NUR 560 Module 8 Focused Assessment Example

Two Answers in One Knee: Gout, Septic Arthritis and the Case for Aspiration in a 67-Year-Old Man

[Student Name]

Southern New Hampshire University

NUR 560: Advanced Health Assessment and Clinical Reasoning

Focused Assessment

[Instructor Name]

[Date]

The organization, setting and figures below are a composite written as a model document. No real employer, client, colleague or patient is described.

Two Answers in One Knee: Gout, Septic Arthritis and the Case for Aspiration in a 67-Year-Old Man

A single hot, swollen joint in an older adult is usually crystal disease, but the diagnosis that must not be missed is septic arthritis, which can destroy cartilage within days and carries real mortality. The two look alike at the bedside, and a history of gout invites a quick conclusion. This assessment examines a composite 67-year-old man with an acutely swollen knee. It argues that the joint must be aspirated before any diagnosis is accepted, that synovial fluid results should be read as likelihood ratios rather than cutoffs, and that finding urate crystals does not exclude a coexisting infection.

Focused History

His right knee became painful and swollen over about 24 hours and now hurts with any movement. He felt feverish overnight. He has had three gout attacks in the left big toe over four years, each settling with colchicine, and takes hydrochlorothiazide for hypertension. He also has type 2 diabetes. Five days ago he scraped his right shin while clearing brush, and the wound is healing. He has no knee injury, no joint replacement, no recent sexual contacts outside a long marriage, no tick bites and no diarrhea or eye symptoms.

The questions were chosen to weigh each hypothesis. Earlier gout attacks and a thiazide raise the probability of a gout flare. Diabetes, older age and a recent skin break raise the risk of a bloodborne joint infection. Trauma points to hemarthrosis; new sexual partners to gonococcal arthritis; recent diarrhea or eye inflammation to reactive arthritis; and tick exposure to Lyme arthritis.

Focused Examination

Temperature is 38.3°C, heart rate 98 and blood pressure 146/82 mm Hg. The right knee is warm and red with a large effusion, confirmed by a positive bulge sign and ballottement of the patella. Passive flexion beyond 30 degrees causes severe pain. The superficial abrasion on the right shin is clean, with no spreading redness. There are no tophi, no other swollen joints, no rash and no genital lesions.

The examination separates a true joint effusion from nearby soft tissue problems. In prepatellar bursitis, swelling sits in front of the kneecap and gentle passive movement is usually tolerated; pain on even small passive movement and a palpable effusion point inside the joint.

Why the Knee Must Be Tapped

A history of gout cannot confirm that this attack is gout, and fever does not reliably separate gout from infection, because both can raise temperature and inflammatory markers. A systematic review of the bedside diagnosis of septic arthritis found that the peripheral white count and erythrocyte sedimentation rate did little to separate septic arthritis from other causes, and that synovial fluid analysis carried most of the diagnostic information (Margaretten et al., 2007). The review reported that a synovial white count of 100,000 cells per microliter or more had a positive likelihood ratio of about 28, a count of 50,000 or more about 7.7 and a count below 25,000 about 0.32 (Margaretten et al., 2007). Those figures mean no single threshold rules infection in or out; each result moves the probability by a known amount. Aspiration before any antibiotic is given is therefore the essential step.

Synovial Fluid Results

Aspiration yielded 60 mL of cloudy yellow fluid. The white count was 62,000 cells per microliter with 92% neutrophils. Polarized microscopy showed needle-shaped, negatively birefringent crystals inside neutrophils, consistent with monosodium urate. The Gram stain showed no organisms. Fluid and two sets of blood cultures were sent.

Urate crystals in fluid from a symptomatic joint are sufficient on their own to classify the joint disease as gout (Neogi et al., 2015). But a white count above 50,000 carries a likelihood ratio of about 7.7 for infection, and a negative Gram stain does not exclude it. Gout and septic arthritis can coexist, and crystals can be shed into a joint that is infected. His results support gout while leaving infection firmly on the list.

Problem Representation and Ranked Differential

Summary: a 67-year-old man with diabetes, earlier gout and a recent skin break who has 24 hours of fever and an acute right knee effusion, with synovial fluid showing 62,000 white cells, 92% neutrophils, urate crystals and a negative Gram stain.

1. Septic arthritis, possibly coexisting with gout. Ranked first because it is the diagnosis that cannot wait. For: fever, diabetes, skin break, age, synovial count above 50,000. Against: crystals offer another explanation, and the Gram stain is negative.

2. Acute gout flare. For: earlier attacks, thiazide use, intracellular urate crystals. Against: the knee is an unusual site for him, and the count is high.

3. Calcium pyrophosphate crystal arthritis. Against: crystals seen were needle-shaped and negatively birefringent, not the rhomboid, positively birefringent crystals of this condition.

4. Prepatellar bursitis. Against: true effusion and severe pain on passive motion.

5. Hemarthrosis. Against: no trauma or anticoagulant, cloudy rather than bloody fluid.

Plan and What Would Change It

Because infection cannot be excluded, he is admitted for intravenous antibiotics covering Staphylococcus aureus and streptococci, started after aspiration and cultures, with orthopedic review for joint drainage if infection is confirmed. His gout is treated at the same time, since a flare is also present; guidance supports colchicine, an anti-inflammatory drug or a glucocorticoid for flares, and recommends considering an alternative to hydrochlorothiazide when feasible (FitzGerald et al., 2020). A glucocorticoid injection into the joint is avoided until infection is excluded.

A negative culture at 48 to 72 hours, with a falling fever and improving knee, would allow antibiotics to stop and the diagnosis to rest on gout alone. A positive culture confirms septic arthritis and sets the length of therapy. His fluid culture grew methicillin-susceptible Staphylococcus aureus on day two, so he had both conditions.

Why a Quick Diagnosis Would Have Failed

Had the knee been treated as another gout attack based on his history, or had the reasoning stopped once crystals appeared, the infection would have progressed untreated. Both errors come from accepting the first adequate explanation. Deciding in advance that one finding, crystals, would not be allowed to close the question of infection is what protected this patient, and it is a habit worth carrying into every acute monoarthritis.

Conclusion

This man's hot knee held two answers. Aspiration was essential, the synovial white count was interpreted as a shift in probability rather than a cutoff, and the discovery of urate crystals was not allowed to exclude infection. Treating both conditions while waiting for culture was the safe course, and the culture confirmed that it was the correct one.

References

FitzGerald, J. D., Dalbeth, N., Mikuls, T., Brignardello-Petersen, R., Guyatt, G., Abeles, A. M., Gelber, A. C., Harrold, L. R., Khanna, D., King, C., Levy, G., Libbey, C., Mount, D., Pillinger, M. H., Rosenthal, A., Singh, J. A., Sims, J. E., Smith, B. J., Wenger, N. S., . . . Neogi, T. (2020). 2020 American College of Rheumatology guideline for the management of gout. Arthritis Care & Research, 72(6), 744-760. https://doi.org/10.1002/acr.24180

Margaretten, M. E., Kohlwes, J., Moore, D., & Bent, S. (2007). Does this adult patient have septic arthritis? JAMA, 297(13), 1478-1488. https://doi.org/10.1001/jama.297.13.1478

Neogi, T., Jansen, T. L. T. A., Dalbeth, N., Fransen, J., Schumacher, H. R., Berendsen, D., Brown, M., Choi, H., Edwards, N. L., Janssens, H. J. E. M., Lioté, F., Naden, R. P., Nuki, G., Ogdie, A., Perez-Ruiz, F., Saag, K., Singh, J. A., Sundy, J. S., Tausche, A.-K., . . . Taylor, W. J. (2015). 2015 gout classification criteria: An American College of Rheumatology/European League Against Rheumatism collaborative initiative. Arthritis & Rheumatology, 67(10), 2557-2568. https://doi.org/10.1002/art.39254