Lateral meniscal tears and their evolution in acute injuries of the anterior cruciate ligament of the knee. Arthroscopic analysis.

Arthroscopic diagnosis was used to determine the incidence of the most frequent injuries to the knee's internal structures associated with ACL tear as well as ones without ACL tear. The most frequent finding associated with a recent ACL tear was the LM tear (72.7%). There is a statistically significant incidence of recent LM tear in knees with a recent ACL tear compared with recently injured knees without an ACL tear (P < 0.001). A statistically significant incidence of longitudinal LM tear was found in knees with a recent ACL tear compared with recently injured knees without an ACL tear (P < 0.001). Longitudinal tears were present in 63.6% of the knees with a recent ACL tear or in 87.5% of all knees with a recent LM tear. No statistically significant difference was found in the incidence of LM tear in the knees with a recent ACL tear compared to the incidence of LM tear in knees with an old ACL tear (P > 0.05). The posterior horn was most frequently injured (71.5% vs 64.0%). A significant difference between the findings in the various patient groups studied supports the hypothesis that longitudinal LM tears in an ACL-deficient knee do not involve secondary meniscal pathology but that their onset derives from a primary recent injury. Most probably, the recent LM lesion does not evolve in meniscal length and depth. This hypothesis needs thorough investigation.