Knee and shoulder joints are recipients of the greatest amounts of stress placed upon any joints in your body, particularly in sports. Your knee gains most of its stability through ligaments and tendons, which connect bone to bone and muscle to bone. Injury can occur if your knee is subjected to greater stress than it's designed to handle. One of the most common knee injuries is a ligament sprain, which usually occurs when you plant your foot and twist. The anterior cruciate (KRUE-she-ate) ligament, or ACL (A-C-L), is considered the key guide wire in your knee and is one of the most common ligaments injured. It's not uncommon to hear a 'pop' as the injury occurs and there are instant feelings of instability or giving way. Cartilage, which acts as a shock absorber between the two bones connecting your knee, can also tear (tehr), causing pain and discomfort. With most sprains, your knee can heal with rest, ice, and exercise, but surgery may be required to heal damage to ligaments or cartilage. Like your knees, the shoulders are used in everyday activities and subject to many types of injuries. Some of the most common injuries to your shoulder are muscle strains, capsule tears (tehrs), bursitis (ber-SIGH-tis) and tendonitis (ten-dih-NYE-this) and separated and dislocated shoulders. Muscle strains can be attributed to faulty mechanics or overuse, while bursitis or tendonitis are chronic conditions that can occur from overuse, poor posture, muscular imbalance, and other causes. Separated and dislocated shoulders may require a proper rehabilitation program to heal correctly.