Rheumatoid arthritis (RA) and gouty arthritis (GA) are two common forms of joint inflammation that can present with very similar physical symptoms, making them difficult to tell apart early in the disease process. Accurate and early differentiation is crucial because the treatment strategies and long-term management for the two conditions are substantially different.

The primary purpose of this observational study is to evaluate the diagnostic performance of musculoskeletal ultrasound (MSUS) in distinguishing between RA and GA. Ultrasound is a safe, radiation-free imaging tool that can visualize joint inflammation and structural changes in real-time. This study utilizes a structured semi-quantitative scoring system (graded on a scale of 0 to 3) to systematically measure the severity of joint lining thickness (synovial hypertrophy) and active blood flow (power Doppler signal). It also checks for crystal-related deposits, such as tophi or the double contour sign, which are highly suggestive of gout.

Participants aged 18 and older with suspected or confirmed RA or GA who are referred for joint assessment at Assiut University Hospitals will undergo a standard clinical evaluation, routine laboratory testing, and an ultrasound examination of specific target joints (such as the wrists, hands, knees, and ankles). By comparing the ultrasound scores and specific structural findings between the two patient groups, the study aims to establish a reliable, standardized imaging approach to help physicians make faster, more confident diagnoses and initiate the correct disease-specific therapies sooner.

Inclusion Criteria:

• Patients aged 18 years or older.
• Either sex.
• Patients with clinically suspected or confirmed rheumatoid arthritis.
• Patients with clinically suspected or confirmed gouty arthritis.
• Patients referred for musculoskeletal ultrasound assessment of painful, swollen, or inflamed joints.
• Patients able and willing to provide informed consent.
• Patients whose final diagnosis is established by clinical assessment, laboratory testing, and/or relevant imaging or synovial fluid analysis when available.

Exclusion Criteria:

• Patients younger than 18 years.
• Patients with septic arthritis or suspected joint infection.
• Patients with traumatic joint injury involving the target joint.
• Patients with other inflammatory arthropathies such as psoriatic arthritis, reactive arthritis, or systemic lupus erythematosus if they may confound imaging interpretation.
• Patients with advanced osteoarthritis in the scanned joint if it markedly limits Faculty of Medicine Institutional Review Board (IRB) Assiut Medical School Research Proposal Form 5 interpretation.
• Patients with incomplete clinical records or insufficient ultrasound windows.
• Patients who refuse consent.
• Patients whose diagnosis remains uncertain after clinical workup.

The study population consists of adult patients, aged 18 years or older, of either sex. It includes individuals presenting with clinically suspected or confirmed rheumatoid arthritis or gouty arthritis. These participants are specifically those referred to the radiology department at Assiut University Hospitals in Assiut, Egypt, for a musculoskeletal ultrasound assessment of painful, swollen, or inflamed joints.