Degenerative, Inflammatory, and Metabolic Musculoskeletal Conditions
Osteoarthritis versus rheumatoid arthritis
Osteoarthritis is mechanical: weight-bearing joints, pain worse with use and better with rest, morning stiffness under 30 minutes, Heberden (DIP) and Bouchard (PIP) nodes, asymmetric, no systemic features; radiographs show joint-space narrowing, osteophytes, subchondral sclerosis, and cysts. Rheumatoid arthritis is inflammatory and systemic: symmetric small-joint involvement (MCP, PIP, wrists), morning stiffness over one hour, improvement with use, ulnar deviation, swan-neck and boutonnière deformities, nodules, fatigue, and extra-articular disease. Rheumatoid factor supports the diagnosis, but anti-CCP is more specific.
Drug teaching that gets tested
Methotrexate is a weekly DMARD, not a daily drug, and is paired with folic acid; monitor CBC, liver enzymes, and renal function. Biologics raise infection and tuberculosis risk - screen before starting and teach signs of infection. NSAIDs and corticosteroids relieve symptoms but do not halt joint destruction in rheumatoid arthritis. Osteoarthritis has no disease-modifying drug; arthroplasty is offered for pain and function.
Metabolic bone disease
Osteoporosis: normal labs, low bone density, fragility fracture; bisphosphonates are taken upright with water and the patient stays upright 30 minutes. Teriparatide is anabolic and avoided in malignancy. Osteomalacia: low vitamin D, low phosphate, high alkaline phosphatase, Looser zones, proximal weakness. Paget disease: high alkaline phosphatase with normal calcium and phosphorus, bone enlargement, bowing, hearing loss, and small risk of sarcomatous change.
Rule of thumb
Crystals settle the acute joint: needle-shaped and negatively birefringent means gout; rhomboid and positively birefringent means pseudogout (CPPD).