Background/Purpose:

Although osteoarthritis (OA) is commonly described as a non-inflammatory joint disease, synovial inflammation is increasingly recognized as contributing to the symptoms and progression of OA.

The aim of this study is the evaluation of synovial inflammation degree by  macroscopic and histological findings in patients with knee OA.

Methods:

Samples of synovial tissue were obtained from 22 patients with knee OA.  The arthroscopy was performed under local anesthesia with sedation. During arthroscopy the joint is distended by infusion of sterile saline with a motorized suction shaver. Each patient underwent a systematic examination of the synovium from the suprapatellar poach, patellofemoral joint, lateral recesses and medial and lateral compartments of femoro-tibial joint. The arthroscopic findings were reflected in a data collection sheet. Biopsies of synovium were obtained from directly visualized areas with biopsy forceps. For macroscopic assessment of the synovial membrane we used a macroscopic semiquantitative scoring system based on the existence of vascularization and proliferation. Vascularization was assessed by the absence or presence of hyperemia and increased vascularity (score of 0 or 1). Synovial proliferation scored 0, 1 or 2 depending on the presence or absence of granularity and villous hypertrophy. The total score of the two components ranged from 0-4. The histological samples were processed with hematoxylin-eosin for histological semiquantitative scoring of synovitis. This scale was based on enlargement of the lining cell layer (0-3 points), density of the residents cells (0-3) and inflamatory infiltrate (0-3). According to the score the findings were classified in the absence of synovitis (0-1), low-grade synovitis (2-4) or high-grade synovitis (5-9 points).

Results:

Samples were obtained from 20 of the 22 arthroscopies performed.  Macroscopically, we observed pluricompartimental synovitis in 7 patients and localized in 6. In one patient, synovitis adjacent to chondral injury of the femoral condyle was found. Microcrystals were found in the synovium of 4 patients not previously diagnosed of microcrystalline arthropathy. Regarding the total score of macroscopic semiquantitative analysis, 10 patients (50%) scored between 2 and 4. No patient had scores of 0. Histological assessment was performed in 17 of the 20 patients, excluding those cases with presence of microcrystals or insufficient material. The microscopic semiquantitative score showed low-grade synovitis in 7 patients (41%) and high grade in 9 (53%). Only in one of the samples histological synovitis was not evidenced.

 Conclusion:

The frequency of synovitis in patients with osteoarthritis and synovial effusion assessed by macroscopic or histological criteria is high. Arthroscopic assessment of synovitis shows a good correlation between macroscopic dimension and microscopic histological analysis.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/evaluation-of-synovial-inflammation-assessed-by-macroscopic-and-histological-criteria-in-patients-with-knee-osteoarthritis/