Acute Monoarthritis: Diagnosis in Adults JONATHAN A

Acute Monoarthritis: Diagnosis in Adults JONATHAN A. BECKER, MD; JENNIFER P. DAILY, MD; and KATHERINE M. POHLGEERS, MD, MS University of Louisville, Louisville, Kentucky Acute monoarthritis can be the initial manifestation of many joint disorders. The most common diagnoses in the primary care setting are osteoarthritis, gout, and trauma. It is important to understand the prevalence of specific etiologies and to use the appropriate diagnostic modalities. A delay in diagnosis and treatment, particularly in septic arthritis, can have catastrophic results including sepsis, bacteremia, joint destruction, or death. The history and physical examination can help guide the use of laboratory and imaging studies. The presence of focal bone pain or recent trauma requires radiography of the affected joint to rule out metabolic bone disease, tumor, or fracture. If there is a joint effusion in the absence of trauma or recent surgery, and signs of infection (e.g., fever, erythema, warmth) are present, subsequent arthrocentesis should be performed. Inflammatory synovial fluid containing monosodium urate crystals indicates a high probability of gout. Noninflammatory synovial fluid suggests osteoarthritis or internal derangement. Pitfalls in the diagnosis and early treatment of acute monoarthritis include failure to perform arthrocentesis, administering antibiotics before aspirating the joint when septic arthritis is suspected (or failing to start antibiotics after aspiration), and starting treatment based solely on laboratory data, such as an elevated uric acid level. (Am Fam Physician. 2016;94(10):810-816. Copyright © 2016 American Academy of Family Physicians.) CME This clinical content onoarthritis refers to the clini- Symptoms consistent with osteoarthri- conforms to AAFP criteria cal presentation of pain or tis include pain that tends to worsen with for continuing medical swelling in a single joint.1 The activity, morning stiffness lasting less than education (CME). See 7 CME Quiz Questions on diagnosis can pose a consid- 30 minutes, and asymmetric joint pain. page 791. Merable challenge in the primary care setting The most commonly affected joints are the 7 Author disclosure: No rel- because the pain may be limited to the joint, hands, knees, hips, and spine. Although evant financial affiliations. or it may represent early manifestation of a osteoarthritis often follows an insidious systemic disease.2 Understanding the clinical course, acute flare-ups are common and can clues associated with potential diagnoses and be mistaken for other etiologies. The presence using an evidence-based, systematic clinical of focal bone pain or recent trauma requires approach are of utmost importance.3 A delay radiography of the affected joint to rule out in diagnosis and treatment, particularly with metabolic bone disease, tumor, or fracture.3,4 septic arthritis, can have catastrophic results Gout is a common disorder with a 3% including sepsis, bacteremia, joint destruc- prevalence worldwide. It accounts for more tion, or death.3-5 Pitfalls in the diagnosis than 7 million ambulatory visits in the and early treatment of acute monoarthritis United States annually.8,9 Crystal-induced include failure to perform arthrocentesis, arthritis presents as a rapidly developing administering antibiotics before aspirating monoarthritis with swelling and erythema, the joint when septic arthritis is suspected (or and most commonly involves the first meta- failing to start antibiotics after aspiration), tarsophalangeal joint.8 Over time, the joint and starting treatment based solely on labora- space can be irreversibly damaged with tory data, such as an elevated uric acid level.3-5 tophi formation.8,10 The presence of monosodium urate crystals indicates gout; these Etiology of Acute Monoarthritis crystals are identified by theirneedle-like Any condition that may cause joint pathol- appearance and strong negative birefrin- ogy can initially present as monoarthritis, gence3,8 (Figure 1 6). Calcium pyrophosphate resulting in a broad differential diagnosis1 dihydrate crystals are polymorphic, weakly (Table 16). Because of this, monoarthritis positive under birefringent microscopy, and has no unifying etiology. The most common their presence indicates pseudogout.3 Other diagnoses in the primary care setting are crystal-induced arthritis etiologies include osteoarthritis, gout, and trauma.3 calcium oxalate and hydroxyapatite.1 810Downloaded American from the Family American Physician Family Physician website at www.aafp.org/afp.www.aafp.org/afp Copyright © 2016 American AcademyVolume of Family94, Number Physicians. 10 For◆ November the private, 15,noncom 2016- mercial use of one individual user of the website. All other rights reserved. Contact [email protected] for copyright questions and/or permission requests. Acute Monoarthritis Table 1. Causes of Acute Monoarthritis Common Less common (continued) Avascular necrosis Hemoglobinopathies Crystals Juvenile rheumatoid arthritis of the causative agent through synovial fluid Calcium oxalate Loose body culture is essential for the diagnosis and 12 Calcium pyrophosphate dihydrate Psoriatic arthritis guidance of antibiotic therapy. (pseudogout) Reactive arthritis Less common causes of monoarthritis Hydroxyapatite Rheumatoid arthritis include systemic diseases such as spondy- Monosodium urate (gout) Sarcoidosis loarthropathies (e.g., psoriatic arthritis, Hemarthrosis Systemic lupus erythematosus reactive arthritis, ankylosing spondylitis), Infectious arthritis Rare sarcoidosis, Behçet syndrome, systemic lupus 1 Bacteria Amyloidosis erythematosus, and rheumatoid arthritis. Fungi Behçet syndrome Rheumatic diseases and corticosteroid use 1 Lyme disease Familial Mediterranean fever can cause avascular necrosis of the bone. Mycobacteria Foreign-body synovitis Virus Hypertrophic pulmonary Diagnosing Acute Monoarthritis Internal derangement osteoarthropathy The diagnosis of acute monoarthritis begins Osteoarthritis Intermittent hydrarthrosis with a comprehensive history and physical Osteomyelitis Pigmented villonodular synovitis examination to reveal potential diagnostic Overuse Relapsing polychondritis clues3,6,17 (Table 2 1,3,6,12,18,19). Key elements of Trauma Synovial metastasis the patient history include a review of systems, Less common Synovioma age, previous joint disease, recent trauma, Ankylosing spondylitis Systemic onset juvenile medication use, family history of gout, con- Bone malignancies idiopathic arthritis (Still disease) current illness, sexual history, diet, travel his- Bowel disease–associated arthritis Vasculitic syndromes tory, tick bites, alcohol use, intravenous drug use, and an occupational assessment.3,6,17 Adapted with permission from Siva C, Velazquez C, Mody A, Brasington R. Diagnos- Symptoms that worsen with activity and ing acute monoarthritis in adults: a practical approach for the family physician. Am Fam Physician. 2003;68(1):85. improve with rest suggest a mechanical process, whereas symptoms with an inflammatory process often worsen with rest and Infection is a common etiology of joint pain. When present with morning stiffness.1 Osteoarthritis often infection is suspected in the presence of a joint effu- starts as mild joint inflammation that may initially sion or inflammation, arthrocentesis should be per- arouse suspicion for new-onset inflammatory diseases, formed, in addition to further laboratory testing as indicated (Figure 2 6). (A video of arthrocentesis of the knee is available at https://www.youtube.com/ watch?v=fZ2dcZhoGP8.) Gonococcal arthritis is the most common type of nontraumatic acute monoarthritis in young, sexually active persons in the United States.11 Septic arthritis is a key consideration in adults presenting with acute monoarthritis, particularly in the presence of joint pain, erythema, warmth, and immobility.12 The most important risk factors for septic arthritis are a prosthetic joint, skin infection, joint surgery, rheumatoid arthritis, age older than 80 years, diabetes mellitus, and renal disease.11 One study found that among persons presenting with acute joint pain and a predisposing condition, 10% had septic arthritis.4 When septic arthritis is suspected, it is important to begin empiric antibiotics immediately following arthrocentesis, because failure to Figure 1. Needle-shaped monosodium urate crystals visible with light microscopy of synovial fluid in a patient initiate prompt antibiotic therapy can lead to subchon- with gout. dral bone loss and permanent joint dysfunction.5,11,12 The Reprinted with permission from Siva C, Velazquez C, Mody A, Brasington R. most common route of entry into the joint is hematog- Diagnosing acute monoarthritis in adults: a practical approach for the fam- enous spread during bacteremia4,12-16; therefore, isolation ily physician. Am Fam Physician. 2003;68(1):89. November 15, 2016 ◆ Volume 94, Number 10 www.aafp.org/afp American Family Physician 811 Acute Monoarthritis Diagnosis of Acute Monoarthritis Complete history and physical examination History of trauma or focal bone pain? Rule out soft tissue problems around the joint Yes No Plain film radiography A Joint effusion or inflammation? Fracture, Osteoarthritis, Yes No No effusion but avulsion chondrocalcinosis severe symptoms Arthrocentesis Consider laboratory tests; Referral Go to A complete blood count, Consider referral; patient erythrocyte sedimentation may need computed rate, and uric acid level tomography or MRI for diagnosis, or ultrasonography to guide arthrocentesis

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