Okay lar... the answer is fibula... go look at the anatomy, it
is shaped like a triangle if you do a cross section over it. There
is hardly any muscle attachment in this bone compared to the tibia,
nor does it participate in the knee joint. It does participate in
the ankle joint and form the lateral malleolus, the bulge you see
on the outer part of your ankle joint, the inner part's bulge is
formed by the tibia.
The fibula and tibia are quite superficial, and any accident
involved would cause an open wound almost inevitably leading to a
compound fracture of both bones. It takes a great amount of time to
heal, maybe 6 months to a year, depending on the severity.
