90 patients with large, postero-superior rotator cuff tears were randomized to receive a supplement (containing arginine L-alpha-ketoglutarate, methylsulfonylmethane, hydrolyzed type I collagen and bromelain) or no supplement. Over 12 months, there was no difference between the two groups for clinical scores, rate of re-rupture, and fatty degeneration grade. However, the supplement group experienced significantly less shoulder pain than the control group at 6 months. Additionally, a larger proportion of patients in the supplement group had better repair integrity results.