Can levels of antioxidants in synovial fluid predict the severity of primary knee osteoarthritis: a preliminary study

BACKGROUND Little is known about differences in amounts of antioxidants or oxidative stress at different stages of knee osteoarthritis. This study investigated the relationship between concentrations of antioxidants, iron and lipid peroxidation in synovial fluid and levels of severity of primary knee osteoarthritis. MATERIALS AND METHODS From 2011 to 2013, 23 patients (mean age, 66.7 ± 7.6 years) with primary knee osteoarthritis were recruited. Patients were divided into 2 groups based on pre-treatment knee society scores (KSS): n = 9, severe KSS ≤46; and n = 14, mild-moderate KSS >46. Synovial fluid was analyzed to determine levels of antioxidants, iron concentrations and lipid peroxidation (thiobarbituric acid reactive substances [TBARs]). Baseline data, including Kellgren- Lawrence radiographic grade, were collected for all patients. RESULTS Mean KSS was 49.1 ± 10.8. Total mean concentrations of antioxidants were 2.29 ± 1.71 ng/mL vitamin E and 0.47 ± 0.51 nmol/mL glutathione (GSH). Total mean levels of TBARs and iron were 1.20 ± 0.37 nmol/mL and 2.13 ± 0.82 μg/mL, respectively. The mean concentration of vitamin E was inversely related to severity of knee osteoarthritis (mild-moderate > severe, p = 0.006). There were no significant differences between the two groups in terms of GSH (p = 0.90), TBARs (p = 0.84) or iron levels (p = 0.27). There was a significant positive correlation between KSS and vitamin E concentration (r = 0.43, p = 0.04). No significant correlations were shown between KSS and GSH (r = -0.01, p = 0.97), TBARs (r = -0.06, p = 0.81) or iron level (r = 0.28, p = 0.20). CONCLUSION Using synovial fluid profiles, vitamin E concentration is an essential prognostic factor in primary knee osteoarthritis and may act as a basis for treatment directions. The concentration of vitamin E decreased as the clinical severity of primary knee osteoarthritis increased.