Fractures of patella, despite its small size may lead to profound pain and impairment of the extensor mechanism of the lower extremity (1)
Patella fractures can be due to either:
- indirect force - typically results in transverse fractures
- direct force - results in comminution, articular injury, anterior soft tissue damage and thus open injury (1).
There are three different types of fracture of the patella that may occur:
- an undisplaced fracture of the patella - likely to be the result of a direct blow
- a 'stellate' (comminuted) fracture - likely to be due to a direct blow to the front of the knee or a fall
- transverse fracture with a gap between the fragments - may occur if there is forced, passive flexion of the knee joint whilst the patient has his quadriceps muscles - knee joint extenders - contracted.
In the first two types, the extensor mechanism of the knee is left intact. In the third type, injury the extensor mechanism is completely disrupted and active knee extension is impossible.
- combination of fracture patterns can be commonly seen as well e.g. - a direct impact which is accompanied by knee flexion and quadriceps contraction may result in marked fragment displacement and soft tissue injury (1).