Com­mon causes of low back pain include lum­bar strain, nerve irri­ta­tion, lum­bar radicu­lopa­thy, bony encroach­ment, and con­di­tions of the bone and joints. Each of these is reviewed below.

1. Lum­bar strain (acute, chronic)
   A lum­bar strain is a stretch­ing injury to the lig­a­ments, ten­dons, and/or mus­cles of the low back. The stretch­ing inci­dent results in micro­scopic tears of vary­ing degrees in these tis­sues. Lum­bar strain is con­sid­ered one of the most com­mon causes of low back pain. The injury can occur because of overuse, improper use, or trauma. Soft-tissue injury is com­monly clas­si­fied as “acute” if it has been present for days to weeks. If the strain lasts longer than three months, it is referred to as “chronic.”

   Lum­bar strain most often occurs in peo­ple in their for­ties, but it can hap­pen at any age. The con­di­tion is char­ac­ter­ized by local­ized dis­com­fort in the low back area with onset after an event that mechan­i­cally stressed the lum­bar tis­sues. The sever­ity of the injury ranges from mild to severe, depend­ing on the degree of strain and result­ing spasm of the mus­cles of the low back.

   The diag­no­sis of lum­bar strain is based on the his­tory of injury, the loca­tion of the pain, and exclu­sion of ner­vous sys­tem injury. Usu­ally, x-ray test­ing is only help­ful to exclude bone abnormalities.

   The treat­ment of lum­bar strain con­sists of rest­ing the back (to avoid re-injury), med­ica­tions to relieve pain and mus­cle spasm, local heat appli­ca­tions, mas­sage, and even­tual (after the acute episode resolves) recon­di­tion­ing exer­cises to strengthen the low back and abdom­i­nal mus­cles. Long peri­ods of inac­tiv­ity in bed are no longer pro­moted, as this treat­ment may actu­ally slow recov­ery. Spinal manip­u­la­tion for peri­ods of up to one month has been found help­ful in some patients that do not have signs of nerve irri­ta­tion. Future injury is avoided by using back-protection tech­niques dur­ing activ­i­ties and sup­port devices as needed at home or work.

2. Nerve irri­ta­tion
   The nerves of the lum­bar spine can be irri­tated by mechan­i­cal impinge­ment or dis­ease any where along their paths—from their roots at the spinal cord to the skin sur­face. These con­di­tions include lum­bar disc dis­ease (radicu­lopa­thy), bony encroach­ment, and inflam­ma­tion of the nerves caused by a viral infec­tion (shin­gles). See dis­cus­sions of these con­di­tions below.
3. Lum­bar radicu­lopa­thy
   Lum­bar radicu­lopa­thy is nerve irri­ta­tion that is caused by dam­age to the discs between the ver­te­brae. Dam­age to the disc occurs because of degen­er­a­tion (“wear and tear”) of the outer ring of the disc, trau­matic injury, or both. As a result, the cen­tral softer por­tion of the disc can rup­ture (her­ni­ate) through the outer ring of the disc and abut the spinal cord or its nerves as they exit the bony spinal col­umn. This rup­ture is what causes the com­monly rec­og­nized “sci­at­ica” pain that shoots down the leg. Sci­at­ica can be pre­ceded by a his­tory of local­ized low-back aching or it can fol­low a “pop­ping” sen­sa­tion and be accom­pa­nied by numb­ness and tin­gling. The pain com­monly increases with move­ments at the waist and can increase with cough­ing or sneez­ing. In more severe instances, sci­at­ica can be accom­pa­nied by incon­ti­nence of the blad­der and/or bow­els.
   Lum­bar radicu­lopa­thy is sus­pected based on the above symp­toms. Increased radi­at­ing pain when the lower extrem­ity is lifted sup­ports the diag­no­sis. Nerve test­ing (EMG/electromyogram and NCV/nerve con­duc­tion veloc­ity) of the lower extrem­i­ties can be used to detect nerve irri­ta­tion. The actual disc her­ni­a­tion can be detected with radi­ol­ogy test­ing, such as CAT or MRI scan­ning.
   Treat­ment of lum­bar radicu­lopa­thy ranges from med­ical man­age­ment to surgery. Med­ical man­age­ment includes patient edu­ca­tion, med­ica­tions to relieve pain and mus­cles spasm, cor­ti­sone injec­tion around the spinal cord (epidural injec­tion), phys­i­cal ther­apy (heat, mas­sage, ultra­sound, elec­tri­cal stim­u­la­tion), and rest (not strict bed rest, but avoid­ing re-injury). With unre­lent­ing pain, severe impair­ment of func­tion, or incon­ti­nence (which can indi­cate spinal cord irri­ta­tion), surgery may be nec­es­sary. The oper­a­tion per­formed depends on the over­all sta­tus of the spine, and the age and health of the patient. Pro­ce­dures include removal of the her­ni­ated disc with lamino­tomy (a small hole in the bone of the lum­bar spine sur­round­ing the spinal cord), laminec­tomy (removal of the bony wall), by nee­dle tech­nique (per­cu­ta­neous dis­cec­tomy), disc-dissolving pro­ce­dures (chemonu­cle­ol­y­sis), and others.

Pic­ture of her­ni­ated disc between L4 and L5

Cross-section pic­ture of her­ni­ated disc between L4 and L5

1. Bony encroach­ment
   Any con­di­tion that results in move­ment or growth of the ver­te­brae of the lum­bar spine can limit the space (encroach­ment) for the adja­cent spinal cord and nerves. Causes of bony encroach­ment of the spinal nerves include foram­i­nal nar­row­ing (nar­row­ing of the por­tal through which the spinal nerve passes from the spinal col­umn, out of the spinal canal to the body), spondy­lolis­the­sis (slip­page of one ver­te­bra rel­a­tive to another), and spinal steno­sis (com­pres­sion of the nerve roots or spinal cord by bony spurs or other soft tis­sues in the spinal canal). Spinal-nerve com­pres­sion in these con­di­tions can lead to sci­at­ica pain that radi­ates down the lower extrem­i­ties. Spinal steno­sis can cause lower-extremity pains that worsen with walk­ing and are relieved by rest­ing (mim­ic­k­ing poor cir­cu­la­tion). Treat­ment of these afflic­tions varies, depend­ing on their sever­ity, and range from rest to sur­gi­cal decom­pres­sion by remov­ing the bone that is com­press­ing the ner­vous tissue.
2. Bone and joint con­di­tions
   Bone and joint con­di­tions that lead to low back pain include those exist­ing from birth (con­gen­i­tal), those that result from wear and tear (degen­er­a­tive) or injury, and those that are from inflam­ma­tion of the joints (arthritis).
   Con­gen­i­tal bone con­di­tions—Con­gen­i­tal causes (exist­ing from birth) of low back pain include sco­l­io­sis and spina bifida. Sco­l­io­sis is a side­ways (lat­eral) cur­va­ture of the spine that can be caused when one lower extrem­ity is shorter than the other (func­tional sco­l­io­sis) or because of an abnor­mal design of the spine (struc­tural sco­l­io­sis). Chil­dren who are sig­nif­i­cantly affected by struc­tural sco­l­io­sis may require treat­ment with brac­ing and/or surgery to the spine. Adults infre­quently are treated sur­gi­cally but often ben­e­fit by sup­port bracing.

   Spina bifida is a birth defect in the bony ver­te­bral arch over the spinal canal, often with absence of the spin­ous process. This birth defect most com­monly affects the low­est lum­bar ver­te­bra and the top of the sacrum. Occa­sion­ally, there are abnor­mal tufts of hair on the skin of the involved area. Spina bifida can be a minor bony abnor­mal­ity with­out symp­toms. How­ever, the con­di­tion can also be accom­pa­nied by seri­ous ner­vous abnor­mal­i­ties of the lower extremities.

   Degen­er­a­tive bone and joint con­di­tions—As we age, the water and pro­tein con­tent of the body’s car­ti­lage changes. This change results in weaker, thin­ner, and more frag­ile car­ti­lage. Because both the discs and the joints that stack the ver­te­brae (facet joints) are partly com­posed of car­ti­lage, these areas are sub­ject to wear and tear over time (degen­er­a­tive changes). Degen­er­a­tion of the disc is called spondy­lo­sis. Spondy­lo­sis can be noted on x-rays of the spine as a nar­row­ing of the nor­mal “disc space” between the ver­te­brae. It is the dete­ri­o­ra­tion of the disc tis­sue that pre­dis­poses the disc to her­ni­a­tion and local­ized lum­bar pain (“lum­bago”) in older patients. Degen­er­a­tive arthri­tis (osteoarthri­tis) of the facet joints is also a cause of local­ized lum­bar pain that can be detected with plain x-ray test­ing. These causes of degen­er­a­tive back pain are usu­ally treated con­ser­v­a­tively with inter­mit­tent heat, rest, reha­bil­i­ta­tive exer­cises, and med­ica­tions to relieve pain, mus­cle spasm, and inflammation.

   Injury to the bones and joints—Frac­tures (break­age of bone) of the lum­bar spine and sacrum bone most com­monly affect elderly peo­ple with osteo­poro­sis, espe­cially those who have taken long-term cor­ti­sone med­ica­tion. For these indi­vid­u­als, occa­sion­ally even min­i­mal stresses on the spine (such as bend­ing to tie shoes) can lead to bone frac­ture. In this set­ting, the ver­te­bra can col­lapse (ver­te­bral com­pres­sion frac­ture). The frac­ture causes an imme­di­ate onset of severe local­ized pain that can radi­ate around the waist in a band-like fash­ion and is made intensely worse with body motions. This pain gen­er­ally does not radi­ate down the lower extrem­i­ties. Ver­te­bral frac­tures in younger patients occur only after severe trauma, such as from motor-vehicle acci­dents or a con­vul­sive seizure.In both younger and older patients, ver­te­bral frac­tures take weeks to heal with rest and pain reliev­ers. Com­pres­sion frac­tures of ver­te­brae asso­ci­ated with osteo­poro­sis can also be treated with a pro­ce­dure called ver­te­bro­plasty, which can help to reduce pain. In this pro­ce­dure, a bal­loon is inflated in the com­pressed ver­te­bra, often return­ing some of its lost height. Sub­se­quently, a “cement” (methymethacry­late) is injected into the bal­loon and remains to retain the structure.

   Arthri­tis—The spondy­loarthropathies are inflam­ma­tory types of arthri­tis that can affect the lower back and sacroil­iac joints. Exam­ples of spondy­loarthropathies include reac­tive arthri­tis (Reiter’s dis­ease), anky­los­ing spondyli­tis, pso­ri­atic arthri­tis, and the arthri­tis of inflam­ma­tory bowel dis­ease. Each of these dis­eases can lead to low back pain and stiff­ness, which is typ­i­cally worse in the morn­ing. These con­di­tions usu­ally begin in the sec­ond and third decades of life. They are treated with med­ica­tions directed toward decreas­ing the inflam­ma­tion. Newer bio­logic med­ica­tions have been greatly suc­cess­ful in both qui­et­ing the dis­ease and stop­ping the progression.

What are other causes of low back pain?

Other causes of low back pain include kid­ney prob­lems, preg­nancy, ovary prob­lems, and tumors.

1. Kid­ney prob­lems: Kid­ney infec­tions, stones, and trau­matic bleed­ing of the kid­ney (hematoma) are fre­quently asso­ci­ated with low back pain. Diag­no­sis can involve urine analy­sis, sound­wave tests, or radi­o­log­i­cal scan­ning of the abdomen.
2. Preg­nancy: Preg­nancy com­monly leads to low back pain by mechan­i­cally stress­ing the lum­bar spine (chang­ing the nor­mal lum­bar cur­va­ture) and by the posi­tion­ing of the baby inside of the abdomen. Addi­tion­ally, the effects of the female hor­mone estro­gen and the ligament-loosening hor­mone relaxin may con­tribute to loos­en­ing of the lig­a­ments and struc­tures of the back. Pelvic-tilt exer­cises are often rec­om­mended for this pain. Women are also rec­om­mended to main­tain phys­i­cal con­di­tion­ing dur­ing preg­nancy accord­ing to their doc­tors’ advice.
3. Ovary prob­lems: Ovar­ian cysts, uter­ine fibroids, and endometrio­sis not infre­quently cause low back pain. Pre­cise diag­no­sis can require gyne­co­logic exam­i­na­tion and testing.
4. Tumors: Low back pain can be caused by tumors, either benign or malig­nant, that orig­i­nate in the bone of the spine or pelvis and spinal cord (pri­mary tumors) and those which orig­i­nate else­where and spread to these areas (metas­ta­size). Symp­toms range from local­ized pain to radi­at­ing severe pain and loss of nerve and mus­cle func­tion (even incon­ti­nence of urine and stool) depend­ing on whether or not the tumors affect the ner­vous tis­sue. Tumors of these areas are detected using radi­o­log­i­cal tests, such as plain x-rays, nuclear bone scan­ning, and CAT and MRI scanning.

What are uncom­mon causes of low back pain?

Uncom­mon causes of low back pain include Paget’s dis­ease of bone, bleed­ing or infec­tion in the pelvis, infec­tion of the car­ti­lage and/or bone of the spine, aneurysm of the aorta, and shingles.

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. Treat­ment options include aspirin, other anti-inflammatory med­i­cines, pain med­ica­tions, and med­ica­tions that slow the rate of bone turnover, such as cal­ci­tonin (Cal­ci­mar, Mia­cal­cin), etidronate (Didronel), alen­dronate (Fos­amax), rise­dronate (Actonel), and pamidronate (Aredia).
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 (osteomyelitis) 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 and Mycobac­terium tuber­cu­lo­sis (TB 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: 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 chick­en­pox 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). Treat­ment can involve symp­to­matic relief with lotions, such as calamine, or med­ica­tions, such as acy­clovir (Zovi­rax) for the infec­tion and pre­ga­balin (Lyrica) for the pain.