HSS researchers conducted experiments using a rat model of patellar tendon injury and repair. The investigators used a small metal frame to hold the joint in place and then used a specially designed motorized device to precisely apply loads of strain. One group of rats received a low load 50 times per day (analogous to a leg extension with no weight), another group received a moderate load 50 times per day and a third group had their joint immobilized for the entire study period. The animals were studied at four, 10, 21 and 28 days.
The researchers found that rats that had their joint immobilized had the best healing with significantly less fibrocartilage or scar tissue than rats in the other two groups. The researchers suggest the best path to recovery for patients undergoing rotator cuff surgery might be to keep patients in slings for six weeks and then start with passive motion therapy. However, studies are needed in humans to test this hypothesis and make firm clinical recommendations.