Heir, Stig; Nerhus, Tor K; Røtterud, Jan H; Løken, Sverre; Ekeland, Arne; Engebretsen, Lars; Årøen, Asbjørn. Focal cartilage defects in the knee impair quality of life as much as severe osteoarthritis. American Journal of Sports Medicine 2009:doi:10.1177/0363546509352157.