Affiliations: [a] Department of Physical Education and Sports Science,
Democritus University of Thrace, 69100 Komotini, Greece | [b] Department of Physical Education and Sports Science,
University of Athens, 17237 Athens, Greece | [c] Orthopedic Department, General Hospital of Xanthi,
68100 Xanthi, Greece
Note: [] Address for correspondence: Paraskevi Malliou, PhD, Assistant
Professor, Department of Physical Education and Sports Science, Democritus
University of Thrace, 69100 Komotini, Greece. Tel.: +30 25310 39662; Fax: +30
25310 39662; E-mail: pmalliou@phyed.duth.gr
Abstract: The purpose of this study was to determine the reproducibility of
measures for maximum knee extensor and flexor concentric strength on an
isokinetic dynamometer in individuals with mild and moderate osteoarthritis of
the knee. Twenty eight female patients with 1st (n=14) and 3rd (n=14) grade
unilateral knee OA volunteered for the study. Peak muscle torque of the knee
extensors and flexors was measured using an isokinetic dynamometer at angular
velocities of 90, 120 and 150°/s. Test-retest reproducibility of
maximal isokinetic torque was evaluated using intraclass correlation
coefficient (ICC). Absolute reproducibility was assessed using Bland-Altman
analysis, the standard error of measurement (SEM and SEM%) and the smallest
real differences (SRD & SRD%). Inter-session relative reproducibility
was found to be high in extensor and flexor muscles of individuals with mild
OA, with the ICCs values ranging from 0.89 to 0.92 for the concentric knee
extension and from 0.90 to 0.93 for the concentric knee flexion, while in the
group of individuals with moderate knee OA the same values varied from 0.79 to
0.91 and from 0.75 to 0.93 for the concentric knee extension and flexion,
respectively. The Bland-Altman analyses support the findings of high relative
reproducibility for the two groups of patients in almost all measurements,
except for the extension at 120 and 90°/s and the flexion at
150°/s conducted by the individuals with moderate OA. SEM and relative
SEM values ranged from 6.7 to 9.4 Nm and from 14.4% to 21.5%Nm for the
group with mild OA and from 4.4 to 7.7 Nm and from 14.6% to 21.8%Nm for
the group with moderate OA, respectively. SRD and SRD% values across all
movement speeds for both knee flexors and extensors ranged from 18.6 to 26.1 Nm
and from 39.9% to 59.6%Nm for the mild OA group, respectively, while the
same values for the moderate OA group ranged from 12.2 to 21.3 Nm and from
40.5% to 56.8%Nm, respectively. These results indicate that measurements
of isokinetic performance at velocities of 90, 120 and 150°/s provide
acceptable reproducibility for evaluation of knee strength in individuals with
mild OA of the knee. On the other hand, with regard to knee muscles isokinetic
performance, testing of individuals with moderate OA should be conducted during
periods of time when the symptoms of the disease subside.
