What is causing sensations like crepitus in my ankles?

If its in ankle. Joint it's likely arthritis, bone spur or osteochondral defect though other things can cause it. Usually it feels like its catching on something ir you feel or hear a clicking sound.
Crepitus = creaking. Crepitus be referred to 2 kinds of descriptive term during examination: 1) a sound heard during movement and/or 2) the palpable sensation of "lack of smoothness in the joint" noted by the examiner during range of motion testing in the ankle. It can be from the bones in the ankle rubbing. It can be from swelling. It can be due to offset in the position of the joint.