Description of fractures of tibial tuberosity in children. Type ladistal fracture, slight displacement, may extend into primary ossification center; type 1b-fragments off metaphysis, variable separation from secondary ossification center; type 2a-noncomminuted fracture at ossification center; type 2b-comminuted fracture of ossification center; type 3a-disruption of articular surface under anterior attachments of medial and/or lateral meniscus, 1 displaced fragment; type 3b-type 3a with comminuted distal fragments.