High Prevalence of Abnormal MR Findings of the Distal Semimembranosus Tendon: Contributing Factors Based on Demographic, Radiographic, and MR Features

The objective of our study was to determine the prevalence of thickening and signal alteration of the distal semimembranosus (SM) tendon on knee MRI and analyze the patient factors associated with abnormal MR findings of the distal SM tendon.Knee MRI scans of 116 subjects (58 men, 58 women; mean age, 48.5 years; range, 18-79 years) who underwent knee surgery were evaluated to assess the distal SM tendons in terms of signal alteration and thickness. To determine the factors associated with MR findings of the distal SM tendon, we assessed demographic characteristics; Kellgren-Lawrence radiographic osteoarthritis grading; history of trauma; the condition of the cruciate ligaments, collateral ligaments, and menisci; and whether there were cystic lesions around the SM tendon. In addition, 55 control subjects with normal knee MRI findings based on the electronic MRI patient database who had anterior knee pain and did not undergo surgery were enrolled.Abnormal thickening of the distal SM tendon was found in 52.6% of knees and signal alteration in 44.8%. Univariate analysis revealed significant associations between abnormal thickening and age, body mass index, history of trauma, osteoarthritis, medial collateral ligament (MCL) thickening, and anterior cruciate ligament (ACL) tear. As for signal alteration, univariate analysis showed that age, body mass index, osteoarthritis, and MCL thickening were statistically significant factors. Multivariate binary logistic regression analyses showed that osteoarthritis and MCL thickening were the strong independent predictors in thickening and signal alteration of the distal SM tendon.Signal alteration and abnormal thickening of the distal SM tendon on MRI are frequently seen in daily practice. These MR findings are strongly associated with osteoarthritis and MCL thickening.