Musculoskeletal High-Yield: OA, RA, Gout, and Back Pain for FNP Boards
Clinical High-Yield · 10 min read · April 28, 2026
Musculoskeletal questions on the FNP boards are fundamentally about pattern recognition. The boards give you a joint distribution, a set of associated findings, and a lab result — and they want to know if you can name the disease. Master the patterns, and MSK becomes one of the most predictable sections on the exam.
Osteoarthritis vs. Rheumatoid Arthritis: The Classic Distinction
This comparison appears on virtually every FNP board exam in some form. Know it cold.
Osteoarthritis (OA) is a degenerative joint disease caused by cartilage breakdown. It affects weight-bearing joints (knees, hips) and the distal interphalangeal (DIP) joints of the hands. The classic hand findings are Heberden's nodes (DIP) and Bouchard's nodes (PIP). Pain is worse with activity and improves with rest. Morning stiffness lasts less than 30 minutes. There is no systemic inflammation — ESR and CRP are normal. X-ray shows joint space narrowing, osteophytes (bone spurs), subchondral sclerosis, and subchondral cysts.
Rheumatoid Arthritis (RA) is an autoimmune, inflammatory arthritis. It affects the small joints of the hands and feet symmetrically — specifically the MCP and PIP joints (sparing the DIP). Morning stiffness lasts more than 1 hour. Systemic features include fatigue, weight loss, and low-grade fever. Lab findings: elevated ESR and CRP, positive rheumatoid factor (RF) in ~80% of patients, and positive anti-CCP antibody (more specific than RF). X-ray shows periarticular osteopenia and joint erosions. Classic deformities: ulnar deviation, swan-neck deformity, boutonnière deformity.
Board Pearl: The boards love to test the DIP vs. MCP/PIP distinction. OA = DIP (Heberden's nodes). RA = MCP and PIP (sparing DIP). If the question mentions DIP involvement, think OA or psoriatic arthritis — not RA.
Treatment: OA first-line is acetaminophen and NSAIDs, with topical diclofenac for localized disease. RA first-line is methotrexate (the anchor DMARD), with hydroxychloroquine, sulfasalazine, and leflunomide as alternatives. Biologics (TNF inhibitors like etanercept, adalimumab) are added for inadequate response to DMARDs.
Gout: The Boards' Favorite Crystal Arthropathy
Gout is caused by monosodium urate crystal deposition in joints. The classic presentation: sudden-onset, exquisitely painful monoarthritis of the first MTP joint (podagra) in a middle-aged man with a history of hyperuricemia, alcohol use, or diuretic use. The joint is red, hot, swollen, and tender to even light touch.
Diagnosis: Arthrocentesis (joint aspiration) is the gold standard — it shows negatively birefringent, needle-shaped urate crystals under polarized light. Serum uric acid may be normal during an acute attack (it drops as crystals precipitate), so it is not diagnostic.
Acute treatment: NSAIDs (indomethacin is the classic choice), colchicine (most effective if started within 24 hours), or corticosteroids (for patients who cannot take NSAIDs or colchicine).
Chronic management: Urate-lowering therapy (ULT) is indicated for patients with recurrent attacks (≥2/year), tophi, uric acid nephrolithiasis, or chronic gouty arthropathy. Allopurinol is first-line ULT — it inhibits xanthine oxidase and reduces uric acid production. Target uric acid is <6 mg/dL (<5 mg/dL with tophi). Do not start allopurinol during an acute attack — it can prolong or worsen the flare.
Pseudogout is caused by calcium pyrophosphate crystal deposition. It affects larger joints (knee is most common) and presents similarly to gout. Crystals are positively birefringent and rhomboid-shaped under polarized light. Treatment is the same as acute gout (NSAIDs, colchicine, steroids).
Back Pain: Red Flags and the 6-Week Rule
Low back pain is one of the most common presentations in primary care, and the boards test it heavily. The key clinical skill is distinguishing mechanical back pain (the vast majority) from back pain with a serious underlying cause.
Red flags that require urgent workup:
- Saddle anesthesia, bowel or bladder dysfunction → cauda equina syndrome (surgical emergency)
- Fever, IV drug use, immunosuppression → spinal epidural abscess or discitis
- History of cancer + new back pain → metastatic disease
- Age >50 with new back pain, unexplained weight loss → malignancy
- Pain worse at rest or at night (not relieved by lying down) → inflammatory or malignant cause
Mechanical back pain (no red flags) is managed conservatively for 4–6 weeks before imaging is indicated. First-line treatment: NSAIDs, continued activity (bed rest is harmful), and physical therapy. Imaging (X-ray or MRI) before 6 weeks is not indicated for uncomplicated mechanical back pain — this is a high-yield board concept.
Lumbar radiculopathy (sciatica) presents with pain radiating down the leg in a dermatomal distribution, often with numbness or weakness. The straight leg raise (SLR) test is positive when leg pain is reproduced between 30–70 degrees of hip flexion. Most cases resolve with conservative management. MRI is indicated if symptoms persist beyond 6 weeks or if there are neurological deficits.
Fibromyalgia: The Diagnosis of Exclusion
Fibromyalgia is a central sensitization syndrome characterized by widespread musculoskeletal pain, fatigue, sleep disturbance, and cognitive dysfunction ("fibro fog"). The 2010 ACR diagnostic criteria replaced the tender point examination with a widespread pain index (WPI) and symptom severity scale (SSS).
Key board points: Labs are normal (ESR, CRP, ANA, RF are all negative — this is how you distinguish it from inflammatory arthritis). Treatment is multimodal: aerobic exercise is the most evidence-based intervention, followed by cognitive behavioral therapy (CBT), and medications including duloxetine, milnacipran, and pregabalin (the only three FDA-approved agents for fibromyalgia).
Fractures: Osteoporosis and the DEXA Scan
The boards test osteoporosis screening and fracture risk assessment. DEXA scan is the gold standard for bone mineral density (BMD) measurement. Screening is recommended for all women ≥65 years and for younger postmenopausal women with risk factors (low body weight, smoking, family history, glucocorticoid use).
T-score interpretation: Normal ≥ -1.0. Osteopenia: -1.0 to -2.5. Osteoporosis ≤ -2.5. Severe osteoporosis: T-score ≤ -2.5 with a fragility fracture.
Treatment: Calcium (1000–1200 mg/day) and vitamin D (800–1000 IU/day) for all patients with osteoporosis. Bisphosphonates (alendronate, risedronate) are first-line pharmacological therapy. Key side effect: esophageal irritation — patients must take with a full glass of water and remain upright for 30–60 minutes. Atypical femur fractures and osteonecrosis of the jaw are rare but serious complications with long-term use.
The Bottom Line
MSK on the FNP boards rewards knowing the joint distribution, the inflammatory markers, and the crystal type. OA = DIP, normal labs, activity-related pain. RA = MCP/PIP, elevated inflammatory markers, morning stiffness >1 hour. Gout = first MTP, negatively birefringent needles, treat acute with NSAIDs/colchicine, prevent with allopurinol. Back pain = conservative management for 6 weeks unless red flags are present. Master these patterns and MSK becomes one of your strongest sections.
→ Explore the FNP Board Review Book — every MSK topic covered with board-focused clinical pearls.