Hi Telluride,
From my experience MRI's are not 100% accurate. I would first try to get to an orthopaedic specialist or a physiotherapist to clear the ligaments/meniscus in your knee. These specialists perform the knee tests more frequently then a GP so have a better feel when conducting them. From your symptoms (especially the recurrent giving way) it is possible that the medial meniscus has been torn or that the ACL damage is more than a grade I. A proper examination will determine this.