At straightening a leg or foot after knee-bend, the patella rises on a place with n...

[Alexander]

At straightening a leg or foot after knee-bend, the patella rises on a place with small delay and click. nebolno, but it is very unpleasant. If to straighten a leg or foot laying or costing or standing without a load - usually click is not present.
If to rise with a load and thus strongly to press a finger above kolenkoj click too is not present. Traumas like was not. On a regular basis I play tennis.
What could it mean?

[Didkovskij A.V.]

Chronic trauma of a meniscus.