Had a pop behind my knee cap now hurts and can't put weight on it?

Orthopedic eval: You should see an orthopedist. A pop sound and impaired ability to bear weight are suspicious for a soft tissue injury to the ligaments or tendons in the knee. In the short term, you can ice it, elevate it, compress it with an ace wrap, and take some Motrin or advil (ibuprofen).

See specialist.: See a sports medicine orthopedic knee specialist, who will start with xrays, and determine what may have happened. Use crutches if you need to.