- Negatively birefringent needle-shaped
- Crystals of monosodium urate.
- 40-50 yrs (men), > 60 yrs (women).
- Any joint
- Hallux MTP is involved in over 50% of first attacks.The white count on arthrocentesis can be v high.
Hydroxyapatite crystal arthritis:
- Calcific periarthritis.
- Attacks precipitated by mild trauma or intercurrent infection.
- Associated with scleroderma, hyperparathyroidism, dermatomyositis, inflammatory joint disease, and OA.
Oxalate and lipid crystals can both cause a crystal arthropathy.
- Positively birefringent rhomboidal crystals of
- Calcium pyrophosphate dihydrate.
- 60s to 70s, (F>M).
- Most common cause of acute arthropathy in the elderly
- Classically knees
- Predisposing factors include haemochromatosis, hyperparathyroidism, hypomagnesaemia, hypophosphatasia, Wilson’s disease, gout and ochronosis.
- Triggers include trauma, intercurrent ilnness, joint aspiration and blood / fluid infusion.