At the top of the tibia, the bone is relatively flat and this region is referred to as the tibial 'plateau'. The tibial plateau is an important area because it is where the two menisci are seated and the two cruciate ligaments are tethered.
Fractures or bone breaks of the tibial plateau not only have the potential to upset the delicate mechanics of the knee, but they are also frequently missed by the emergency team despite the patient complaining of severe pain in the knee following an injury.
The issue is that one needs X-rays in two different planes to be able to see the often subtle outline of the fractured area. Also, the bone may not necessarily break off, but may be crushed and the fragment depressed, and it needs an experienced eye to appreciate this on X-ray.