Correlation Between Grading Of MRI-determined Thickness Of Synovitis And Pathological Scores Of Synovital Membrane With Knee Joint Function Scores And Pain Scores In Patients With End-stage Osteoarthritis

Knee osteoarthritis (OA) is caused by a synergy of mechanical and biological factors, and involves not only lesion of a single cartilage but also of the entire joint. Both the synovium and subchondral bone are involved in the pathological process. Furthermore, inflammation plays a key role in promoting the progression of OA and degradation of the cascade reactions. Accurate assessment of synovitis helps in the clinical staging of knee OA and in developing a stepwise therapeutic regimen.Currently, three main methods (magnetic resonance imaging [MRI], arthroscopy, and tissue biopsy) are used to examine the synovial thickness and the inflammation level in patients with OA. Each method has its advantages and limitations. For example, arthroscopy has more intuitive and visualized features, but can cause invasion and has lower repeatability. MRI is a noninvasive method and can investigate the entire synovium of the joint, but it has limited access. It is confirmed that a good consistency can be found in the three methods. The most direct evidence for the correlation is reflected in the scope of the synovial hyperplasia on MR images and the manifestation of synovitis under an arthroscope. MRI can detect early synovial changes with a high sensitivity. Furthermore, MRI can show the synovial hyperplasia of gonitis even without clinical manifestations. Thus, MRI is currently considered the gold standard for synovium imaging. The pathological assessment of the synovium is relatively simple and has strong operability, which helps in the clinical diagnosis of OA, OA staging, and prediction of OA progress.The MRI-determined thickness of the synovial membrane can successfully assess the severity of synovitis in patients with knee OA. The consensus is that the synovitis score is related to the pathological score. However, currently, there are disagreements about the correlation between synovitis with arthralgia and functional scores. One study showed that synovitis was related to pain changes, whereas another study indicated that synovitis was not related to pain. The correlation between the synovial pathology and the pain and function scores is also controversial.To further define the role and significance of MRI-determined synovial thickness and the pathological characteristics of the synovial membrane in patients with knee OA in assessing OA progress,31patients with end-stage knee OA were selected to analyze whether there is a correlation between the grades of MRI-determined thickness of the synovial membrane, pathological scores, knee joint pain scores, and function scores in our study, and to further investigate whether the severity of synovitis can be used in the criteria for the indications of knee replacement. Purpose:Synovitis is common in knee osteoarthritis. However, the relation between the grading of magnetic resonance imaging (MRI)-determined thickness of synovitis, pathological scores of the synovial membrane, and visual analog scale (VAS) pain score and the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index is still controversial. The aim of this study was to further investigate if MRI findings or the microscopic characteristics of synovitis could be used as criteria for the indications of knee replacement. Methods:Thirty-one patients with end-stage knee osteoarthritis (OA) were selected and received the following examinations:(a) noninvasive MRI evaluation for grading the synovial thickness of the investigated sites (i.e., medial and lateral parapatellar recesses, and medial and lateral suprapatellar pouches; synovitis was categorized into grades0-3on the basis of the thickness);(b) hematoxylin and eosin (HE) staining and pathological score grading of samples from the synovial membrane at each observed site;(c) determination of knee-joint pain scores (VAS pain score) and functional scores (WOMAC) before total knee arthroplasty (TKA). Pearson’s linear test or Spearman rank test was used to analyze the correlation between synovial thickness, pathological scores and WOMAC OA index, and VAS pain score. Results:Statistical analysis revealed no significant differences in MRI synovial thickening grade across the different regions of the knee. And the mean pathological score of the different regions were also revealed no significant differences. So does the mean pathological parameter scores (F=2.146,P=0.123). The grade of MRI-determined thickness of synovitis in patients with end-stage knee OA was positively correlated with the pathological scores (rs=0.81,0.56,0.59, and0.52respectively; P<0.01) and the three pathological parameters (rs=0.4,0.47, and0.36, respectively; P<0.05). No correlation existed between the grades of MRI-determined thickness for synovitis and knee joint function scores with pain score (rs=0.17, P=0.35; rs=0.32, P=0.08, respectively), as well as between the pathological scores and the above factors (rs=0.29, P=0.11; rs=-0.06, P=0.74, respectively),so does the mean pathological parameter scores (rs=0.05, P>0.05; rs=0.14, P>0.05, respectively). Conclusion:There was no correlation between the grades of MRI-determined thickness of synovitis, pathological scores, and the subjective grades in patients with end-stage knee OA. The grades of MRI-determined thickness and the pathological scores cannot been used as criteria for knee joint replacement indications. Further study on the relation between MRI, microscopic characteristics of synovitis, and VAS and WOMAC scores is still warranted.