Ask a PT Response: "If you are sticking with Pilates based exerices (mat, reformer, etc) you should be OK. The ACL assists with preventing translation of the femur over the tibia anteriorly. You may want to check with your client to see if he/she sustained a partial tear or complete tear of the ACL. Therefore, exercises which may involve pivoting, cutting, and rotation may give a patient with an ACL tear some problems. If you are having your client utilize other machines, the http://www.bigfitness.com/quphselegexw.html - leg extension machine should not be utilized as this machine will put alot of stress on the knee."