# Tumor Necrosis Factor-Alpha (TNF-α) and Interleukin-6 (IL-6) Cytokines in the Injured Meniscus of Patients With Knee Subchondral Insufficiency Fractures: A Potential Association With Preoperative Pain

## TL;DR

This study found that higher levels of TNF-α and IL-6 in injured meniscus tissue are linked to preoperative pain in patients with knee subchondral fractures.

## Contribution

The study is the first to quantify TNF-α and IL-6 in injured meniscus tissue of patients with knee subchondral insufficiency fractures and link them to pain.

## Key findings

- TNF-α and IL-6 levels were significantly higher in injured meniscus tissue compared to healthy tissue.
- TNF-α and IL-6 levels correlated with preoperative pain scores in patients with knee subchondral fractures.

## Abstract

Background

The development of subchondral insufficiency fracture (SIF) of the knee following a medial meniscal posterior root tear (MMPRT) results in pain and limitations in daily activities. Pain in patients with SIF is associated with local chronic inflammation in the knee joint, involving the production of inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and nerve growth factor (NGF). This study aimed to quantify the levels of proinflammatory cytokines (TNF-α, IL-6, NGF) in the injured medial meniscus (IMM) tissue of patients with knee SIF and examine their potential association with preoperative pain and functional scores.

Methods

Meniscus samples were collected from 17 patients with knee SIF (mean age: 62.8 ± 2.6 years) who underwent total knee arthroplasty. The tissue samples were categorized into two groups based on the degree of injury: the IMM and the non-injured healthy lateral meniscus (HLM) as the control group. The levels of TNF-α, IL-6, and NGF in both groups were measured using an enzyme-linked immunosorbent assay (ELISA), and differences were evaluated with the Wilcoxon signed-rank test. The association between preoperative functional and pain scores and the levels of each inflammatory mediator was analyzed using Spearman’s correlation.

Results

TNF-α and IL-6 were detectable in the meniscus tissues, while NGF levels were negligible. The levels of TNF-α and IL-6 were significantly higher in the IMM group compared to the HLM group (p<0.05). Furthermore, TNF-α and IL-6 levels in the IMM group were correlated with the pain subscale of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).

Conclusions

This study demonstrated a significant increase in TNF-α and IL-6 cytokine levels in the IMM compared to the non-injured healthy meniscus. These findings suggest that inflammatory mediators within the IMM may be associated with preoperative pain in patients with SIF in the medial femoral condyle resulting from MMPRT.