Fracture can be caused by direct or indirect forces.
- Direct impact to patella can occur from a fall on a flexed knee landing directly on patella or motor vehicle crash. This can result in a transverse fracture pattern (more common in younger adults) or a comminuted fracture (more common in elderly patients and those with osteoporotic bone).
- Indirect impact can occur with sudden flexion of the knee against a contracted quadriceps muscle (depending on the force and properties of the muscle / bone / tendon, something in the patient's extensor mechanism will break, whether it is the quadriceps tendon, the patellar tendon, or the patella itself). Avulsion fractures involve the superior / inferior pole.
S82.009A – Unspecified fracture of unspecified patella, initial encounter for closed fracture
51037009 – Fracture of patella
- Bipartite or tripartite patella (these are normal anatomic variants; 20% of the time, the patella will develop from 2 or 3 ossification centers instead of 1)
- Patellar dislocation (medial patellofemoral ligament disruption)
- Patellar subluxation
- Quadriceps tendon rupture
- Patellar tendon rupture
- Quadriceps tendonitis
- Patellar tendonitis
- Tibial plateau fracture
- Distal femur fracture