Thigh muscle soreness can be caused by: taking stairs, walking, walking uphill or downhill, lifting objects, pushing objects, bicycling, doing crouching or squatting type motions, or even walking a dog that pulls. It's more likely to occur after doing an activity that you normally do not perform.
Often thigh muscles will get sore if you've walked around for a long while, or even used them a lot the previous day. It is also possible that during the middle of the night, they cramped up which would make them sore the next day.
If you were doing a new type of exercise in which you use your muscles in a different way than they are used to then would most likely be the reason. You should try massage therapy and put icy hot on your legs. The soreness should go away but if it doesn't, go see your doctor.
The most common cause of sore thigh muscles is simple overuse. Another cause may be the shoes that you are wearing. If you have been working out or alking alot take a break. If not, look at your shoes.
Well you'd need to begin with what part of the thigh, upper,lower,inner,outer?? Did you do anything such as a lot of dancing, climbing stairs, lifting heavy things? Any excessive use of the thigh muscles can strain them?