Intrinsic and extrinsic crystals and particles detected in synovial fluid
| Extrinsic crystals or particles (introduced from outside) | Intrinsic crystals or particles (formed within the joint) | |||||||
|---|---|---|---|---|---|---|---|---|
| Pathogenic | Non-pathogenic | Pathogenic | Non-pathogenic | |||||
| Corticosteroid can cause short lived inflammatory episode | From air - dust, fungal spores, (lens) tissue fibres, etc; many are birefringent | MSUM −vely birefringent needles 1–20 μm. Can form in “beachball” array | Fibrin. Hair-like strands under HP 1000X. Found in many SF | |||||
| Storage artefacts - Brushite, +vely birefringent rods 10 μm+ in “star-bursts” | CPPD +vely birefringent rods/rhomboids. 1–20 μm. Can form “beachballs” | Non-birefringent 1–20 μm “broken glass” cartilage in all SF | ||||||
| Larger (100 μm+) birefringent “silk-sheen” cartilage in damaged/arthritic joints. | ||||||||
| “Drying-out” SF gives spectacular birefringent particles resembling MSUM, CPPD, etc | BCP - submicroscopic, very weakly birefringent. Aggregates 2–80 μm visible if stained. | Meniscal fragments = silksheen + fibrillar appearance. Fragments many contain CPPD/MSUM | ||||||
| Ovoid starch granules from gloves, 10–100 μm+ birefringent weak “Maltese cross” | NB Mixed crystal populations are common | Fragments of fibrillar cruciate ligament - joint injury | ||||||
| Corticosteroids (all strongly birefringent crystals 1–40 μm) | CPPD + BCP (often) | Fragments of synovium - villi + birefringent fibrous core | ||||||
| MSUM + CPPD | Rice bodies - aggregates of synovial tissue in RA SF | |||||||
| Lederspan (1–10 μm) resembles CPPD | MSUM + cholesterol, etc | Lipid crystals - 1–30 μm ovoids. Birefringent. Bright “Maltese cross” | ||||||
| Cholesterol 5–40 μm. +vely birefringent notched plates. Lipid globules - non-birefringent (resemble air bubbles) | ||||||||