As most who follow MMA know by now, Dominick Cruz has suffered two injures to the same knee in the past year, each requiring surgical repair. Both injuries were to the anterior cruciate ligament (ACL). In a December 2012 interview with UFC Tonight, he explained that the original surgery used a cadaver ligament to replace his ruptured ACL. Cruz then had to undergo a second surgery to repair the ruptured cadaver graft. This time, his surgeon used a patella tendon graft, taken from Dominick’s patella tendon. The patella tendon graft is considered the gold-standard for ACL reconstruction. The decision to use the cadaver graft at the first surgery was probably a difficult one. Cruz had to weigh the benefit of potential faster recovery with the cadaver graft against a more reliable healing process, albeit slower recovery, with the patella tendon graft. In my MMA Injury blog post, I note that, theoretically, an athlete can return to sport-related activity sooner with the cadaver graft compared to the patella tendon graft.
From Cruz’ comments as well as those from his trainer, they believe that Dominick’s body rejected the cadaver graft. However, the cadaver tendons aren't usually at risk for rejection.