• A strained hamstring is a fairly common injury suffered while competing in sports. It can impact track and field competitors along with baseball, football, basketball and soccer players. When an athlete accelerates while running, the hamstring muscle contracts and then pushes off. If the muscle is not in great shape or has been overused--a common occurrence in sports--it can get strained. You can also injure your hamstring while walking in the neighborhood or while moving around your house, but this is a bit more unusual.
  
  

Sharp Pain

• You will feel a sharp pain in the back of the leg during exercise. This is most prevalent during sprinting or when making a sudden movement. The natural reaction is to stop moving immediately and you might feel a bit of relief if you rub the muscle with your fingertips. However, once you start to walk again, you will feel a tightness in the leg and slight-to-moderate pain.
  
  

Swelling in the Leg

• When you suffer a moderate strain of the hamstring, you will notice some swelling in the back of the leg. The swelling may be on either side of the muscle strain or directly underneath. The swelling will making walking around quite uncomfortable and it will make exercise impossible. When you have swelling in the hamstring, you will need to rest the injury and ice it for 15 minutes of every waking hour for the first 6-to-12 hours after the injury.
  
  

Inability to Straighten the Knee

• A more severely strained hamstring will manifest itself with an inability to straighten your knee. This means you will not be able to bear your full weight and you will walk with a noticeable limp. In cases like this, you should use crutches in order to get around easier. Treat this injury with rest and ice. When you are resting, try to keep your leg elevated.