Chapter 52
Acute Joint Pain (Case 44)
Robin Dibner MD, Joel Mathew MD, and Jessica L. Israel MD
Case: A 45-year-old man presents to the emergency department complaining of pain, swelling, and redness in his right knee and inability to walk for 1 day. The symptoms appeared acutely yesterday without any history of trauma. No other joints were painful. He also felt feverish but did not take his temperature; he had no relief with acetaminophen. Past medical history is significant for hypertension controlled with hydrochlorothiazide and a kidney stone 5 years ago. He was recently divorced but has been sexually active, and he has had no recent travel or insect bites. He drinks two to three glasses of wine nightly. There is no family history of arthritis or gout. The review of systems is negative for rash, sore throat, history of heart murmur, recent dental work, inflammatory bowel disease, urethral discharge, or any recent infection. Physical examination shows a temperature of 101°F and a tender, warm, erythematous, swollen right knee.
Differential Diagnosis
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Nongonococcal septic arthritis
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Gonococcal arthritis
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Gout
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Pseudogout/calcium pyrophosphate dihydrate (CPPD) deposition
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Viral arthritis
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Speaking Intelligently
When seeing a patient with acute arthritis, it is necessary to think first of the potential emergencies: undiagnosed trauma and septic joint. The former diagnosis, which is handled by orthopedic surgeons, is usually easily eliminated by the physical exam, negative radiographs, and non-bloody joint fluid. Septic joints, which require laboratory confirmation, are an emergency because antibiotics must be initiated quickly and the fluid drained from the joint to reduce the risk of damage from inflammatory mediators and collagenases. Untreated septic joints can show radiographic changes in as little as a week, and there may be irreversible joint damage if drainage is inadequate; the general approach is to treat presumptively while awaiting confirmation by Gram stain and culture.
• When evaluating a patient with a new monoarthropathy, the most important focus is to obtain joint fluid for an accurate diagnosis.
• If the patient has a septic joint and appropriate therapy is not initiated as soon as possible, there is a risk of permanent joint destruction and disability.
• In cases in which aspiration of the affected joint is not possible (perhaps because of available resources or experience), treating for the possibility of septic arthritis until a definitive diagnosis can be made is extremely important.
• A prior history of an acute episode of arthritis suggests a crystal-induced process. Fifty percent of gout patients have a first episode in the first metatarsophalangeal (large toe) joint; historically, that classic presentation is called podagra. Middle age (older for women), obesity, alcoholism, thiazide or cyclosporine use, and a family history of gout are all risk factors.
• Pseudogout (CPPD deposition disease) is associated with hypothyroidism, hyperparathyroidism, hemochromatosis, and osteoarthritis.
• Obtaining a history of a prior diagnosis or current symptoms of a sexually transmitted disease (STD) is critical, as disseminated gonococcal infection is a common cause of septic arthritis.
• Any history of underlying joint abnormality, such as prior arthritis or prosthetic joint replacement, puts the patient at higher risk of septic arthritis.
• The pattern of joint involvement is important in suggesting a diagnosis.
• Fifty percent of first attacks of gout occur in a first metatarsophalangeal joint, the classic presentation called podagra. The knee and ankle are the next most common; upper extremity involvement is rarely seen unless the disease is long-standing.
• Tophi, deposits of uric acid seen in some patients with long-standing untreated gout, are palpable subcutaneous deposits of uric acid usually felt in the olecranon bursa or along the proximal ulnar surface.
• Pseudogout generally affects the knees and wrists.
• As the vast majority of septic arthritis is caused by hematogenous spread, any joint can be involved. The knee is the most common.
• Infection of an axial skeletal joint, such as the sternoclavicular joint, is characteristic of the high-grade bacteremia that can be seen in patients with Staphylococcus aureus endocarditis.
• Clinical findings in gonococcal arthritis depend on the stage of the disease. Classically the earlier infection is characterized by a migratory joint pattern where one joint is inflamed but resolves before another is involved. Extensor tenosynovitis of the wrist or ankle is common. There is often a rash in this phase with a very small number of individual pustules, each on an erythematous base. A monoarticular septic joint is considered a later manifestation but often is present at the time of diagnosis.
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