Hi Arya,
As you are a sportsman, the
knee pain could be most likely due to
trauma. If you notice a click in a typical position of the knee, it could be a meniscal injury. If your knee locks, i.e gets stuck suddenly while extending it, again it could be related to meniscal injury or a loose body. A loose body can arise from a separated piece of
cartilage with or without bone attached to it due to previous trauma. In this case your knee may lock in a different angle every time, unlike for
meniscus where it always locks in the same angle of knee
flexion.
If your pain doesn't subside with rest, analgesics and appropriate physiotherapy, you will require an Orthopaedician's (Arthroscopy surgeon) opinion, an MRI and/or diagnostic Arthroscopy.
An MRI or diagnostic arthroscopy will reveal the problem with your knee.