Foreign Body Synovitis

Foreign Body Synovitis

Foreign body synovitis is an inflammatory reaction of the synovium (from joint, bursa, or tendon sheath) attributable to the introduction of a foreign material. Most commonly, it results from a traumatic event, but it may also follow surgical introduction of foreign material.

Foreign body synovitis is an uncommon cause of joint or soft tissue pain encountered in clinical practice. Although foreign body synovitis can occur anywhere in the body when a foreign material is introduced into or near a joint, tendon sheath, or soft tissue surrounding a joint, the hand is most often affected.

When this occurs, a chronic, inflammatory monoarthritis or tenosynovitis results. Plant thorns, wood splinters, glass, and sea urchin spines are most commonly implicated.

After the initial injury, a patient with foreign body tenosynovitis may note localized pain in and around the joint. If the patient realizes a foreign body is present, he or she may try to remove it. If a portion of the foreign body is left behind, foreign body synovitis can occur.

After the acute injury, a period of quiescence may occur, lasting weeks to months. After this latent period, the patient begins to experience pain and loss of function in the area of the retained foreign body and an inflammatory monoarthritis or tenosynovitis may result.

What are the Symptoms of Foreign Body Synovitis

The diagnosis of foreign body synovitis is easy if the antecedent trauma is recognized. This is not usually the case, however. A patient with foreign body synovitis presents with a localized monoarthritis or synovitis without obvious cause.

The patient also may report myalgias or flu-like symptoms in some cases. Examination of other joints fails to reveal evidence of inflammatory arthritis, and the targeted history is negative. A high index of suspicion in any patient with monoarthritis combined with appropriate testing leads the clinician to a correct diagnosis.

What are the five activities that are risk factors for foreign body synovitis

Professional fishing, professional diving, marine recreational activities, farming, and gardening.

Differential Diagnosis

The recognition of the possibility of antecedent trauma with the introduction of a foreign body makes the diagnosis apparent. Foreign body synovitis must be distinguished from other causes of monoarthritis and synovitis. The below table lists common causes of monoarthritis.

The ultimate differential diagnosis usually requires a careful targeted history and physical examination combined with appropriate laboratory and radiographic testing.

Common Causes of Monoarthritis

Traumatic arthritis
Gonococcal arthritis
Charcot joint
Other crystal arthropathies
Villonodular synovitis
Foreign body synovitis

How is foreign body synovitis diagnosed?

The joints of the hands and knees are most commonly affected. There is sudden onset of pain at the site of injury, which may be forgotten by the patient or overlooked by the physician. The patient may be seen with acute synovitis several days after the injury, ranging from months to years later, with chronic synovitis (particularly of the knee).

Magnetic resonance imaging (MRI) and ultrasound imaging of the affected joint often reveal the offending foreign body. Vegetable matter such as plant thorns, wood, and glass are not radiopaque and do not show up on plain radiographs; failure to obtain MRI results in a missed diagnosis.

Sea urchin spines have a high calcium content and may appear on plain radiographs. Based on the patient’s clinical presentation, additional tests, including complete blood cell count, uric acid level, erythrocyte sedimentation rate, and antinuclear antibody testing, may be indicated. Electromyography is indicated if coexistent ulnar or carpal tunnel syndrome is suspected. Joint aspiration and synovial biopsy may be required to make the diagnosis of foreign body synovitis. Arthroscopy or arthrotomy may be the mechanism by which the diagnosis is finally made.

The inflammatory synovitis may be episodic. The ESR is usually normal, and synovial fluid is inflammatory with a predominance of neutrophils. Radiographs may show soft tissue swelling only and can be useful to detect radiodense particles (metal, fish bones, and sea urchin spines) but not wood, plastic, or plant thorns. Chronic changes of periarticular osteoporosis, osteolysis, osteosclerosis, and periosteal new bone formation can mimic osteomyelitis or bone tumors. Synovial biopsies show a nonspecific granulomatous synovitis that may be confused with sarcoidosis.

In the approximately two-thirds of patients with foreign body synovitis attributable to exogenous particles who develop a chronic or relapsing course, diagnosis and treatment usually necessitates excisional biopsy with synovectomy. Because of its resolution, ultrasound is better than computed tomography (CT) scanning and magnetic resonance imaging (MRI) in detecting particles that are too small or radiolucent to be seen with conventional radiography. Bacteriologic studies (including mycobacterial studies) and histopathologic examination of tissue are essential. Polarized microscopy is useful in detecting birefringent fragments of plant origin, sea urchin spines, and polymethylmethacrylate.

How is Foreign Body Synovitis treated?

Initial treatment of the pain and functional disability associated with foreign body synovitis should include a combination of nonsteroidal antiinflammatory drugs (NSAIDs) or cyclooxygenase-2 (COX-2) inhibitors and physical therapy. Local application of heat and cold also may be beneficial. For patients who do not respond to these treatment modalities, an injection into the affected area with a local anesthetic and steroid may be a reasonable next step.

The use of physical therapy, including gentle range-of-motion exercises, should be introduced several days after the patient undergoes this injection technique. Vigorous exercises should be avoided because they would exacerbate the patient’s symptoms. Surgical removal of the offending foreign body often is the only intervention that successfully treats foreign body synovitis.


The main complication associated with foreign body synovitis is the risk for permanent joint damage resulting from delayed diagnosis. Injection of the area of synovitis syndrome is a safe technique if the clinician is attentive to detail.

Inflamed tendons may rupture if directly injected, and needle position should be confirmed outside the tendon before injection to avoid this complication. Another complication of this injection technique is infection. This complication should be exceedingly rare if strict aseptic technique is followed.

Approximately 25% of patients report a transient increase in pain after this injection technique, and patients should be warned of this possibility.

Clinical Pearls

The diagnosis of foreign body synovitis is easy if the clinician thinks of it. By including foreign body synovitis in the differential diagnosis of patients with monoarthritis or tenosynovitis, the diagnosis is more easily recognized.

The early use of MRI and ultrasound imaging of the affected area also help increase the diagnostic accuracy of the clinician.


Sign up to receive the trending updates and tons of Health Tips

Join SeekhealthZ and never miss the latest health information