Knee rotation in healthy individuals related to age and gender.

An external device ("the Rottometer") was especially designed to measure passive knee rotation in vivo. The device had earlier been evaluated with respect to it's validity and reliability. In the present study, we evaluated knee rotation in knee-healthy individuals and studied possible age and gender related differences. Measurements of total internal-external rotation were made at 90°, 60°, and 30° of flexion using 6 and 9 N m torques, as well as the examiner's apprehension of end-feel as displacing forces. The study group constituted of 120 healthy subjects (60 females and 60 males) with no prior or present knee disorders. The sample was divided into four age groups (15-30, 31-45, 46-60, and >60 years). The results showed no differences in knee rotation between the right and left knees or between the different flexion angles. The females showed 10-20% (p < 0.01) larger knee rotation than the males at all the three flexion angles and at all the three applied torques in all age-matched groups. In all age groups in both genders, the internal rotation accounted for 40-44% and the external for 56-60% of the total internal-external knee rotation.