If you have ever picked up a heavy object suddenly and not used your legs to balance the heaviness or if you have started doing exercises after a long period and you over-exert yourself you could incur a muscle injury which does not go away and which immobilises you to some extent. 

Muscle strain is the pain that occurs when you have pulled, twisted or torn a muscle or tendon.  A tendon is the strong tissue that connects the muscle to the bone.  There are different types of muscle ... Read more