that has escaped presses on the nerve root and triggers inflammation. A bulging disc can also irritate the nerve root.
Bony growths, thickened ligaments or disc tissue can narrow the spinal canal until the nerve roots come under pressure. If the lower lumbar spine is affected, where the roots of the sciatic nerve run, sciatica may develop in both legs more often than it does with a herniated disc.
A typical feature of spinal canal stenosis is that pain and weakness in the legs increase while walking and ease when the person stops, bends forwards or sits down.
Spondylolisthesis occurs when one vertebra slips forwards in relation to the vertebra below it. It most commonly affects the lowest lumbar vertebrae, precisely where the roots of the sciatic nerve leave the spine. If the openings through which the nerve roots exit the spinal canal become narrower, sciatica can develop and is often aggravated by standing or physical strain.
Restricted movement or inflammation in the sacroiliac joint between the sacrum and the ilium frequently causes pseudoradicular pain in the buttock and thigh. You can learn more in our article on SIJ pain. Osteoarthritis of the small vertebral joints, known as the facet joints, can produce similar symptoms. Further information is available on our osteoarthritis treatment page.
The pear-shaped piriformis muscle lies deep in the buttock. It runs from the sacrum to the greater trochanter of the thigh bone and rotates the leg outwards. The sciatic nerve usually passes directly beneath it and, in some people, even runs through the muscle. If the muscle is tense, overloaded or thickened, it can compress the nerve and cause sciatic pain.
A deep pain in the buttock that radiates down the back of the thigh is typical. It often becomes worse after prolonged sitting, when climbing stairs or when crossing the legs. Lower back pain, by contrast, is usually absent.
Piriformis syndrome may be promoted by a fall onto the buttock, repetitive strain from running or a difference in leg length that places greater strain on one side.
Several of these factors may be present at the same time, for example osteoarthritis of the facet joints combined with spinal canal stenosis. A careful examination is therefore necessary to establish which cause is primarily responsible in each individual case.
When is sciatica an emergency?
Go to hospital immediately if you notice numbness around the genitals, buttocks or anus. Doctors refer to this as saddle anaesthesia because the affected area corresponds to the part of the body that rests on a saddle. The same applies if you suddenly develop problems passing urine or controlling your bladder or bowels. Even one of these warning signs may indicate cauda equina syndrome, in which several nerve roots are compressed at the same time.
If sciatica is accompanied by signs of paralysis, arrange an orthopaedic assessment promptly. This indicates that the compressed nerve root is already losing function. If the front of your foot catches on the ground or you can no longer walk on your heels, this suggests foot drop, which is usually caused by pressure on the L5 nerve root. You should also seek prompt medical assessment if the symptoms begin after a fall or are accompanied by a fever. In these situations, a vertebral fracture or inflammation of the spine may be irritating the nerve.
How is sciatica diagnosed?
Your description provides the first clues: When did the pain start, where does it travel, and what makes it better or worse? During the physical examination, we test the patellar and Achilles tendon reflexes, the strength of individual key muscles, for example by asking you to walk on your toes and heels, and sensation in the lower leg and foot. During the straight leg raise test, also known as the Lasègue test, we lift the straightened leg while you are lying down. If this causes pain to travel below the knee, it suggests an irritated nerve root. Specific provocation tests help us determine whether the sacroiliac joint is involved.
It is also important to consider other conditions that can mimic sciatica. Osteoarthritis of the hip often causes pain that radiates into the groin and thigh. Circulatory problems in the legs, like spinal canal stenosis, may force a person to stop while walking. Polyneuropathy, for example due to diabetes, usually causes tingling and numbness in both feet.
Magnetic resonance imaging (MRI) is not necessary in every case. Herniated discs and degenerative changes can also be seen on scans of many people who have no symptoms at all. During the first few weeks, the imaging result usually does not change the treatment. An MRI scan is appropriate if the nerve is already losing function, for example if there is paralysis or pronounced numbness, if one of the warning signs described above is present, or if the pain persists for several weeks despite consistent treatment.
How can sciatica be treated?
The appropriate treatment depends on the cause. At our private practice for orthopaedics and traumatology in Frankfurt, we offer a range of treatments that can be combined according to the individual findings:
Under CT or MRI guidance, we deliver an anti-inflammatory medication to the affected nerve root (periradicular therapy) or into the space surrounding the spinal membranes (epidural injection).
Injections into the facet joints or sacroiliac joint and neural therapy can reduce pain and inflammation. If the sacroiliac joint is restricted, chiropractic treatment can help to restore mobility.
Traction treatment and acupuncture can support recovery and help to maintain the result.
Bed rest tends to delay improvement, whereas appropriate movement promotes recovery. During physiotherapy, you learn exercises that strengthen the core and back muscles and reduce the long-term strain on the spine. Once the acute pain subsides, it is usually possible to return to sport. Swimming, cycling and walking are suitable activities, while sports involving jumps or abrupt twisting movements should initially be paused. We will be happy to discuss how to rebuild your training safely as part of our sports medicine service.
We review how your symptoms are progressing and adjust the treatment when necessary.
Sciatica treatment: your experienced orthopaedic team in Frankfurt
At our private practice for orthopaedics and traumatology at Hochstrasse 31 in Frankfurt, we determine what is causing your sciatica. As part of our spine treatment programme, we recommend a treatment plan tailored to your individual situation.
You can arrange an appointment online via Doctolib or by calling 069 26 95 28 00.
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