Roos EM, Roos HP, Lohmander LS, Ekdahl C, Beynnon BD. Knee Injury and Osteoarthritis Outcome Score (KOOS) --development of a self-administered outcome measure. J Orthop Sports Phys Ther. 1998 Aug;28(2):88-96 

Vaquero J, Longo UG, Forriol F, Martinelli N, Vethencourt R, Denaro V. Reliability, validity and responsiveness of the Spanish version of the Knee Injury and Osteoarthritis Outcome Score (KOOS) in patients with chondral lesion of the knee. Knee Surg Sports Traumatol Arthrosc. 2014 Jan;22(1):104-8