I m having a very sharp pain in my legs my thigh is so tight and its so painful thats it hard to move. pain behind knee! wtd? im 145lbs 5 0 inches

Will need evaluation: Maybe a thigh muscle problem. Sometimes the knee can have a Baker cyst and can leak fluid into the thigh. It’s hard to say for sure if this is your problem. Would suggest you see a rheumatologist.

Nerve: The combination of pain radiating down the leg and numbness is consistent with a nerve impingement from a bulging disc in your lower spine. A lesser cause is primary nerve inflammation(neuritis). A neurologist is best qualified to evaluate and advise you. A spine MRI may be ordered.