Muscle cramps – a sudden tight, intense pain caused by a muscle locked in spasm. Muscle cramps are also recognized as an involuntary and forcibly contracted muscle that does not relax.
ACL tears – The anterior cruciate ligament; one of four major knee ligament necessary for comfortable knee movement, tears, causing major pain and causes the knee to "give out". The knee ACL can tear for a number of reasons. The anterior cruciate ligament (ACL) is a ligament involved in knee stabilization. An ACL rupture can occur when the foot is planted and the knee twists to change direction.
Ankle sprain – The ligaments that hold the ankle bones in place can easily be overstretched.
Shin splints – The tissue that attaches the muscles of your lower leg to the shin bone may be pulling away from the bone, or it may be inflamed from overuse.
Muscle strains – tears in muscle that cause pain and or loss of function.