20% of ACL reconstructed patients may need further surgeries.

The rate of subsequent surgery and predictors after anterior cruciate ligament reconstruction.
Hettrich, C., Dunn, W., Reinke, E., MOON group, and Spindler, K. Americna Journal of Sports Medicine, 2013; 41: 1534 – 1540.
http://ajs.sagepub.com/content/41/7/1534.abstract

Authors followed almost 1000 patients for few years after they underwent ACL reconstruction. The main aim of the study was to determine the rate at which following surgeries were required and to identify risk factors that predisposed for re – surgery among this sample. 
At six year follow – up nearly 20% of participants required subsequent surgery on the ipsilateral knee while 10% underwent surgery on the contralateral knee. On the ipsilateral knee, cartilage procedures were most commonly performed (13%), followed by ACL revision surgery (7.7%). Young age at the time of initial surgery and the use of allografts were predictors for subsequent procedure. Revision ACLR, female sex, body mass index, and surgical exposure were not significant risk factors.

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