Table 1.

Traditional classification of osteoarthritis (OA)

Primary or idiopathic
Localized	Hands: e.g. nodal OA, erosive OA, first CMC joint OA
	Feet: e.g. hallux valgus, hallux rigidus, talonavicular OA
	Knee: e.g. patello-femoral syndrome, medial/lateral compartment OA
	Hip: e.g. diffuse, superior, concentric
	Spine: e.g. DISH, spondylosis, intervertebral joints, apophyseal joints
	Other: wrist, glenohumoral, acromioclavicular, temporomandibular
Generalized	Includes three or more areas listed above
Secondary
Post-traumatic	e.g. fracture, infection, joint surgery
Congenital disorders	e.g. congenital hip dislocation, chondral dysplasia
Metabolic	Calcium crystal deposition
	Haemochromatosis
	Acromegaly
	Paget's disease
	Ochronosis
Inflammatory	Any inflammatory arthritis, e.g. rheumatoid arthritis
	Septic arthritis
Other bone and jointdisorders	Avascular necrosis, neuropathic charcot joints

CMC, carpometacarpal; DISH, diffuse idiopathic skeletal hyperostosis.