The gross morphology of torn human anterior cruciate ligaments in unstableknees

To evaluate the presence and incidence of reattachments of torn human anter ior cruciate ligaments (ACL), we prospectively investigated 101 patients un dergoing arthroscopic ACL reconstruction to study the intra-articular morph ology of ACLs under circumstances in which functional healing had failed. R esults showed that roughly 72% of these unstable knees had reattachment of the torn ACL to the posterior cruciate ligament (PCL). Eighteen percent had no signs of ACL reattachment but only 2% of previously torn ACLs were abse nt. These results suggest that even in chronic situations in which the knee remains functionally unstable, human ACLs rarely resorb. It also suggests that tom human ACLs commonly reattach in the knee, mainly to the PCL via a process that is consistent with scarring. While the function of these reatt achments is clearly inadequate in people with unstable knees because of a c ombination of reattachment location, scar quantity, or quality, these resul ts nonetheless show that the intra-articular environment in humans often ma intains ACL stumps and it is not totally inhibitory to ACL reattachment via some biological process.