MMP13 and rotator cuff syndrome: Indeed, recent studies reported an overexpression of MMP‐1 and MMP‐13 genes, involving cell‐mediated tendon degeneration, in the torn supraspinatus tendon and synovial fluid.8, 14 Shindle et al.3reported that IL‐1β, IL‐6, COX‐2, MMP‐9, and vascular endothelial growth factor (VEGF) were overexpressed in the synovium of patients with a rotator cuff tear and suggested that chronic GHJ synovitis may be associated with rotator cuff tears.