Sciatica pain is associated with a disc disorder in 85% of cases. Sciatica is shown to resolve without treatments in the majority of cases. Spontaneous regression of the intervertebral disc herniation occurs where the herniation loses its volume partly or totally without surgical interventions. It has estimated that only 5 to 20% of patients with symptomatic intervertebral disc herniation require surgery. Most trials comparing surgical trials and conservative treatments of sciatica due to intervertebral disc herniation favor surgery, because it results in earlier relief of pain. However, one year after surgery, there were only a few differences in pain and disability between surgery and conservative treatment groups. It has shown that the number of surgeries (discectomies) decreased among patients with sciatica when treated by using a mechanical diagnosis and therapy approach (MDT) also called the McKenzie method. In addition, by using the MDT method it has also been shown that sciatica patient who were clinically classified as "centralizers" had good to excellent non-surgical outcomes and many of them avoided surgery, whereas non-centralizing pain has shown to predict worse treatment outcomes, chronic low back disorder and disability. Further, patients who do not have centralization will be 6 times more likely to undergo surgery.The primary aim of this multicenter randomized clinical trial is to find out how many patients with sciatica due to intervertebral disc herniation with radicular symptoms for at least 6 weeks, and who are on the waiting list for surgery, avoid surgery by treatment using the McKenzie method compared to advice to stay active. Secondary aims are to compare the patients' self-reported outcomes such as low back and leg pain intensity, disability, work ability, sick-leave days, fear avoidance beliefs, kinesiophobia, depression and quality of life. The outcomes are measured at baseline, two and three months in the non-surgical patients. In addition, in the patients who have surgery the outcomes are measured at baseline and the day before and one month after surgery. Follow-up measurements are at 12 and 24 months

One hundred seventy two (N=172) patients with sciatica for at least six weeks with radicular pain below the knee will be involved this study. The patients with non-urgent referrals due to sciatica symptoms will be directed to specialized medical care hospitals (the district central hospitals of Central Finland and South Ostrobothnia and the University hospital of Kuopio, Finland) to the physiatrists and orthopedic outpatient clinics for further investigations for possible surgery. The patient will be seen for a doctor's examination within a week. If the clinical examination reveals that a patient needs spinal disc herniation surgery, and the patient is willing to undergo surgery, they will be referred for X-ray imaging if it has not already been done in basic health care, in accordance with the regular treatment procedure, and to an MRI scan.

While patients are waiting for their MRI scan, they will undergo a clinical McKenzie-based mechanical assessment and be put into sub-groups of "centralizers"or "non-centralizers". These will be randomly assigned into a McKenzie group and into an advice to stay active group. Based on their MRI findings and clinical signs and symptoms they will be assigned to surgery or continue their non-surgical treatments. If the MRI scan does not reveal a spinal disc herniation finding that fulfills the criteria of the study, the patient is removed from the study in accordance with the selection criteria, regardless of whether they belong to the MDT or advice to stay active group, and their treatment will continue according to the hospital's normal procedures.

Inclusion Criteria: The participants are 18 - 60-year-old Finnish speaking sciatica patients for whom magnetic resonance imaging confirmed disc herniation compressing a nerve root canal, and who have related symptoms radiating to the lower limb +/- neurological disorders. Their sciatica has lasted at least 6 weeks.

Exclusion Criteria:

Pregnancy, previous surgery or treated by using MDT- method, fibromyalgia, signs of serious diseases or "red-flags" symptoms. Symptoms indicating the Cauda Equina Syndrome (CES) or lower limb palsy that hinders normal functioning, previous injury from a car accident or a high fall, or osteoporotic fractures for the elderly, cancer anamnesis, tumor, or inflammation, general symptoms such as fever, chills, or losing weight for an unknown reason, back problems complicated by other serious diseases such as polyneuropathy, neurological diseases, circulatory brain diseases, central spinal stenosis, myelopathy, syringomyelia, and long-term neuropathic pain not related to sciatica, unwillingness to undergo surgery.