Sample size calculation
SD
The initial sample-size calculation was based on an SD of 4.5 points for the primary outcome: subscale scores of the KNEES-ACL looseness domain. The minimal clinical important difference (MCID) was estimated to be 2.5 points. With a statistical significance (p) of 0.05 and a power of 80%, 51 patients were necessary in each group, and 102 patients were planned. Due to the loss of some patients to follow-up, a post-power sample-size calculation was made. The SD was smaller than assumed in the initial sample-size calculation, and the post-power calculation (with MCID = 2.5, p = 0.05, power = 80%, and SD = 3.3) showed that 28 patients were necessary in each group (56 patients in total).