Age 46. tore acl in 8/2013. was given physical therapy for 2 months. knee gave out (2x) in 11/2013. work with middle school students. please advise.

Consider recon.: If your knee can't not be stabilized with physical therapy and an acl brace, then it's worth considering acl reconstruction. An allograft (cadaver) is more typically used in middle-aged individuals who knee an "new" acl in order to provide long-term knee stability. If you continue to have instability episodes, then you are at risk for meniscal tears and possibly earlier or more advanced arthritis.