Introduction

Use of cortisone injections in the treatment of muscle and joint inflammatory reactions is becoming increasingly popular. First popularized by Janet Travell, MD, muscle injections are a remarkably effective adjunct to pharmacologic and physical therapies and are safe and easy to perform. Joint injections, while technically more difficult to perform, also can be of great benefit in the patient's recovery. The purpose of this article is to introduce the basic principles of muscle and joint injections.

Mechanism of Inflammation 

Inflammation is one of the body's first reactions to injury. Release of damaged cells and tissue debris occurs upon injury. These expelled particles act as antigens to stimulate a nonspecific immune response and to cause the proliferation of leukocytes. Local blood flow increases to transport the polymorphonuclear leukocytes, macrophages, and plasma proteins to the injured area. A redistribution of arteriolar flow produces stasis and hypoxia at the injury site. The resulting infiltration of tissues by the leukocytes, plasma proteins, and fluid causes the redness, swelling, and pain that are characteristic of inflammation.

Inflammatory muscle and joint injuries are associated with many causes, including the following:

  • Muscle strains
  • Trauma
  • Polyarthritis
  • Connective tissue disease
  • Degenerative joint disease (DJD)
  • Tendinitis
  • Bursitis
  • Arthritis
  • Neoplasm
  • Inherited congenital disorders
  • Miscellaneous systemic diseases

Initially, the inflammatory reaction serves several important purposes. The influx of leukocytes facilitates the process of phagocytosis and the removal of damaged cells and other particulate matter. Pain and tenderness remind the patient to protect the injured area; however, the inflammatory reaction eventually becomes counterproductive. The extravascular pressure exerted by the edema may retard blood flow into the area and delay healing. Sometimes, the debris coagulates and forms hard masses, scarring, and/or trigger points in the muscle or joint, preventing normal function from returning

Actions of Corticosteroids

The mechanism of corticosteroid action includes a reduction of the inflammatory reaction by limiting the capillary dilatation and permeability of the vascular structures. These compounds restrict the accumulation of polymorphonuclear leukocytes and macrophages and reduce the release of vasoactive kinins. They also inhibit the release of destructive enzymes that attack the injury debris and destroy normal tissue indiscriminately.

Additionally, new research suggests that corticosteroids may inhibit the release of arachidonic acid from phospholipids, thereby reducing the formation of prostaglandins, which contribute to the inflammatory process. Finally, the clinician should appreciate the importance of introducing a needle into the injured area. The needle itself may provide drainage and a release of pressure, and it may also mechanically disrupt the scar tissue in the muscle.

Evaluation of the Patient

As with the treatment of any disorder, a carefully taken patient history and a carefully made physical examination are of paramount importance. Sharp, severe, intense pain suggests the presence of a more acute, traumatic reaction with marked inflammation. Dull, low-grade, chronic pain indicates the existence of a mild inflammatory reaction, a chronic overuse injury, or arthritis. Radiation of pain or additional neurologic symptoms (eg, tingling, burning, numbness) imply additional neurologic involvement. Medication history is important because discontinuation of anti-inflammatory medications often precipitates a reaction. Dietary changes also may precipitate reactions, such as an attack of gout.

The physical examination is performed to assess the location and severity of the reaction. Determination of whether the inflammation is in the muscle, tendon, or joint is of paramount importance. Trigger points in muscles can be easily identified if the clinician uses the appropriate palpation skills. Many clinicians ask their patients to identify the site of greatest discomfort. Patients often know exactly where the source of their pain is, having spent hours localizing it.

Radiographic studies may or may not be beneficial, because it takes a significant amount of effusion for the injury to appear on a routine radiograph. Usually, clinical symptoms are present and treatable long before a radiographic abnormality may be identified. On the other hand, radiographs are important in evaluating for fracture or determining acuity.

If joint and cartilage damage exists, the clinician knows that a long-standing process is involved. Electromyograms (EMGs) are extremely beneficial in determining whether there is a significant neurologic component to the patient's symptoms. This determination is important in targeting injection sites. Blood work can include blood counts and chemistry series. An elevated leukocyte or white blood cell count may indicate infection. An elevated erythrocyte sedimentation rate suggests that a significant myopathic or arthritic process has developed. Elevated rheumatoid factor implies chronic arthritic conditions, such as rheumatoid arthritis. Elevated uric acid levels are sometimes observed in patients with gout.

Treatment of the Patient

Treatment of the patient with an inflammatory condition involves a multidisciplinary approach. Anti-inflammatory medications (eg, aspirins, nonsteroidal anti-inflammatory drugs [NSAIDs], oral prednisone) are indicated in patients with acute and chronic inflammation. It should be remembered that a full therapeutic dose should initially be used. Many patients discontinue their medication after they have begun to feel better, leaving a low-lying inflammatory reaction. This author recommends first prescribing the NSAID for a 10- to 14-day period, with instructions to use up the medication as long as side effects do not develop. This should be followed up with an as-needed (prn) prescription.

Nonnarcotic pain medications, such as Elavil, may be beneficial in reducing the pain associated with inflammatory reactions. Although this is an area of some controversy, the use of narcotic medications is dependent on the severity of the pain, and these drugs should be used only for a limited duration.

In acute situations, rest, ice, heat, splinting, and bracing are important elements of care. With time, physical therapy, massage therapy, and general rehabilitation management become increasingly effective. While injection therapy is relatively safe, there are inherent dangers in any procedure where the skin is pierced, including infection, bleeding, joint ruptures, and perforation of vital structures. 

Indications for injection therapy may include any of the following inflammatory conditions:

  • Synovitis
  • Osteoarthritis
  • Bursitis
  • Gouty arthritis
  • Posttraumatic osteoarthritis (frozen shoulder syndrome)
  • Tendinitis
  • Rheumatoid arthritis
  • Muscle trigger points
  • Carpal tunnel and other entrapment syndromes                               
  • Fasciitis
  • Ganglion Cysts
  • Neuromas

Precautions for injection therapy include the following:

  • Charcot joint (neuropathic sensory loss)
  • Infection
  • Tumor
  • Neurogenic disease
  • Active infections (eg, tuberculosis)
  • Immune-suppressed hosts
  • Hypothyroidism
  • Bleeding dyscrasias
  • Uncontrolled diabetes
  • Joint prosthesis
  • Surrounding joint osteoporosis
  • Patellar or Achilles tendinopathies (possible tendon rupture)

The packing insert for corticosteroids lists additional significant precautions and contraindications. The physician should be familiar with all of these restrictions before considering injection therapy.

Potential local side effects of corticosteroid injections include infection, subcutaneous atrophy, skin depigmentation, and tendon rupture. These complications often result from poor technique, too large a dose, too frequent a dose, or a failure to mix and dissolve the medications properly.

Regarding injections for myofascial pain, some clinicians prefer to perform trigger point injections of corticosteroid, while others prefer to perform trigger point injections containing only local anesthetics or no medication at all ("dry needling").

See also

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