Representative micrographs of slit wounds made with a modified Beaver blade in the center of the MCL and ACL seven days earlier in a canine knee. Note that the MCL wound is filled with a provisional scaffolding material containing high amounts of multiple growth factors important in tissue healing (here, immunohistochemistry for FGF-2 where red is a positive stain). In the ACL wound, however, the defect remains unfilled, even after seven days. (Adapted with permission from Steiner, ME, Murray, M.M. and Rodeo, S.A. Strategies to Improve Anterior Cruciate Ligament Healing and Graft Placement, American Journal of Sports Medicine, 2008, 36(10), pages 176–8923.)