Hip arthritis is a progressive degenerative joint disease.  It can have primary or secondary causes. 

Primary causes:  Idiopathic, genetic and environmental (activities and weight)

Secondary causes: Inflammatory arthropathies, osteoarthritis, developmental dysplasia of the hip, femoroacetabular impingement, slipped capital femoral epiphysis and avascular necrosis.

Treatment depends on the cause and severity of the arthritis.  It consists of conservative treatment and surgery.