Patella tendon inserts into the tibial tuberosity - the tibial tuberosity is at the epiphyseal plate
Stress from running, jumping and other movements at the same time as growth in the epiphyseal plate result in inflammation on the tibial epiphyseal plate
There are multiple small avulsion fractures - where the patella ligament pulls away tiny pieces of bone
This leads to growth of this tibial tuberosity, causing a visible lump below the knee
Initially this bump is tender due to the inflammation, but as the bone heals and the inflammation settles it becomes hard and non-tender
