Introduction. In the 1970s and 1980s, the rehabilitation program after anterior cruciate ligament (ACL) reconstruction recommended that patients’ limbs should be immobilized from 2 to 4 weeks. After such a period, the patient would be wearing a stabilizer until the end of the 3rd or 4th month. The limb could not be strained for 6 weeks. Aim. The aim of this paper was to present a Norwegian rehabilitation protocol after ACL injury and to show its effectiveness through examining the muscle strength on the Biodex system 3 Pro after periods of 3 and 6 months following the reconstruction. Materials and methods. The rehabilitation protocol described in Physical Therapy No. 6 Vol. 87 was employed. 18 patients (5 women and 13 men) were rehabilitated after reconstruction with semitendinosus and gracilis tendon grafts. All patients were rehabilitated from 2008 to 2009 in the Stefan Bołoczko Motor Rehabilitation Center, located in the Olsztyn Higher Education Institution. After periods of 3 and 6 months, these patients underwent isokinetic muscle strength test. The Biodex system 3 Pro was used. Results and Discussion. Patients rehabilitated according to the described protocol reached an average value of muscle strength between an operated limb and a healthy one amounting to 16.8% for extensors and 11.3% for flexors after 3 months following ACL reconstruction. This result allowed them to start a running program. After 6 months, the average value of muscle strength for extensors was 6.15% and 4.45% for flexors. This also allowed these patients to practice appropriate sport disciplines. Conclusions. The rehabilitation performed according to the Norwegian protocol speeds up regeneration of muscle strength after periods of 3 and 6 months, which enhances the patients’ quicker recoveries with respect to their daily functioning and physical activities. The aforementioned rehabilitation procedure does not have any negative effects, provided that patient, physician and physiotherapist cooperate closely with each other.