Patella fractures represent 1% of all fractures and are commonly seen after direct trauma to the bone (fall onto flexed knee, "dashboard" injury"). When to involve your consulting orthopedic surgeon is a key branch point in the management and care of these patients.

Indications for Referral to Orthopedic Surgeon:
Fractures with >2 mm of displacement
Fractures with >3 mm of fragement separation
Comminuted fractures
Disruption of extensor mechanism
Open fractures
Fractures with neurovascular deficit
Avulsion fractures of superior or inferior poles (equivalent to quadriceps/patella tendon injuries)

References:
Blount J. et al. "Patella Fractures." UpToDate. November 2016.