A subsequent study in 1982 on rabbit ligaments by Lui et al showed that prolotherapy might have a positive effect on mass, thickness, enthesis strength, and weight-to-length ratio of injected ligaments, as compared to controls. A different study by Klein et al in 1989 showed histological documentation of ligament proliferation in human subjects. This was in response to proliferative injections, which objectively increased the diameter of collagen fibers with an associated decrease in pain as well as an objective increase in range of motion. In another study, Ongley et al found a statistically significant reduction in ligamentous laxity 9 months after injecting the ends of collateral and cruciate ligaments of knees that had substantial ligamentous laxity as measured by a computerized knee analysis device. All of these studies found decreases in pain levels of patients involved.