The thumbs are used to tilt the patella from side to side.
Patellar glide to mobilise the parapatellar gutters and retinaculum.
Mobilising the suprapatellar area.
Why do patellar mobilisations?
The patella is central to all movement in the knee as this bone lies within the tendon of the quadriceps muscle. If the patella is tethered down by inflammatory adhesions, the knee will not be able to properly bend and straighten.
Effectiveness of Patellofemoral Mobilisation, Stretching and Strengthening on walking Ability and Stair Climbing in Subjects with Osteoarthritic knee - A Comparative Study. Megha M, Mohanty P and Pattnaik M. Open access.
See also -
This short animation explains how the tissues around the knee may scar and lead to a decreased range of motion.