Effect size for different surgical interventions measured by KOOS. KOOS effect sizes 6 months following surgical knee interventions. Effect size was defined as mean score change divided by the pre-operative standard deviation. The data from total knee replacement  (n = 105, mean age 71.3 years) and anterior cruciate ligament reconstruction  (n = 21, mean age 32 years) are previously published. The data from tibial osteotomy concerns 50 patients (mean age 54 years) undergoing hemicallotasis osteotomy (W-Dahl A, Lund University, personal communication 2001). The data from cartilage repair concerns 50 patients (mean age 34 years) undergoing autologus cartilage transplant (Olsson M, University of Gothenburg, personal communication 2002). The data for meniscectomy concern 66 patients (mean age 44 years) undergoing arthroscopic partial meniscectomy (Roos E, Lund University, personal communication 2003). Placebo or sham treatment results have not been subtracted to generate effect sizes. It should be noted that the effect size displayed here will be influenced by the preoperative within-group variation of the score dimension measured. This may vary between the different study groups. All data are published with permission from the authors.