The tibia, or shin bone, spans the lower
leg, articulating proximally with the femur and patella at the knee joint, and
distally with the tarsal bones, to form the ankle joint. It is the major weight-bearing bone of the lower leg.
Proximally, there are five key features of
It widens and forms two condyles—the lateral and medial—that
articulate with the condyles of the femur.
Between the two condyles is the
intercondylar fossa, a small grove, into which two intercondylar tubercles sit.
Numerous internal ligaments of the knee joint attach to these tubercles and strengthen
On the anterior surface of the proximal region and inferiorly
to the condyles is the tibial tuberosity to which the patella ligament
The shaft of the tibia is triangular and
the soleus muscle, which gives the calf its characteristic shape, originates on
the posterior surface.
Distally, the tibia also widens to aid with
weight bearing and it displays two key features. The medial malleolus is a bony
projection that articulates with the tarsal bones to form the ankle joint.
Laterally, there is the fibular notch that articulates with the fibula.
The fibula also spans the lower leg, although
proximally it does not articulate with the femur or patella. It serves more as an
attachment point for muscles rather than a weight-bearing bone.
Proximally, the fibula head articulates with
the lateral condyle of the tibia, and the biceps femoris attaches to the fibula
head. As with the tibia, the shaft of the fibula is triangular and numerus
muscles are involved in the extension and flexion of the foot. These muscles originate from the fibula's
surface and include the extensor digitorum longus, soleus, and flexor hallucis
longus, among others.
Distally, the fibula forms the lateral malleolus, which is
more prominent than the medial malleolus of the tibia. It also articulates with
the tarsal bones to form the ankle joint.