1. Paget's disease of bone
Paget's disease of the bone is a condition of unknown cause in which the bone formation is out of synchrony with normal bone remodeling. This condition results in abnormally weakened bone and deformity and can cause localized bone pain. Paget's disease is more common in people over the age of 50. Heredity (genetic background) and certain unusual virus infections have been suggested as causes. Thickening of involved bony areas of the lumbar spine can cause the radiating lower extremity pain of sciatica.
Paget's disease can be diagnosed on plain x-rays. However, a bone biopsy is occasionally necessary to ensure the accuracy of the diagnosis. Bone scanning is helpful to determine the extent of the disease, which can involve more than one bone area. A blood test, alkaline phosphatase, is useful for diagnosis and monitoring response to therapy.
2. Bleeding or infection in the pelvis
Bleeding in the pelvis is rare without significant trauma and is usually seen in patients who are taking blood-thinning medications, such as warfarin (Coumadin). In these patients, a rapid-onset sciatica pain can be a sign of bleeding in the back of the pelvis and abdomen that is compressing the spinal nerves as they exit to the lower extremities. Infection of the pelvis is infrequent but can be a complication of conditions such as diverticulosis, Crohn’s disease, ulcerative colitis, infection of the tubes or uterus, and even appendicitis. This is a serious complication of these conditions and is often associated with fever, lowering of blood pressure, and a life-threatening state.
3. Infection of the cartilage and/or bone of the spine
Infection of the discs (septic discitis) and bone or osteomylitis is extremely rare. These conditions lead to localized pain associated with fever. The bacteria found when these tissues are tested with laboratory cultures include staphylococcus aureus andmycobacterium tuberculisis bacteria). TB infection in the spine is called pott’s disease. These are each very serious conditions requiring long courses of antibiotics. The sacroiliac joints rarely become infected with bacteria. Brucellosis is a bacterial infection that can involve the sacroiliac joints and is usually transmitted in goat's milk.
4. Aneurysm of the aorta
In the elderly, atherosclerosis can cause weakening of the wall of the large arterial blood vessel (aorta) in the abdomen. This weakening can lead to a bulging (aneurysm) of the aorta wall. While most aneurysms cause no symptoms, some cause a pulsating low back pain. Aneurysms of certain size, especially when enlarging over time, can require surgical repair with a grafting procedure to repair the abnormal portion of the artery.
5. Shingles (Herpes zoster)
Is an acute infection of the nerves that supply sensation to the skin, generally at one or several spinal levels and on one side of the body (right or left). Patients with shingles usually have had chicken pox earlier in life. The Herpes virus that causes chickenpox is believed to exist in a dormant state within the spinal nerve roots long after the chickenpox resolves. In people with shingles, this virus reactivates to cause infection along the sensory nerve, leading to nerve pain and usually an outbreak of shingles (tiny blisters on the same side of the body and at the same nerve level). The back pain in patients with shingles of the lumbar area can precede the skin rash by days. Successive crops of tiny blisters can appear for several days and clear with crusty inflammation in one to two weeks. Patients occasionally are left with a more chronic nerve pain (postherpetic neuralgia).
Research Source here.
Research Source here.