Measurements of knee rotation in vivo - Development and evaluation of an external device

Abstract: The overall aim of this work was to evaluate a newly developed measurement device,
the Rottometer, for measuring knee rotation in different flexion angles with different
applied torques, in order to establish the normal range of healthy knee rotation reference
values and to study possible differences due to age and gender, as well as possible
differences between patients with habitual dislocating patella (HDP) and healthy
controls. The validity of the Rottometer was evaluated by simultaneous registrations
with roentgen stereometric analysis (RSA) (paper I). The two methods showed high
correlations concerning the total knee rotation at 90° and 60° of knee flexion angles
with 3, 6 and 9 Nm applied torques. The Rottometer was also concluded to be a reliable
measurement device concerning the one-week-apart and within day intra-tester
as well as the inter-tester reliability at 90°, 60° and 30° with 6 and 9 Nm as well as the
examiner’s apprehension of end-feel (paper II). In total, 120 knee healthy subjects (60
females and 60 males) equally distributed in four different age groups (15-30, 31-45,
46-60 and ≥ 61 years) were examined at 90°, 60° and 30° of knee flexion angles with
6 and 9 Nm applied torques as well as the examiner’s apprehension of end-feel (paper
III). No differences were found concerning the different flexion angles, between the left
and right knee or between the different age groups within the genders. However, the
females showed a 10-20 % larger range of knee rotation than the males at all different
flexion angles and applied torques. The knee rotation was also examined in 20 patients
(15 females and 5 males) with HDP (paper IV). No differences were found between
the affected and unaffected knees within the subjects. In accordance with the healthy
reference population, the female subjects showed a 10-20 % significantly larger range
of rotation than the male subjects in the HDP group, and no differences were found
between the patients affected with HDP and age matched healthy controls.