The tibia and femur bones form the main articulation of the knee joint, and the tibia also articulates with the fibula bone at the outer side of the knee.
Between the tibia and femur is the meniscus, which accommodates the rounded ends of the femur and the flattened top of the tibia. The two cruciate ligaments reach between the two bones right in the centre of the knee.
The flattened top of the tibia is known as the tibial plateau.
In this X-ray of the tibial plateau you can see the central tibial spines where the cruciate ligaments (which do not show on X-ray) attach. Equally the two menisci cannot be seen on an X-ray, appearing only as a 'gap' between tibia and femur.
Illustration looking down on the tibial plateau from above. This shows the key structures of the tibial plateau - the two menisci and the two cruciate ligaments (cut for illustration purposes), plus the popliteus tendon passing along the lateral meniscus on the one side.
Looking at the upper tibia from the lateral side you can see the tibial tuberosity where the patellar tendon attaches. On the side you can also see the anterolateral ligament (ALL) attaching tibia to femur.