Muscle stiffness or pain

Usually worse in the early morning often with pain and stiffness

Some differential diagnoses and typical outline evidence

Normal response to strenuous exercise	Suggested by: fit healthy, unaccustomed exercise 1–2 days before.
	Confirmed by: spontaneous resolution.
Polymyalgia rheumatica	Suggested by: onset over weeks or months, stiff, painful, and tender proximal muscles. Fatigue, fever in elderly person.
	Confirmed by: ↑↑ESR. Rheumatoid factor -ve, prompt response to prednisolone, no other cause (e.g. infection on follow-up).
	Management: OHCM p424.
Rheumatoid arthritis	Suggested by: early morning stiffness. Fingers showing ‘swan neck’ or ‘boutonnière’ deformities. Thumbs show Z-deformities. MCP joints and wrists—sublux giving ulnar deviation. Knees—valgus or varus deformity and popliteal ‘Baker's’ cysts. Feet—subluxation of meta-tarsal heads with hallux valgus, clawed toes.
	Confirmed by: rheumatoid factor +ve, ↑anti-IgG autoantibody. FBC: Normochromic anaemia, ↑ESR when active.
	Management: OHCM p414.
Ankylosing spondylitis	Suggested by: onset over months or years. Stiffness and progressive loss of spinal movement. Kyphosis and spinal extension.
	Confirmed by: ‘bamboo’ spine on back X-ray and loss of sacroileal joint space. Rheumatoid factor -ve, HLA-B27 +ve.
	Management: OHCM pp410, 418.
Primary muscle disease	Suggested by: onset over weeks to years. Predominant weakness.
	Confirmed by: CPK ↑, electromyography and muscle biopsy.
	Management: OHCM p420.
Primary hypothyroidism	Suggested by: onset over weeks to months. Predominant fatigue. Also cold intolerance, depression.
	Confirmed by: ↑TSH, ↓FT4.
	Management: OHCM p306.
Early manifestation of occult malignancy	Suggested by: onset over weeks or months. Weight loss, anorexia.
	Confirmed by: subsequent appearance of malignancy, especially spinal secondary deposits.
‘Fibromyalgia’	Suggested by: variable onset—weeks to years. Diffuse pain and stiffness but no features of specific diagnosis.
	Confirmed by: no ‘subsequent’ development of features of a specific diagnosis, normal ESR, Rheumatoid factor -ve, CPK normal, TSH & FT4 normal.