Background. Injuries of the knee joint with ACL tears cause instability of the knee. Surgical reconstruction is indicated for young, active people with functional instability of the knee, and not merely a tear in the ACL. The term "young people" is relative: even 50-year old men with no degenerative changes in the knee joint can be qualified for surgery. After surgical reconstruction intensive rehabilitation is required to restore static and dynamic proprioception of the knee. Material and methods. We examined 15 patients (a preliminary group) who underwent ACL reconstruction using the Bone-Patellar Tendon-Bone (BPTB) technique. One uear after surgery the patients were evaluated using the International Knee Documentation Committee (IKDC) knee rating scale and the Quality of Life scale of the American Academy of Orthopedic Surgeons, Council of Musculoskeletal Specialty Societies. Gait analysis was performed using an Ultraflex system (ground reaction forces and goniometry). A modified Romberg's test was added in order to examine proprioception. Results. The results from the IKDC scale gave 12 poor results and 3 good. The Quality of Life scale shows disappointment in 9 patients, satisfaction in 4 and indifference in 2. The modified Romberg's test revealed significantly decreased control of the operated joint. Gait analysis revealed a decreased range of motion in the operation joint on the sagittal plane. Conclusions. Surgical treatment cannot give satisfactory results without intensive and comprehensive rehabilitation. Physiotherapeutic goals should be not only recovery of a full range of motion and muscle strength, but also neuromuscular and proprioceptional reeducation.