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Monarticular pain may originate from the joint itself or surrounding structures. There may be pain (arthralgia) or also inflammation (arthritis) with redness, warmth, and swelling. Pain may occur only with use, suggesting a mechanical problem (eg, osteoarthritis, tendinitis), or also at rest, suggesting inflammation (eg, crystal disease, septic arthritis). There may or may not be fluid within the joint (effusion). Prompt assessment is essential to exclude infection. It is important to remember that acute monarticular arthritis is sometimes the initial manifestation of some types of polyarticular arthritis (eg, psoriatic arthritis, RA).
Pathophysiology
Monarticular pain may originate
Intra-articular disorders may be inflammatory (eg, infectious, rheumatoid, crystal deposition arthritis) or noninflammatory (eg, osteoarthritis, internal derangement).
Periarticular disorders include bursitis and tendinitis.
Crystal-induced arthritis is usually caused by monosodium urate crystals (gout) or Ca pyrophosphate dihydrate crystals (pseudogout).
Etiology
At all ages, injury is the most common cause of acute monarticular joint pain; history of trauma is usually obvious.
Among young adults, the most common nontraumatic causes are the following:
Among older adults, the most common nontraumatic causes are the following:
The most dangerous cause at any age is acute infectious arthritis, because it requires acute operative intervention (saline washout of the joint) and antibiotics to minimize permanent damage to the joint and to prevent sepsis and death.
At all ages, rare causes include adjacent osteomyelitis, avascular necrosis, pigmented villonodular synovitis, hemarthrosis (eg, in hemophilia or coagulopathies), and tumors (see Table 4: Approach to the Patient With Joint Disease: Some Causes of Monarticular Joint Pain ).
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Table 4
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Some Causes of Monarticular
Joint Pain
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Cause
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Suggestive Findings
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Diagnostic Approach
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Avascular necrosis
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Joint pain in a patient with history of corticosteroid use or sickle cell disease
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X-ray plus CT or MRI
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Crystal-induced arthritis (uric acid, Ca pyrophosphate, Ca hydroxyapatite)
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Acute onset of severe pain, redness, swelling, particularly in the great toe or knee
Self-limited, episodic, recurrent symptoms common
Often a history of previous attacks or drug therapy with diuretics, hydrochlorothiazide, pyrazinamide, niacin, levodopa, or cyclosporine
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Arthrocentesis with cell counts, Gram stain, cultures, and crystal examination
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Hemarthrosis
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Acute onset spontaneously or after trauma; usually a significant effusion
Typically, a known bleeding disorder, hemoglobinopathy, or coagulopathy
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Arthrocentesis plus CT or MRI
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Osteoarthritis
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Slowly progressive pain in older, obese patients or patients who frequently use the affected joint (eg, in manual labor or high-impact sports)
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X-ray
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Osteomyelitis
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Fever and poorly localized pain without joint swelling or erythema
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X-ray plus bone scan, CT, or MRI
Sometimes CT-guided bone biopsy
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Periarticular syndromes (eg, bursitis, epicondylitis, fasciitis, tendinitis, tenosynovitis)
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Pain with specific joint movements or point tenderness and swelling over the bursa or tendon insertion site
Minimal to no symptoms at rest
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Clinical evaluation
MRI for suspected rotator cuff injury
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Septic arthritis (eg, bacterial, fungal, viral, mycobacterial, spirochetal)
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Acute onset of severe pain, redness, swelling, and decreased range of motion similar to that of crystal-induced arthropathy
High-risk patients include immunosuppressed people, IV drug users, diabetics, and those with risk factors for sexually transmitted diseases (eg, unprotected sex, multiple sex partners)
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Arthrocentesis with cell counts, Gram stain, cultures, and crystal examination
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Trauma or intra-articular derangement (eg, meniscal tear, osteonecrosis, fracture)
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Onset after trauma
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X-ray
Sometimes CT or MRI
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Tumor
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Slowly progressive constant joint pain
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X-ray
Sometimes CT or MRI
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Evaluation
Acute monarticular joint pain requires especially rapid diagnosis because some of its causes, particularly infectious (septic) arthritis and crystal-induced arthritis, require rapid treatment.
Evaluation should determine whether the joint or periarticular structures are the cause of symptoms and whether there is inflammation. If inflammation is present or the diagnosis is unclear, symptoms and signs of polyarticular and systemic disorders should be sought and all joints should be examined.
History
History of present
illness should focus on the acuity of onset (eg, abrupt, gradual), whether the problem is new or recurrent, and whether other joints have caused pain in the past. Also, temporal patterns (eg, diurnal variation, persistent vs intermittent), exacerbating and mitigating factors (eg, cold weather, activity), and any recent or past trauma to the joint should be noted. Patients should be specifically asked about unprotected sexual contact (possible gonococcal infection) and tick bites or residence in an area endemic for Lyme disease.
Review of systems should seek symptoms of causative disorders, including fever (infection), urethritis (gonococcal arthritis), and previous unexplained illness with skin rash (Lyme arthritis).
Past medical history should identify known joint disorders (particularly gout, osteoarthritis) and any known conditions that may cause monarticular joint pain (eg, coagulopathy, bursitis, tendinitis, hemoglobinopathy). Drug history should be reviewed for any use of anticoagulants, diuretics, or chronic corticosteroids. A family history also should be included.
Physical examination
Vital signs are reviewed for fever. Examination of the head, neck, and skin should note any signs of conjunctivitis, psoriatic plaques, mucosal lesions, ecchymoses, or malar rash. Genital examination should note any discharge or other findings consistent with sexually transmitted diseases.
Joints are inspected for deformities, erythema, and swelling. Range of motion is assayed, first actively and then passively; any crepitus on joint motion is noted.
Palpation is done to detect warmth, identify any effusion, and localize the area of tenderness. Of particular importance is whether the tenderness is directly over the joint line or adjacent to it (helping to differentiate an intra-articular from a periarticular disorder). Sometimes, compression of the joint without flexing or extending it (eg, pushing on the end of the great toe for patients with pain in the 1st metatarsophalangeal joint), sometimes with slight rotation, also helps differentiate intra-articular from periarticular disorders; this maneuver is not particularly painful for those with tendinitis or bursitis but is quite painful for those with arthritis. If the patient can tolerate it, the joint is stressed with various maneuvers to identify disruption of cartilage or ligaments (eg, in the knee, valgus and varus tests, anterior and posterior drawer tests, Lachman's test, and McMurray's test). Comparison with the contralateral unaffected joint often helps detect more subtle changes.
Large effusions in the knee are typically readily apparent. The examiner can check for minor knee effusions by pushing the suprapatellar pouch inferiorly and then pressing medially on the lateral side of the patella on an extended knee. This maneuver causes swelling to appear on the medial side.
Periarticular structures also should be examined to look for discrete soft swelling at the site of a bursa (bursitis), point tenderness at the insertion of a tendon (tendinitis), and point tenderness over a tendon with fine crepitus (tenosynovitis).
Red flags
The following findings are of particular concern:
Interpretation
of findings
Antecedent trauma suggests a fracture, meniscal tear, or hemarthrosis. In the absence of trauma, history and physical examination may suggest a cause, but testing is often necessary to rule out serious causes.
Acuteness of onset is a very important feature. Severe joint pain that develops over hours suggests crystal-induced arthritis or, less often, infectious arthritis. A previous attack of crystal-induced arthritis with development of similar symptoms suggests recurrence. Gradual onset of pain is typical of RA or noninfectious arthritis but can result from certain infectious arthritides (eg, mycobacterial, fungal).
Pain during rest and on initiating activity suggests inflammatory arthritis, whereas pain worsened by movement and relieved by rest suggests mechanical disorders (eg, osteoarthritis).
Pain worse with active than with passive joint motion may indicate tendinitis or bursitis; intra-articular inflammation generally restricts active and passive range of joint motion severely.
Increased warmth and erythema suggest inflammation, but erythema is often absent during inflammation. Tenderness or swelling at only one side of a joint, or away from the joint line, suggests an extra-articular origin (eg, in ligaments, tendons, or bursae); findings on several aspects of the joint suggest an intra-articular cause.
Although gout can involve many different single joints or combinations of joints, acute, painful monarticular arthritis of the metatarsophalangeal joint of a great toe (podagra) is especially suggestive.
The presence of systemic findings can help narrow the diagnosis. Urethritis can suggest gonococcal infection (although gonococcal arthritis often develops in patients without symptoms of urethritis). Fever is indicative of septic joint, crystal-induced arthropathy, or osteomyelitis. Symptoms indicating dermatologic, cardiac, or pulmonary involvement suggest diseases that are more commonly associated with polyarticular joint pain.
Testing
Joint aspiration (arthrocentesis) should be done in those with an effusion or other signs of inflammation (eg, erythema, warmth, fever). Studies of the joint fluid should include WBC count with differential (to determine whether the effusion is bloody or inflammatory), Gram stain and cultures, and microscopic examination for crystals. Finding crystals in synovial fluid confirms crystal-induced arthritis but does not rule out coexisting infection. A noninflammatory synovial fluid (eg, < 2000 WBCs or < 75% neutrophils) should lead to consideration of osteoarthritis, soft-tissue injury, or viral infection.
X-rays usually are done unless the cause is clearly a flare-up of a known disorder (eg, gout) or is clinically an obvious bursitis or tendinitis, which can often be diagnosed without further testing.
Other imaging tests (eg, CT, MRI, bone scan) are adjunctive and are done depending on what diagnoses are being considered (see Table 4: Approach to the Patient With Joint Disease: Some Causes of Monarticular Joint Pain).
Blood tests (eg, ESR, antinuclear antibodies, rheumatoid factor, anti-cyclic citrullinated peptide [CCP] antibody, HLA-B27 testing) may help support an early diagnosis of a noninfectious inflammatory arthritis.
Treatment
Overall treatment is directed at the underlying disorder.
Joint inflammation is usually treated symptomatically with NSAIDs. Pain without inflammation is usually more safely treated with acetaminophen. Joint immobilization with a splint or sling can sometimes relieve pain. Heat therapy may relieve muscle spasm around joints. Cold therapy may be analgesic in inflammatory joint diseases.
Physical therapy after the acute symptoms have lessened is useful to maintain range of motion and strengthen surrounding muscles.
Key
Points
Last full review/revision January 2009 by Jessica R. Berman, MD; Steven A. Paget, MD
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