Primary
Secondary
Trauma
- fracture
- dislocation
Infection
Tumour
Inflammatory
- RA
- seronegative (RAPE - Reiter's, AS, Psoriasis, Enteropathic)
- CT disorders (SLE, sarcoidosis, JCA)
Metabolic
- gout, pseudogout, HADD
- hemochromatosis, ochronosis
- Paget's
Developmental
- DDH, Perthe's, SUFE
Dysplasia
Vascular
- haemophilia
- AVN
Synovial
- PVNS, chondromatosis