The kneecap (patella) is part of the extensor apparatus of the knee. At the level of the knee joint, it forms a deflection of the extensor muscles to the lower leg. It therefore plays a key role in the active extension of the knee joint.
The patella prevents the tendon of the thigh extensor muscles from rubbing directly on the knee joint. It slides on a corresponding groove in the thigh bone.
The mechanism of injury in a patella fracture is usually a fall onto the kneecap or a severe impact trauma.
A patella fracture is accompanied by severe pain on the front of the knee joint and directly above the kneecap.
There is usually also significant swelling of the knee joint. It is typical that the lower leg cannot be actively extended or the knee joint cannot be held extended.
A clear diagnosis can be made using X-rays.
The knee joint. The patella is shown here on the right under the white muscle cords © Axel Kock | AdobeStock
The treatment depends on
Undisplaced stable fractures can generally be treated conservatively.
Surgical treatment is indicated for dislocated unstable fractures. Splinting and immobilization of the affected knee joint is always necessary. An increased risk of a blood clot(thrombosis) requires the prophylactic administration of antithrombotic medication.
During surgical treatment, the fracture fragments are held in place with drill wires or screws. A special tension bandage absorbs the tensile forces (cerclage).
After the patella fracture has healed, it is usually necessary to remove the implants in a further operation.
The knee joint is primarily immobilized using special splints. The leg should not be loaded and active stretching should be avoided.
Physiotherapeutic follow-up treatment can be started at an early stage.
Mobilization after surgical treatment depends on the extent of the injury and the surgical procedure. Osteosyntheses with screws and tension strapping can usually also be mobilized according to the following schedule:
The use of a motorized splint (CPM) is helpful. With axial full weight bearing, it is essential to use forearm supports for gait training in order to relieve the extensor apparatus and reduce retropatellar compression.
After treatment of a patella fracture, forearm supports are required for a certain period of time © S Amelie Walter | AdobeStock
The prognosis for an uncomplicated patella fracture is usually very good and the affected leg can be used again without restriction.
Occasionally, residual symptoms such as swelling or sensitivity to the weather occur and can persist for several months.
As a long-term consequence, premature joint wear can occur in the sliding bearing of the kneecap. This is the case if an irregularity of the cartilage on the back of the kneecap persists after comminuted fractures, despite surgery.
Initial and post-operative local and systemic analgesic therapy must be carried out.
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