If you watch or play sports, you probably have seen an athlete hyperextend his or her knee. This injury occurs as a result of the knee bending too far backwards. When this injury occurs, usually among those playing contact or extreme sports, there is likely to be damage to soft tissue in or around the knee, swelling, and moderate to extreme pain. Following the injury, there will also probably be reduced mobility in the knee due to ligament damage, weakness, and/or swelling. At this point, it is very important to follow the RICE treatment recommendation of Rest, Icing, Compression, and Elevation. In less severe cases, recovery that includes physical therapy may take two to four weeks.