Rheumatology: 4. Acute Monoarthritis Review Synthèse
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Clinical basics Rheumatology: 4. Acute monoarthritis Review Synthèse Jolanda Cibere Dr. Cibere is a Medical The case Research Council of Canada Mrs. R, a 72-year-old woman with a history of osteoarthritis of the knees, con- Clinician Scientist Fellow sults her physician because she has a fever, malaise and a swollen, painful at the University of British right knee. She is unable to bear weight on her right leg because of the pain. Columbia, and is with the Two years earlier she experienced gastrointestinal bleeding while taking nons- Arthritis Research Centre of teroidal anti-inflammatory drugs for osteoarthritis; currently, she is taking only Canada, Vancouver, BC acetaminophen as needed for pain. Mrs. R is otherwise healthy and has not travelled recently. During examination the physician finds that Mrs. R is slightly confused. Her pulse rate is 80 beats/min and regular; her blood pres- This article has been peer reviewed. sure is normal, and her temperature is 37.9°C. Her right knee is warm, erythe- CMAJ 2000;162(11):1577-83 matous, swollen and tender. Flexion ranges from 10° to 80° with pain. Her leukocyte count is above normal at 14.8 × 109 cells/L (normal range: 4–11 × This series has been reviewed 109 cells/L). Her serum uric acid level, measured at an earlier office visit, was and endorsed by the Canadian slightly above normal at 450 µmol/L (normal range: 90–360 µmol/L). Rheumatology Association. The Arthritis Society salutes CMAJ cute monoarthritis is a potential medical emergency that must be investi- for its extensive series of articles gated and treated promptly. Common diagnoses include crystal-induced on arthritis. The Society believes A arthritis and mechanical complications of osteoarthritis, fractures and liga- that this kind of information is mentous or meniscal injury; less common causes are ischemic necrosis (osteo- crucial to educating physicians necrosis), hemarthrosis or tumour. However, first and foremost, acute monoarthri- about this devastating disease. tis should be considered septic until proven otherwise. An accurate diagnosis of acute monoarthritis depends on a good history and physi- Series editor: Dr. John M. Esdaile, cal examination that are supplemented by the appropriate investigations. In particu- Professor and Head, Division of lar, the physician must verify that the patient has arthritis, as manifested by joint Rheumatology, University of British swelling, and that the arthritis is limited to a single joint.1,2 Determining whether the Columbia, and Scientific Director, arthritis is inflammatory or mechanical in nature and whether the disease is acute or Arthritis Research Centre of chronic will then help the physician arrive at a presumptive diagnosis. Canada, Vancouver, BC. Investigations should include joint aspiration of synovial fluid for a leukocyte count, Gram’s stain, cultures and an examination for crystals; radiographs of the joint may also be required. Occasionally, a radionuclide scan, computed tomography (CT) or magnetic resonance imaging (MRI) is useful. Treatment is based on the underly- ing diagnosis, but antibiotics are sometimes required until septic arthritis is excluded. If acute monoarthritis is apparent from the history and physical examination the most common differential diagnoses are infectious arthritis, crystal-induced arthri- tis and trauma-induced arthritis3 (Fig. 1); these can be differentiated by history, physical examination and synovial fluid analysis4 (Table 1). Causes Infectious arthritis Acute monoarthritis should be considered infectious until proven otherwise.5–7 Septic arthritis is usually caused by an infectious agent that is spread through the blood system. It often affects the knee and is characterized by systemic symptoms of sepsis (e.g., fever and malaise), as well as swelling, warmth and local pain in the involved joint, sometimes so severe that the patient refuses to allow even passive movement. Redness around the joint is an important clue, limiting diagnosis to ei- ther infectious or crystal-induced arthritis. CMAJ • MAY 30, 2000; 162 (11) 1577 © 2000 Canadian Medical Association or its licensors Cibere 7,21,30 Fig. 1: The diagnosis and management of acute monoarthritis. 1578 JAMC • 30 MAI 2000; 162 (11) Acute monoarthritis The inflammatory response may be blunted in immuno- in any joint, but predominantly affects the first metatar- compromised patients (such as those taking immuno- sophalangeal joints, midfoot, ankles or knees. Pseudogout, suppressants); patients with rheumatoid arthritis, diabetes caused by calcium pyrophosphate dihydrate crystal deposi- mellitus or HIV; intravenous drug users and those with tion, affects mainly the knees and wrists, but can occur in prosthetic joints. However, suspicion of infectious arthritis the first metatarsophalangeal and other joints as well. in these patients should be maintained, despite limited An important clue in the diagnosis of crystal-induced physical signs, until infection has been excluded. arthritis is a history of acute attacks of monoarthritis that Staphylococcus aureus causes most nongonococcal cases of resolved spontaneously. Crystal-induced arthritis is charac- septic arthritis in adults.5–8 However, gonococcal infections terized by redness around the joint, and it can present with are the most common cause of septic arthritis in sexually fever, mimicking infectious arthritis. With gout the pain is active young adults.9,10 These cases are often characterized often so severe that patients complain of an inability to tol- by migratory arthritis and associated with tenosynovitis and erate the weight of a light bed sheet on the involved joint. maculopapulovesicular skin lesions before manifesting as a Tophi — deposits of urate crystals — in soft tissues is monoarthritis. highly suggestive of chronic gout. Tophi appear as soft, Although arthritides caused by mycobacteria and fungi subcutaneous nodules usually on fingers and toes, around are usually chronic in nature, they can also resemble acute the elbows and, classically, on the helix of the ear. They can monoarthritis. If the patient’s history suggests prior tuber- be differentiated from rheumatoid nodules by their asym- culosis, recent exposure to tuberculosis or an immuno- metric distribution, yellow–white appearance and occa- depressed state, mycobacterial or fungal arthritis should be sional overlying skin erythema. considered. Viruses such as hepatitis B, HIV and human parvovirus Noninflammatory monoarthritis and the spirochete Borrelia burgdorferi, which causes Lyme disease, rarely cause acute monoarthritis; they more com- Trauma causing fractures (or microfractures), as well as monly manifest as acute or chronic oligoarthritis. ligamentous or meniscal injuries, can lead to acute monoarthritis. It is often associated with mild-to-moderate Crystal-induced arthritis joint swelling, and the pain is characteristically exacerbated on movement and relieved at rest. Although a history of Crystal-induced arthritis is another main cause of acute trauma is usually evident, this may not be the case for pa- monoarthritis. Gout, which is caused by monosodium urate tients with osteoporosis. The pain of traumatic arthritis is crystals in the synovial fluid, can give rise to acute arthritis felt within seconds to minutes of the trauma, in contrast to Table 1: Differential diagnosis of acute monoarthritis3,4 Possible diagnosis Cause History and physical examination Synovial fluid analysis Common pitfalls Infectious arthritis Bacteria Severe joint pain and tenderness Opaque Inflammatory response may Mycobacteria Heat, marked swelling Leukocyte count elevated be blunted in immuno- × 9 compromised patient Fungi Redness (often > 100 10 /L) Culture may be negative if PMNs > 85% Spirochetes causing Lyme Patient unable to move joint; patient previously treated disease often refuses passive movement Culture positive with antibiotics Viruses (e.g., HIV, hepatitis B) Patient unable to bear weight Crystal-induced Monosodium urate crystals Severe joint pain and tenderness Translucent Patient may have con- comitant infectious arthritis arthritis (gout) Heat, marked swelling Leukocyte count Calcium pyrophosphate di- × 9 with positive culture Redness 1–75 10 /L hydrate crystals (pseudogout) Patient unable to move joint and Often > 50% PMNs Apatite crystals often refuses passive movement Culture negative Calcium oxalate crystals Patient often unable to tolerate Crystals positive any pressure on joint Trauma-induced Fracture Joint tenderness on movement Fluid transparent or History of trauma may not be arthritis Internal derangement Warmth, mild-to-moderate swelling blood stained elicited with osteoporosis Hemarthrosis No redness Leukocyte count < 1 × 109/L Pain worse with activity History of trauma; onset of pain within minutes of trauma HIV = human immunodeficiency virus, PMN = polymorphonuclear leukocyte. CMAJ • MAY 30, 2000; 162 (11) 1579 Cibere the pain of infectious and crystal-induced arthritis which in differentiating inflammatory from noninflammatory often develops over hours. Acute hemarthrosis (bleeding arthritis. Therapeutic indications for joint aspiration in- into a joint) should be suspected in patients with bleeding clude draining of a tense effusion to relieve pain and im- disorders and in those taking anticoagulants. prove function, as well as draining of pus or blood to avoid Other noninflammatory permanent joint damage.17 Syno- causes of monoarthritis include vial fluid analysis should include osteoarthritis and osteonecrosis. Key points