*2.3. Assessment of Synovitis Applying the Krenn Scoring System*

Forty-eight OA patients out of a cohort of 54 presented with materials sufficient for further analyses and were stratified into two groups: Nineteen HHV-7 PCR+ subjects (39.6%) and 29 HHV-7 PCR− subjects (60.4%). Seventeen HHV-7 PCR+ and 25 HHV-7 PCR− subjects presented with tissues suitable for assessing synovitis. HHV-7 PCR+ OA subjects presented with a median synovitis score of 3 (IQR 2–4), whereas HHV-7 PCR− OA subjects had a median synovitis score of 2 (IQR 1–4). The trend towards higher Krenn scores in the HHV-7 PCR+ group when compared to the HHV-7 PCR− group was confirmed (Figure 3a). There was no significant difference found in synovitis scores estimated for the HHV-7 PCR+ and HHV-7 PCR− groups (*p* = 0.483). Six (35%), 10 (59%), and 1 (6%) and 12 (48%), 10 (40%), and 3 (12%) OA patients presented without histopathologically detectable synovitis, low-grade synovitis, and high-grade synovitis in the HHV-7 PCR+ and HHV-7 PCR− study groups, respectively (Figure 3b).

**Figure 2.** Assessment of plasma levels of pro-inflammatory cytokines—tumor necrosis factor (TNF) and interleukin-6 (IL-6)—in osteoarthritis (OA) patients in both study groups, HHV-7 PCR+ and HHV-7 PCR−. Plots depict the distributions of IL-6 (**a**) and TNF (**c**) plasma levels demonstrated in OA patients in both study groups—HHV-7 PCR+ and HHV-7 PCR−. (**b**,**d**) Dot plots represent the quantified data for IL-6 (**b**) and TNF (**d**) plasma levels. (**b**) Each dot represents a single data point; blue dots represent IL-6 plasma levels assessed in the HHV-7 PCR+ group, and violet dots represent IL-6 plasma levels assessed in the HHV-7 PCR− group. (**d**) Each dot represents a single data point; blue dots represent TNF plasma levels assessed in the HHV-7 PCR+ group, and violet dots represent TNF plasma levels assessed in the HHV-7 PCR− group. The quantification limit (QL) for the assay of cytokine assessment was set as 1 pg/mL. Cytokine levels below QL (<1) were uniformly set as random values around QL/10. The right part of graph (**b**) and graph (**d**) represent data excluding values below the detection (quantification) level (w/o < 1), i.e., data without values of less than 1 (w/o < 1). W/o—without (write-off).
