AbstractIn an experimental study various synthetic augmentation devices for knee ligament surgery were tested in a servo‐mechanical universal tensile testing machine under uniaxial loading. Two tests were done to elucidate the mechanical behaviour: stress relaxation and stress‐strain relationship. Regarding the point of failure or rupture, the strongest ligament was the Trevira et 1800 N, followed by the 8‐mm‐wide Kennedy LAD at 1720 N. At a working load of 500 N the Gore‐tex band, the Trevira, and the Kennedy‐LAD stretched by between 2% and 3%. For synthetic augmentation in repair of proximally ruptured anterior cruciate ligaments we recommend a synthetic ligament that reaches failure point at a load of more than 1000 N with an alteration in length of less than 5%. Otherwise, stress protection of the biological reconstruction in full extension will be impossible. The requisite criteria were fulfilled by the Trevira, Kennedy‐LAD and Gore‐tex synthetic ligaments.