Patella pathology

Patella fracture

What is it ?

The patella, also called knee cap, may get fractured during a direct trauma: a fall on the knee, a road accident, etc. According to the type of accident and its energy, the fracture may be horizontal, vertical, or complex. It may be displaced or not (in situ).

Clinical presentation

When the patella is fractured, the pain is severe and the skin may be damaged by the trauma. If the fracture is displaced, the knee gets immediately swollen and active extension of the knee is impossible.

When to consult a specialist?

Consulting an emergency unit is necessary to get Xrays of the knee which will confirm or not the fracture. If fractured, an orthopaedic surgeon is called to discuss the best treatment.

Non surgical treatment

A conservative treatment is indicated for in situ fractures (not displaced), and for vertical fractures because mechanically they don’t interrupt the extensor mechanism of the knee. The patient has to walk with crutches for partial weight bearing, and physiotherapy will help maintining the knee range of motion and muscle tone: the exact protocol is adapted to the type of fracture and the goal is to let heal the fracture without getting stiffness of the knee.

Surgical treatment

A surgical treatment is mandatory when the fracture is transverse (horizontal) and displaced because the extensor mechanism of the knee is interrupted: this kind of fracture can’t heal by itself and needs to be fixed by an osteosynthesis using K-wires and cerclage. The fragments have to be anatomically reduced because the deep part of the patella is part of the joint, covered by cartilage. The osteosynthesis should be done in emergency, mainly if the skin is fragile or has been damaged during the accident.

Postoperative follow-up

After an osteosynthesis of the patella, the rehabilitation protocol is very progressive, in order to let the fracture heal but also to avoid knee stiffness. Most of the time, the patient walks with crutches and partial weight bearing during 6 weeks, with a range of motion of 30° for the first 2 weeks, 60° for the next 2 weeks, and 90° for the last 2 weeks. So that 6 weeks after surgery the patient should be able to bend the knee until 90° of flexion. Control XRays are done 6 weeks after surgery, and if everything is ok, the flexion and weight bearing are progressively complete.

Risks and complications

In case of conservative treatment, the risk is a displacement of the fracture and then the necessity to fix it surgically. Knee stiffness may happen if the knee is locked in extension too long.

In case of surgical treatment of the fracture (osteosynthesis), the risks and complications are:

Discomfort due to the wires which has to be removed, most of the time 1 year after the initial surgery.
Early complications after patella osteosynthesis are: skin healing problems or skin necrosis (mainly if the skin has been damaged during the accident or if the skin was under too much tension between the accident and the surgery), a displacement of the wires (may happen if the rehabilitation protocol is too agressive), infection (mainly if the skin was damaged during the accident).
Late complications after patella osteosynthesis are knee stiffness with deficit of flexion (may happen if the rehabilitation protocol is too slow), and sometimes the need to do a knee arthroscopy to release the scar tissue and get the flexion back; and patello-femoral arthritis (mainly after complex fractures because the cartilage of the patella degenerates; or if the fracture was not anatomically reduced).