A method of promoting regeneration of surface cartilage of a joint includes the steps of covering the area to be treated with a patch which includes a sheet of collagen membrane material. The collagen membrane material has at least one barrier layer to prevent passage of cells therethrough. The collagen membrane further includes a matrix layer predominantly of collagen II having an open sponge-like texture. The patch is fixed over the area to be treated, and the area is allowed to regenerate cartilage.