Osgood Schlatter's Disease is a tibial tuberosity apophysitis, which is the medical name for inflamed bone at the site of the tibial tuberosity growth plate, in children.  

Osgood Schlatter's disease is an inflammation of the bone at the top of the tibia (shin bone), where the tendon from the patella (kneecap) attaches. It is an overuse knee injury rather than a traumatic injury. While Osgood Schlatter's disease is a relatively uncommon, it is a quite debilitating knee injury that occurs in young active children/adolescents. 

What the Symptoms of Osgood-Schlatter's Disease?

Osgood Schlatter's disease presents in growing boys and girls as: Local pain, swelling, and tenderness over the tibial tuberosity at the attachment of the patellar tendon. Pain is experienced during exercise (e.g., running, jumping) or with a direct contact, such as in kneeling. Stairs, squatting and kneeling may be painful. Quadriceps weakness can be present is chronic cases. Bilateral symptoms occur in 20-30% of cases. The apophysis may be enlarged in later stages, which looks like a lump that is tender in its active phase.

What Causes Osgood-Schlatter's Disease?

Strong repetitive quadriceps contractions are thought to cause a traction force on the tibial tuberosity, disrupting the immature bone. There is a higher incidence in active children during the adolescent growth spurt.

As a child grows, bones go through different stages of development: 

The tibial tuberosity is initially cartilaginous (cartilaginous stage). 

It then enters the apophyseal stage when the secondary ossification centre (apophysis) appears.

The unity of the proximal tibial epiphysis with the tibial apophysis marks the epiphyseal stage.

Lastly, when the growth plates fuse, the bony stage has been reached.

Children are most susceptible to Osgood-Schlatter's disease when their bones are in the (2nd) apophyseal stage. During this phase, the apophysis is unable to withstand high tensile forces. When presented with strong, repetitive muscle contractions, micro-fractures occur in the immature area. The separation results in symptoms typical of Osgood Schlatter's disease, as well as the irregular bone growth that explains an enlarged tibial tuberosity afterwards. 

Another potential cause of Osgood Schlatter's disease has been the lack of growth of the quadriceps in comparison to the femur. During a growth spurt in a child, the lengthening of the muscle is unable to keep up with the lengthening of the rapidly lengthening femur, resulting in an increased tensile force on the tibial tuberosity.

Who Suffers Osgood Schlatter's Disease?

Osgood Schlatter's disease usually strikes adolescents who are active during their growth spurts, which is the two year period where they grow most rapidly. Osgood-Schlatter's Disease is most common in boys but can affect either gender if the children are active. Tight thigh muscles also predispose you to Osgood Schlatter's disease. The most prevalent groups are Boys: ages 11-15 years – Girls: ages 8-13 years. Activities involving repetitive, strong quadriceps contractions, such as in jumping, running, volleyball, basketball, soccer, gymnastics, dance, netball and ice skating are most at risk.