The tibia is on the inside of your lower leg. It sits closer to your body’s midline than the fibula, which is the thinner bone on the outside. In anatomy, the inside position is called “medial” and the outside position is called “lateral,” so the tibia is the medial bone of the lower leg. You can confirm this on your own body: the sharp ridge you feel running down the front of your shin is the tibia, and it curves toward the inner side of your leg.
How to Find Your Tibia
The tibia is one of the easiest bones in the body to locate because it sits just beneath the skin along most of its length. While sitting or standing, run your fingers down the front of your lower leg from just below your knee. That sharp, bony ridge you feel is the tibial crest, the front edge of the tibia. There’s almost no muscle covering it, which is why bumping your shin hurts so much.
At the bottom of the tibia, the bone flares out and forms the bony bump on the inner side of your ankle. That bump is called the medial malleolus. The matching bump on the outer side of your ankle is the bottom of the fibula, called the lateral malleolus. So if you grab both ankle bumps with your fingers, your thumb on the inside is touching the tibia and your fingers on the outside are touching the fibula.
Tibia vs. Fibula: Size and Function
The two bones of the lower leg look nothing alike. The tibia is the larger, thicker bone and carries nearly all of your body weight. In a neutral standing position, the fibula handles only about 6.4% of the load passing through the lower leg. That percentage shifts depending on foot position: pointing your toes down decreases the fibula’s share, while flexing your foot upward increases it, reaching as high as 19% during high-force activities like running.
Because the tibia bears so much more weight, its internal structure is built for compression throughout its length, with thick, dense cortical bone along the entire shaft. The fibula, by contrast, has a more varied structure along its length, adapted more for bending and rotational forces than for supporting your weight directly. This difference explains why the tibia is roughly two to three times wider than the fibula and why tibia fractures are a much bigger deal for mobility than fibula fractures.
Where the Tibia Connects
At its top end, the tibia forms the lower half of the knee joint. The broad, flat surface at the top of the tibia (the tibial plateau) is where the rounded ends of the thighbone sit, separated by cartilage and the meniscus pads that cushion the joint. Your kneecap rides in a groove at the front of this junction.
At its bottom end, the tibia forms the inner portion of the ankle joint. It meets the talus, the small bone that sits on top of the heel bone, creating the hinge that lets your foot flex up and down. The fibula joins in on the outer side, and together the tibia and fibula create a socket that grips the talus like a wrench. Ligaments on the inner ankle connect to the tibia’s medial malleolus, while ligaments on the outer ankle attach to the fibula’s lateral malleolus.
Why Shin Pain Happens on the Inner Side
If you’ve ever had shin splints, you probably noticed the pain runs along the inner edge of the tibia rather than the outer side. This isn’t a coincidence. The condition, formally called medial tibial stress syndrome, involves repeated stress on the muscles and connective tissue that attach along the tibia’s inner border. Several calf muscles anchor to the back and inner surface of the tibia through tough fibers that connect directly to the bone’s outer membrane. When those muscles pull repeatedly during activities like running or jumping, the membrane becomes inflamed and the bone itself develops tiny areas of damage.
The pain typically shows up along the lower two-thirds of the inner tibial border and feels like a diffuse tenderness or ache that starts during exercise and eases with rest. It’s different from a stress fracture, which tends to produce a sharp, pinpoint pain in one spot. Shin splints spread across a broader area, often more than five centimeters of the inner shin, and you can usually reproduce the soreness by pressing along that inner edge with your fingers.
When the Tibia Breaks
Tibial shaft fractures are among the most common long bone fractures, partly because the tibia has so little soft tissue protecting it along the front and inner surfaces. The most common surgical repair involves placing a metal rod inside the hollow center of the bone. This approach shares the mechanical load with the healing bone rather than replacing it entirely, which allows most people to start putting some weight on the leg relatively early in recovery. Full healing of a tibial shaft fracture typically takes several months, with the timeline depending on the fracture’s severity and location.
Because the tibia handles the vast majority of lower-leg weight bearing, a tibial fracture affects your ability to walk far more than a fibula fracture would. A broken fibula on its own often allows limited weight bearing with a boot, while a broken tibia almost always requires more aggressive treatment and a longer period before you’re back to normal activity.