Diagnosis: Likely Inflammatory Arthritis (Rheumatoid Arthritis or Polymyalgia Rheumatica) with Peripheral Neuropathy
This 70-year-old woman with knee pain, difficulty making a fist, numbness, and no joint swelling most likely has an inflammatory arthritis (particularly rheumatoid arthritis or polymyalgia rheumatica) with concurrent peripheral neuropathy, rather than gout, given the normal uric acid and absence of joint swelling. 1
Why This Is NOT Gout
Normal uric acid does NOT exclude gout, but the clinical presentation argues strongly against it:
- While approximately 10% of gout patients have normal serum uric acid during acute attacks, gout typically presents with rapid onset (6-12 hours) of severe pain, swelling, and erythema—not the chronic presentation described here 1
- The absence of joint swelling makes gout highly unlikely, as visible swelling is a cardinal feature of acute gout attacks 1
- Difficulty making a fist suggests small joint involvement (hands), which combined with knee pain suggests a polyarticular process rather than the typical monoarticular podagra presentation of gout 1
- Numbness is not a feature of gout and suggests a neurological component 2
Diagnostic Workup Algorithm
Immediate laboratory testing should include:
- Rheumatoid factor (RF) and anti-CCP antibodies to evaluate for rheumatoid arthritis 1
- Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) to assess for inflammatory activity 1
- Complete blood count to evaluate for anemia of chronic disease 1
- Metabolic panel to assess for comorbidities including diabetes (which could explain numbness) 1, 3
If joint effusion is present on examination:
- Joint aspiration with synovial fluid analysis is mandatory for any undiagnosed inflammatory arthritis, examining for monosodium urate crystals (gout), calcium pyrophosphate crystals (pseudogout), cell count, Gram stain, and culture 1
- Synovial fluid to serum uric acid ratio ≥1.01 has 89.6% sensitivity and 66.3% specificity for gout when crystal analysis is unavailable 4
Imaging recommendations:
- Knee radiographs (anteroposterior, lateral, and tangential patellar views) should be obtained initially to evaluate for osteoarthritis, chondrocalcinosis, or erosive changes 1
- Hand radiographs are indicated given difficulty making a fist, to assess for erosive changes of rheumatoid arthritis 1
- MRI of the knee may be appropriate if radiographs are normal but symptoms persist, particularly to evaluate for synovitis, bone marrow edema, or meniscal pathology 1
Management Approach
Pending definitive diagnosis:
- Refer to rheumatology for comprehensive evaluation, as inflammatory arthritis requires disease-modifying therapy to prevent joint damage and disability 1
- Evaluate the numbness separately with neurological examination including assessment of sensation distribution, reflexes, and motor strength 2
- Consider nerve conduction studies if peripheral neuropathy is confirmed clinically 2
- Assess for metabolic syndrome features (obesity, hyperglycemia, hyperlipidemia, hypertension) as these are common comorbidities in inflammatory arthritis 1
Critical Pitfalls to Avoid
Do not diagnose gout based on hyperuricemia alone or exclude it based on normal uric acid—crystal identification is the gold standard 1, 3
Do not delay rheumatology referral: Early inflammatory arthritis requires prompt treatment with disease-modifying antirheumatic drugs (DMARDs) within weeks to months to prevent irreversible joint damage 1
Do not overlook the numbness: This symptom requires separate neurological evaluation as it is not explained by inflammatory arthritis alone and may indicate diabetic neuropathy, cervical radiculopathy, or peripheral neuropathy from other causes 2
Do not assume osteoarthritis based on age alone: The combination of polyarticular involvement, difficulty with hand function, and systemic symptoms suggests inflammatory rather than degenerative arthritis 1