The thigh bone, which is also called the femur, is the bone inside the human body located between the hip and the knee of each leg. The top of the thigh bone is connected to the hip, forming the hip joint, and the bottom of the bone is connected to the knee, forming the knee joint. This bone is the longest one in the human body. The total length of the thigh bone usually varies from person to person and is dependent on height, but it is around 19 inches (48 cm) long in the average person. This bone can hold up to 30 times the weight of the average adult and makes it possible for humans to be able to walk, jump, and run.
There are many different parts that make up the thigh bone. The trochanters are two of the most identifying features of this bone. These are usually referred to as the greater trochanter and the lesser trochanter because one is smaller than the other. The function of the trochanters is to hold the muscles of the hip and thigh area in place. Trochanters are typically very noticeable because they are bony and irregularly shaped, and a person may even be able to feel them on the outside of the legs.
Some other parts that make up the thigh bone are the condyles. There are also two of these, which are referred to as the lateral and medial condyles. The function of the condyles is to fit into the small spaces of the tibia, which is located at the knee joint. A person can easily bend and straighten her knees in part because of these condyles. The condyles may also help with knee rotation.
The thigh bone is considered the strongest bone in the human body and also one of the most important. In spite of its size and strength, it does tend to weaken as a person ages. Women who have osteoporosis are particularly at risk for problems with their thigh bones. Surgery is often necessary to correct fractures that occur in the thigh bone, but this normally depends greatly on the severity of the injury. Apart from osteoporosis, car accidents are another major cause of fractures and breaks in the thigh bone because it generally takes a great amount of force, such as what may occur in the average car accident, to break such a strong bone.