What could cause a tingling sensation in inside of left knee cap when sitting and bending knee? i dont feel it when i stand. there is no pain. and if i squeeze my left calf i can feel the tingling?

Possibility of Neuropathy , which on certain positions gets aggravated. Usually these are posture related , needs to be evaluated by a Doctor, you may need some Nerve conduction studies, also X rays of your lower back , even an MRI to see if any of the nerves from the lower back is getting pinched by a Disc.

Have you injured your left leg? Tingling is a sign of damage to a nerve. Damage to the femoral nerve in the leg can cause tingling in the knee. A neurologist can evaluate you for nerve damage and would most likely have an EMG performed as part of the examination. if not a nerve issue, an orthopedic surgeon can evaluate you for presence and type of knee pathology.