Introduction
Draft proposal for classification criteria for early osteoarthritis of the knee (EKOA) according to Luyten et al. contains 1)Pain, symptoms/signs, self-reported function, and quality of life using tools such as Knee Injury and Osteoarthritis Outcome score (KOOS): scoring =85% in at least 2 out of these 4 categories; 2) Clinical examination: at least 1 present out of joint line tenderness or crepitus; 3) Knee radiographs: Kellgren & Lawrence (KL) grade of 0 or 1. Magnetic resonance imaging (MRI) and arthroscopic findings were not included as a criteria, because it’s not suitable to identify or define EKOA in routine clinical practice or primary care. Therefore, we focused on ultrasound, which is low-cost and easy to evaluate. We found several ultrasonographic findings characteristic of EKOA in our daily practice and scored each of them to develop novel ultrasonographic classification of EKOA. The purpose of this study was to investigate the ultrasound classification of EKOA and its association with KOOS symptoms and pain. We hypothesized that novel ultrasonographic classification of EKOA score would negatively correlate with the clinical knee score.
Methods
This prospective, multicenter clinical trial included patients with knee joint pain between January 2018 and April 2024 diagnosed with early knee OA based on the diagnostic criteria of Luyten et al. We targeted 241 patients who underwent MRI. Among them, 80 patients ( 31 male, 49 female, the average age was 58.0±11.7 years old) were randomly selected to investigate the association between ultrasonographic classification of EKOA and KOOS symptoms and pain. Ultrasonographic classification of EKOA. Total 12 points. For B mode: 2 points: joint effusion, medial meniscus extrusion>3mm, 1 point: Synovial hypertrophy of the suprapatellar bursa, medial meniscus degenerative tear. For doppler mode: 2 points: Blood signal flow into the femur, Blood signal flow into the tibia. 1 point: Blood signal flow at around the MCL bursa and Infra patellar bursa.
Results
The mean value of ultrasonographic classification of EKOA was 4.3±2.7. The mean value of KOOS symptoms and KOOS pain was 65.8 ± 19.3 and 60.0 ± 19.5, respectively. Ultrasonographic classification of EKOA showed negative correlation with KOOS symptoms (r=-0.43701) and weak negative correlation with KOOS pain(r=-0.33133). An ultrasound score of 8 or more points is associated with a higher rate of surgical treatment.
Conclusion
The US assessment took about only 5 minutes and was found to be not only easy to perform, but also associated with KOOS scores. Ultrasound will be the first-line examination for EKOA in the future.