The tuberosity of the tibia is a large, knob-like protrusion at the top of the tibia, or shinbone, in each leg. Also known as the tibial tuberosity or the tibial tubercle, this part of the bone is where the patellar ligament is connected to the tibia. This connection of the tibia to the muscle that controls it is what allows the leg to be bent and straightened.
Four bones come together to form a joint at each knee, allowing each leg to bend. The thigh contains a bone called the femur while the lower leg contains two bones known as the tibia and the fibula. More commonly known as the kneecap, the patella protects the front of the knee joint. The tuberosity of the tibia is part of the tibia located just below the patella.
While these bones form a joint, they cannot bend or straighten the leg without muscles. Muscles on the front and back of the knee are what provide the power needed to flex and extend it. Hamstrings are muscles on the backs of the legs that bend the knees while the quadriceps femoris muscles on the front straighten them.
As muscles contract or relax, they transmit force to the bones to which they are attached and cause these bones to move. Tendons are segments of fibrous tissue that connect muscle to bone. One of the quadriceps muscles on the front of each thigh is connected to the tuberosity of the tibia by the patellar tendon. When this particular muscle contracts, it pulls on the patellar tendon, which in turn straightens the knee.
Ailments of the tuberosity of the tibia are more common among children and adolescents than among adults. Fractures may occur before the completion of bone growth due to muscular contraction that is of a force exceeding the strength of the bone. Another growth-related condition, called Osgood-Schlatter disease, is the development of lesions due to excess tension in the patellar tendon.
Avulsion fractures are fractures in which a fragment of bone is completely separated from the rest of the bone. The result of an avulsion fracture of the tuberosity of the tibia is the patellar tendon not being anchored to the tibia. This results in the patient being unable to straighten the leg. Such fractures may occur among children and adolescents during physical activities such as launching or landing a jump.
Younger people are more susceptible to these types of fractures. In the young, the growth plate in the upper tibia has not yet hardened and is, therefore, a structurally weak location. This growth plate hardens and strengthens as a person matures to adulthood. An activity that fractures the tuberosity of the tibia in a child or adolescent often results instead in a patellar tendon injury in an adult. Knee immobilization or surgery is typically prescribed to repair such injuries.
Osgood-Schlatter disease is a condition in which painful swelling and lesions affect the tuberosity of the tibia. This condition is generally due to excess tension on this area of bone growth in the young. These lesions sometimes result from a growth spurt in which the rate of bone growth is faster than that of the tendon. Tension due to abnormal alignment of the legs as well as vigorous sports activity are also sometimes cited as causes of Osgood-Schlatter disease. Treatment of this condition generally involves a combination of rest, anti-inflammatory therapy, and stretching exercises to reduce tension in the affected area.