Design

We focussed on controlled studies which either referred to microfracture alone or in comparison with any other surgical treatment of articular cartilage of the knee. Papers including patients who had been treated by microfracture and concomitant adjuvant procedures like ACL reconstruction or meniscus repair were accepted too, whereas papers reporting on the microfracture technique combined with the implantation of a scaffold were excluded. To achieve a best estimate of the average, to be expected treatment effect we pooled pooled before–after data of study arms using microfracture. Because cartilage studies employ various scales to measure functional improvements, we standardized treatment effects using Hedges' g. To provide clinically meaningful estimates we converted the pooled summary effect back into the respective scales by multiplying the pooled effect with pooled standard deviations of each included clinical scale.