Tuberculum intercondylare tibiae tertium as a predictive factor for anterior cruciate ligament injury.

The aim of this study was to assess the presence of tuberculum intercondylare tibiae tertium, also known as Parsons' knob, and to determine its prominence. Knee radiographs of 171 patients operated on for anterior cruciate ligament injury were examined. The control group included 120 sex- and age-matched patients who underwent orthopaedic examination for knee pain, in whom anterior cruciate ligament injury was ruled out. Knee radiographs revealed the presence of tuberculum intercondylare tibiae tertium in 55 (32.2%) and 16 (13.3%) patients from the study and control groups, respectively. The between-group difference was statistically significant. The authors developed their own method of tuberculum intercondylare tibiae tertium measurement using proportional coefficients based on the length of the tibial plateau to compare the values of the tuberculum intercondylare tibiae tertium. The results showed tuberculum intercondylare tibiae tertium to be not only more common but also more pronounced, especially in height, in the patients with anterior cruciate ligament lesions.