[Correlation of clinical joint function with histopathological features of knee joint fibrosis]

Objective: To investigate the correlation between the joint function and the histologic grading after total knee arthroplasty, to aid in the early diagnosis and prognostication of arthrofibrosis. Methods: A total of 29 patients including 22 females and 7 males were enrolled retrospectively from October 2015 to October 2020. These patients had a mean age of 63 years (range 41 to 79 years) and underwent total knee revision in Jishuitan Hospital due to joint contraction or loss of range of motion. Histologic assessment was carried out by utilizing immunohistochemistry (IHC) and the Masson staining to evaluate the fibrosis and inflammation of the samples. Results: By light microscopy, early stage arthrofibrosis showed massive proliferation of myofibroblasts and fibroblasts with SMA expression by IHC. In late stage arthrofibrosis, hyaline degeneration occured with extensive hyperplasia of fibrosis-related tissue. The arthrofibrosis samples appeared blue with Masson staining. Lymphocytes showed perivascular distribution. The arthrofibrosis tissue was mostly grade 3 (26 samples) in histologic assessment, moderate grade (25 samples) in ALVAL score, and grade 1 (23 samples) in lymphocyte grading. Fibrosis grading showed an overwhelming correlation with range of motion (ROM) of the joint. The ALVAL score was highly correlated with the WOMAC score. There was also a direct correlation between inflammatory cell infiltration and pain. The fibrosis grading joint with ALVAL score showed a good predictive value of joint function after joint replacement surgery. Conclusions: The histologic assessment score is closely correlated to the joint function with predictive values for the prognosis after joint replacement surgery.