Tibia

From ArticleWorld

The tibia is the primary supportive bone in the lower leg of humans. It runs along the length of the lower leg along with the fibula. The anterior surface of the tibia can be felt in the front of the lower leg and is sometimes called the “shin bone”.

Anatomy

The proximal aspect of the tibia is composed of two condyles that form the articular surface of the knee along with the distal femur. The two condyles are called the medial and lateral condyles. They are covered in smooth lubricated cartilage that keeps bone from contacting the tibia bone. The upper anterior part of the tibia has a prominence called the tibial tubercle.

The ligaments that support the knee attach to various aspects of the tibia. The patellar ligament attaches to the tibial tubercle. The medial collateral ligament attaches to the lateral (or tibial) collateral ligament. The posterior aspect of the proximal tibia has a small depressed area that attaches the posterior cruciate ligament. The lateral aspect of the tibia also forms the attachment for the proximal end of the fibula. The iliotibial band of the thigh has its lower attachment at the lateral tibia.

The shaft of the tibia is actually triangular in shape. It has an anterior surface that contains the tibial tubercle and attaches the deep fascia of the leg. The medial border is the aspect that faces the medial border of the opposite tibia. The lateral border is also called the interosseous crest because it attaches the long interosseous membrane that stretches between the tibia and fibula.

The lower tibia forms the articular surface of the ankle. It is covered in smooth cartilage. There is an inferior prominence on its medial (inner) aspect that is called the medial malleolus. The medial malleolus forms the bump one can feel on the inner aspect of the ankle.

Function

The tibia helps to extend the knee by virtue of its attachment to the distal ends of the knee extensors. It also helps to flex the knee by attaching the knee flexors at their most distal ends. The muscles surrounding the tibia help to flex the ankle. The gastrocnemius muscle forms the bulk of the posterior musculature of the lower leg and is attached proximally to the tibia. This is the muscle that flexes (or plantar flexes) the ankle.

The soleus muscle is partially attached to the proximal tibia as well and helps give some rotation to the ankle. Interestingly, most of the ankle extensor muscles are attached to the fibula and not to the tibia.

Conditions

The tibia and/or the fibula can become fractured in an injury. The tibial fracture is more severe as it is the supportive bone to the rest of the leg and body. In some situations a young teen can develop an inflammation of the tibial tubercle that, with rest for a prolonged period of time, will resolve spontaneously. This condition is known as Osgood-Schlatter’s Disease.