The ability of compressive forces to limit anterior tibial translation in nine subjects with anterior cruciate ligament (ACL)–deficient knees was investigated. Anterior tibial translation was measured with the knee in full extension under conditions of no compression and compression (with a load equivalent to 50% of body weight) during rest, a laxity test with an 89 N anterior force, a 30% quadriceps contraction, a 30% hamstrings contraction, and a 30% co-contraction. Arthrometer (Knee Signature System) and electromyographic data for three trials for each condition were averaged, and data were analyzed using a two-way ANOVA with repeated measures (p< 0.05). The results demonstrated that anterior tibial translation during the laxity test was limited when compressive forces were applied to the lower limb (5.23 vs. 8.08 mm). In addition, quadriceps contractions in either condition produced anterior tibial translation that was less than that obtained during the no compression laxity test (3.71 and 4.03 mm). It was concluded that knee joint compressive forces are a limiting factor in controlling anterior tibial translation and that compressive forces may be generated during what have been considered open kinetic chain activities. Knee rehabilitation programs must carefully assess the biomechanics of the exercise program in order to ensure that timely and appropriate stress is placed on the ACL and secondary restraints.