MSK-20 · Rheumatoid Arthritis, Osteoarthritis, and Crystal Arthropathies

Rheumatoid Arthritis, Osteoarthritis, and Crystal Arthropathies. Part of the Musculoskeletal series of the Reflex PM&R Board Review podcast. Audio corrections: (1) In the audio: the swan neck deformity is characterized by hyperextension at the PIP joint paired with flexion at the DIP joint — Correct: Swan neck is a three-joint pattern: MCP flexion, PIP hyperextension, and DIP flexion. The driver is MCP synovitis with intrinsic (lumbrical and interosseous) tightness pulling the lateral bands dorsal to the PIP axis; boutonniere is the mirror image and adds compensatory MCP hyperextension. (2) In the audio: the four H diseases, hyperparathyroidism, hemochromatosis, hypomagnesemia, and hypothyroidism — Correct: The fourth core H is hypophosphatasia (congenitally low alkaline phosphatase), not hypothyroidism, and not the near-homograph hypophosphatemia. Hypothyroidism is a weaker traditional association, and amyloidosis is a real association that sits outside the mnemonic. (3) In the audio: Hyaluronic acid visco-supplementation is also used as an intraarticular injection, though its actual clinical efficacy remains heavily debated in the literature — Correct: Hyaluronic acid is conditionally recommended against for knee osteoarthritis under the 2019 rheumatology guideline; the benefit over placebo is minimal and inconsistent. Acetaminophen in the same ladder is only conditionally recommended, not an equal escalation step beside oral NSAIDs. The written chapter is correct. Full correction register: https://www.reflexpmr.com/errata. The full companion chapter and a linked board-style Q-bank set for this topic are at https://www.reflexpmr.com/read/MSK-20.