Muscle:Iliocostalis Lumborum

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Iliocostalis lumborum is the most laterally placed of the superficial (erector spinae) paraspinal muscles in the lumbar region and one of the two muscles of the erector spinae group most likely to develop active trigger points (TrPs). Its TrPs refer pain strongly downward, concentrating on the mid-buttock — a remote and frequently overlooked source of unilateral posterior hip pain. At the upper lumbar level, TrPs also refer pain to the sacroiliac region and the flank, and experimental injection at the L1 level produced pain characteristic of renal colic. Iliocostalis lumborum TrPs are closely associated with pelvic obliquity and sacroiliac dysfunction.

Anatomy

The iliocostalis lumborum extends above from the angles of the lowest six ribs and below to the sacrum. It is the most laterally placed of the lumbar paraspinal muscles, forming the lateral column of the erector spinae group.

At lower thoracic levels, the iliocostalis lumborum overlaps in location with the iliocostalis thoracis, since the two iliocostalis muscles overlap in this region. The fasciculi from the lowest two ribs lie nearly vertically and are parallel and adjacent to those of the quadratus lumborum. Caudally, the iliocostalis lumborum blends with the spinalis muscles.

The paraspinal musculature as a whole is simplified by thinking of it as two layers: a superficial layer of long-fibred longitudinal extensors (erector spinae), and a deep layer of shorter, more diagonal extensor rotators (transversospinal muscles).

Primary function: Acting unilaterally, the iliocostalis lumborum produces lateral flexion and rotation to the same side. Acting bilaterally, it extends the spine. Acts eccentrically ("paying out") to control spinal flexion. The bilateral iliocostalis lumborum usually becomes active at the end of inhalation and also during exhalation when the ventilation rate is close to its maximum — it can depress the lower ribs.

Innervation: Lateral branches of the dorsal primary divisions of the corresponding spinal nerves.

Referred Pain Patterns

Upper lumbar level (approximately L1): TrPs at this level refer pain strongly downward, concentrating on the mid-buttock. This is a frequent and easily overlooked source of unilateral posterior hip pain. Pain is also referred to the sacroiliac region and flank. Experimental injection of hypertonic saline along the edge of the interspinous ligament at the L1 level referred pain characteristic of renal colic to the loin, inguinal, and scrotal areas, causing retraction of the testicle. At the T9 level, posteriorly injected hypertonic saline caused palpable rigidity and deep tenderness of the lowest part of the abdominal wall.

Lower thoracic overlap zone: At lower thoracic levels where the iliocostalis lumborum overlaps with the iliocostalis thoracis, pain may be referred both caudally and cephalad. A quadriparetic patient had pain and tenderness in the right lower quadrant, right flank, and right subcostal area with a right subcostal TrP in the iliocostalis lumborum — the pain pattern was more like that of a low iliocostalis thoracis TrP than a high iliocostalis lumborum TrP, suggesting that the spinal cord may not make a clear distinction at the transition zone.

Pain from these muscles is a common muscular source of "lumbago." The patient usually draws an up-and-down pattern to represent pain referred from iliocostalis TrPs — in contrast to the crosswise pattern used to demonstrate pain from TrPs in the lower rectus abdominis in the same region.

Activation and Perpetuating Factors

  • Sudden overload: A quick awkward movement combining bending and twisting of the back, especially when the muscles are fatigued or chilled, is likely to activate TrPs even though no additional loading (lifting) is involved. This may be caused by disproportionate loading of one group of muscle fibres as the result of poor coordination
  • Sustained overload: Sustained contraction in the stooped posture, or when the back muscles are maintained in a fully shortened (hyperlordotic) position
  • Repetitive microtrauma: Sustained or repeated muscular contraction over a period of time
  • Structural asymmetries: Lower limb-length inequality, disturbance of pelvic symmetry — including a small hemipelvis when sitting and a short leg when standing — impose persistent muscle strain that perpetuates TrPs and must be corrected for lasting relief (see Corrective Actions)
  • Small hemipelvis / pelvic tilt: Pelvic tilt may also be produced unwittingly by sitting on a wallet in the back pocket ("back-pocket sciatica"), by sitting regularly in a tilted office chair, or on a piano bench placed on a slanted stage
  • Prolonged immobility: Sitting for hours with the seat belt fastened in aircraft or automobile; EMG studies showed that typists who remained immobile in their optimally relaxed position developed muscular activity in about 30 minutes
  • Whiplash: The whiplash type of accident causing sudden acceleration or deceleration rapidly stretches protectively stiffened spinal muscles, likely activating TrPs
  • Sacroiliac dysfunction: Iliocostalis lumborum TrPs are closely associated with pelvic obliquity secondary to tension applied to the muscle's insertional aponeurosis onto the sacral base — this can present as a sacroiliac dysfunction demonstrated by a positive seated-flexion test. Note that the side of the positive seated-flexion test is not the side of the sacroiliac dysfunction
  • Satellite TrP relationship: The iliocostalis frequently has a TrP that is a satellite induced by a key TrP in the latissimus dorsi, which must be treated first for full recovery

Clinical Examination

Superficial Paraspinal Examination

Palpation of superficial paraspinals is less effective with the patient standing because of postural muscle tension and protective splinting by normal muscles. The examiner must obtain relaxation of the patient's back muscles so that abnormally taut muscle fibres are distinguishable from adjacent normal, slackened fibres.

Seated position: When the seated patient leans forward, dangles the arm between the legs, and relaxes, an involved lumbar iliocostalis on one side is evident and feels like a hard rope.

Sidelying position (optimal): The patient lies on the uninvolved side with a pillow under the side of the abdomen for semiprone support. The full prone position often strains the neck and tends to over-slacken the paraspinal muscles for examination. The back muscles must have an intermediate degree of stretch so that taut bands containing TrPs can be distinguished from adjacent normal, slackened muscle fibres. The degree of stretch is regulated by bringing the patient's knees toward the chest just far enough to take up the slack in the long erector spinae. Flat palpation then elicits spot tenderness (of a palpable nodule in a taut band) and often elicits patient-recognised referred pain.

Skin changes: The skin overlying involved lumbar paraspinal muscles often exhibits superficial tenderness and resistance to skin rolling (panniculosis) or trophedema, which disappears after therapeutic skin rolling and inactivation of the underlying myofascial TrPs.

General Signs

Local areas of reduced skin resistance to direct current are characteristic of the musculoskeletal and myofascial symptoms of backache with limitation of spinal motion.

After the erector spinae on the painful side have been passively stretched during vapocooling and the muscles on that side have relaxed, mirror-image pain and muscular tension may appear, so that the opposite lumbar iliocostalis now stands out and feels tense. The two sides frequently function together as a unit and are likely to develop TrPs together.

Sacroiliac Dysfunction Screening

The seated-flexion test is positive on the side of the sacroiliac dysfunction. Iliocostalis lumborum TrPs at the upper lumbar level are closely associated with sacroiliac dysfunction secondary to tension in the muscle's insertional aponeurosis onto the sacral base. The side of the positive seated-flexion test indicates the side of the dysfunction.

Differential Diagnosis

Condition Distinguishing features
Renal colic Upper lumbar iliocostalis lumborum TrPs refer pain to the loin, inguinal, and scrotal areas, mimicking renal colic; urinalysis and imaging differentiate; TrP injection relieves the referred pain
Sacroiliac dysfunction Iliocostalis lumborum TrPs are closely associated with sacroiliac dysfunction via tension on the insertional aponeurosis; seated-flexion test identifies the side of dysfunction; treat both the TrPs and any articular dysfunction
Posterior hip pain / trochanteric bursitis Upper lumbar iliocostalis lumborum TrP referring strongly to the mid-buttock is a frequently overlooked source of posterior hip pain; no local tenderness over the greater trochanter in pure TrP referral; TrP injection resolves the buttock pain
Radiculopathy Paraspinal TrPs alone do not produce neurological deficits (decreased tendon reflexes, impaired cutaneous sensation, motor weakness with atrophy); however, when active back muscle TrPs induce satellite TrPs in the gluteal muscles, the latter TrPs often refer myofascial pain down the lateral or posterior thigh, sometimes extending to the foot, mimicking radiculopathy
Iliolumbar syndrome Pain localised at the posterior portion of one iliac crest is frequently relieved by injections of a local anaesthetic penetrating the iliolumbar ligament, the quadratus lumborum muscle, or both; some cases may have fascial TrPs in the ligaments
Fibromyalgia Any patient with chronic low back pain and additional widespread pain should be examined for fibromyalgia; patients with fibromyalgia frequently also have myofascial TrPs and each diagnosis requires its own therapeutic approach
Fat lobules Fibrolipomatous nodules at T12–L2 levels referred pain to back, abdomen, groin, and testicle; temporarily relieved by local injection and permanently relieved by surgical excision; subcutaneous location distinguishes from deep muscle TrPs

Treatment

Trigger Point Release — Spray and Stretch

Either of two seated stretch positions can be used:

Less strenuous seated position — chiefly stretches the long thoracic paraspinal muscles:

  1. Patient sits in a chair with feet placed comfortably on the floor and legs apart
  2. Patient leans forward, lets the head hang forward, and lets the arms drop between the knees
  3. After a few initial sweeps of vapocoolant spray, the operator gradually increases pressure on the upper back to guide the patient's movement as the vapocoolant spray is directed over the paraspinal muscles bilaterally in long downward parallel sweeps
  4. At the same time, to hyperflex the thoracic spine, the patient is told to take a deep breath, to exhale fully, and to curl or "Hump the back!" (the wrong instruction, "Arch your back!", causes the patient to extend rather than flex the spine)
  5. Vapocooling is followed promptly by application of moist heat to rewarm the skin, then by active range of motion

More strenuous long-sitting position — strongly stretches the thoracic and lumbar paraspinal, lumbosacral, gluteal and hamstring muscles:

  1. Patient assumes the long-sitting position on a flat surface with the hips flexed and the knees straight
  2. The paraspinal and gluteal muscles are then sprayed in parallel downward sweeps, as in the seated position, but the sweeps continue over the buttocks
  3. This position places a strong stretch on the gluteus maximus and hamstring muscles, which, if tight, should first be released by stretch and spray during straight-leg raising before the full range of hip flexion is attempted

PIR (postisometric relaxation): In the supine position, with the hips and knees flexed and held by the hands, the patient can augment the low back stretch using PIR. The patient presses the buttocks downward against the bed (contracting the lumbar extensors) and then relaxes, pulling the thighs up toward the chest.

Trigger Point Pressure Release

The patient can apply self-release therapy to TrPs in the superficial back muscles by lying supine on a tennis ball, either on the floor or on a bed with a large thin book placed under the ball. The patient moves around until the ball presses directly on the sensitive TrP; controlled body weight is used to apply gradually increasing pressure for a minute or more, until the spot loses its deep tenderness. Moist heat applied afterward and full range of motion enhance the beneficial effects.

Trigger Point Injection

The longissimus and iliocostalis TrPs are clearly palpable and readily located for injection in all but very obese patients. When injecting TrPs in the superficial group at the mid- to low-thoracic level, a TrP located more laterally in the iliocostalis refers pain upward toward the shoulder; one located more medially in the longissimus refers pain caudally — this difference in referral direction helps identify which muscle the needle is in.

When injecting the iliocostalis thoracis muscle, the needle must be directed tangent to, and not between, the ribs, to avoid pneumothorax.

Distinguishing central from attachment TrPs in the paraspinal muscles can be difficult even in the more superficial muscles. The presence of a tender nodule with a taut band extending in either direction is highly suggestive of a central TrP.

The TrP injection is followed at once by a repetition of stretch and spray, then by moist heat and active range of motion.

Corrective Actions

Trigger Point Pressure Release (Self-Treatment)

Self-application of TrP pressure release using a tennis ball (see Treatment above).

Correction of Structural Inadequacies

A functional scoliosis develops in order to compensate for lateral tilting of the pelvis caused by a short leg when standing, or by a small hemipelvis when sitting. Such body asymmetry imposes persistent muscle strain that perpetuates TrPs in the paraspinal and associated musculature, and must be corrected.

  • Limb-length inequality: A difference of as little as 0.3 cm (1/8 in) in a short person should be corrected. The correction must be worn whenever these patients are on their feet, including bedroom slippers. A difference of 0.5 cm (3/16 in) is often a significant source of muscle strain requiring correction. Correction is accomplished by inserting the correct thickness of firm felt inside the heel of the shoe of the short side, or permanently by building up the outside thickness of the shoe heel
  • Asymmetrical pelvis (small hemipelvis): Pelvic tilt is corrected by placing enough pages or sheets of paper under the ischial tuberosity on the shorter side to level the pelvis exactly when sitting on a flat hard surface

Modification of Activities

  • The patient must learn to pick up any low object by broadening the base of support, bending the knees while keeping the back upright — transferring the load from the back muscles to the hip and knee extensors
  • During lifting, a heavy object must be held close to the body with the pelvis "tucked in"
  • A particularly hazardous movement is a twisting turn while lifting or pulling. It is MUCH safer to rotate the body and face the load squarely, or to lift the load while facing it and then pivot with the feet to redirect where the load goes
  • Sit-to-stand technique: Move the hips forward to the front of the chair seat, turn the body and hips somewhat to the side, and place one foot beneath the front edge of the chair; hold the torso erect while the knees and hips are straightened. The reverse Stand-to-sit technique maintains the back in an erect position and transfers the load from paraspinal to hip and thigh muscles

Modification of Environment

  • The backrest of a chair should provide enough lumbar support to maintain the normal lumbar lordotic curve when the muscles relax
  • A bed that is too soft and sags in the middle aggravates tension in the back muscles — remedied by placing a plywood board between the mattress and the bed spring
  • When sleeping on the side rather than supine, a pillow placed under the uppermost knee prevents the rotary torsion of the lumbar spine that occurs when the knee drops forward onto the bed

Exercises

  • In-bathtub Stretch Exercise: Performed in comfortably warm water; the patient actively leans forward with the knees straight and assists dorsal relaxation by letting the head hang forward, then walks the fingers down the shins until a pull is felt on the stretched paraspinal muscles, then a little further to slight discomfort. After holding for several seconds, tautness usually slackens; the patient leans back, relaxes, breathes deeply with abdominal respiration, then leans forward to take another step of the fingers to "take up the slack." This slow, step-wise passive stretch helps recapture the lost range of motion of the long back muscles
  • Low-back Stretching Exercise: Supine; draw one knee to the chest with hands clasped around the thigh behind the knee (not the knee itself, to avoid forced knee flexion). Return that lower limb to the straight-leg starting position, then flex the other thigh to the chest. Finally, both legs are pulled to the chest
  • Abdominal strengthening: Strong abdominal muscles provide 30–50% additional weight-carrying support to the thoracolumbar spine; abdominal strengthening using Sit-back, Abdominal-curl, and Sit-up exercises should be performed slowly, not rapidly

Satellite Trigger Points

  • Iliocostalis thoracis — cephalad continuation; overlaps at the lower thoracic level; the two muscles function as a unit and frequently develop TrPs together
  • Longissimus thoracis — medial synergist; immediately adjacent; commonly co-active
  • Latissimus dorsi — a key TrP in the latissimus dorsi frequently activates the iliocostalis lumborum as a satellite; the latissimus must be treated first for full recovery
  • Quadratus lumborum — articular dysfunction of the thoracolumbar junction is often associated with active TrPs in the adjacent erector spinae, psoas, and quadratus lumborum; treating one often relieves TrPs in another
  • Gluteus medius / Gluteus minimus — satellite TrPs induced by key paraspinal TrPs; refer pain down the lateral or posterior thigh

References

  • Travell JG, Simons DG. Myofascial Pain and Dysfunction: The Trigger Point Manual, Volume 2: The Lower Extremities. Baltimore: Williams & Wilkins; 1992. Chapter 48.
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