Comparisons and analysis of cut-off points of patient-reported and performance-based functions in early stages of knee osteoarthritis: A cross-sectional study

Objective

The primary aim was to compare patient-reported and performance-based functions of early stages of knee osteoarthritis (OA) according to radiographic grades. The secondary purpose was to determine the ability of physical function assessments to discriminate the stages.

Methods

Ninety-five symptomatic knee OA patients (median age = 51 [45–58] years; 65.3 % women) were classified as pre-radiographic (grade 0, n = 19), early (grade 1, n = 38), and mild (grade 2, n = 38) according to the Kellgren-Lawrence. The Knee Injury and Osteoarthritis Outcome Score (KOOS), Visual Analog Scale (VAS), 6-Minute Walk Test (6-MWT), Stair Climb Test (SCT), and Single-Limb Mini Squat Test (SLMS) were used for evaluations. Statistical analyses were performed with One-Way ANOVA, Kruskal Wallis, and ROC analyses.

Results

Pre-radiographic, early, and mild knee OA showed no differences in VAS and KOOS-pain, daily living activities, and quality of life (p > 0.05). The mild group had lower KOOS-sports and recreational activity scores than the pre-radiographic group, had the shortest 6-MWT distance, longest SCT time, and lowest SLMS repetitions. The early group had fewer SLMS repetitions than the pre-radiographic group. The SLMS Test, SCT and 6-MWT values with the best balance of sensitivity and specificity for discriminating early knee OA were 15 repetitions, 11.75 s and 483 m, respectively (area under the curve: 0.816, 0.753 and 0.798 respectively).

Conclusion

No differences were observed for patient-reported functions except KOOS-sport and recreational activities; however, performance-based physical functions differed between radiographic stages. The cut-off results of the performance-based functions may be useful for clinical screening and follow-ups in early knee OA.