A sprain is an aggravation or injury to a joint. This may include stretching or tearing of the fibrous ligaments that surround the joint. These ligaments and tissues that encompass joints attach bone together and can potentially be prone to injuries. The most frequently occurring sprain is in the ankle. This joint is more susceptible to injury due to the manner in which this joint provides stability.  A strain is when a muscle or tendon is overstretched beyond the normal range of flexibility. Tears in muscles and tendons can potentially occur in the presence of a strain. Differing from ligaments, tendons are composed of fibrous tissues and join muscle to bone. Twisting or pulling these tissues can cause a strain. Some of the largest muscle groups in your body, such as your back and leg muscles, have a greater risk of overstretching solely due to their size and nature of the function.  These two injuries are similar and patients usually have a difficult time differentiating between the two. They differ in the fact that when you have a strain because it impacts the muscles and tendons, there may be muscle spasms that occur. Sprains, on the other hand, may have noticeable bruising around the affected joint.