Osgood–Schlatter disease (OSD) is inflammation of the patellar ligament at the tibial tuberosity (apophysitis)[3] usually affecting adolescents during growth spurts.

[6] After growth slows, typically age 16 in boys and 14 in girls, the pain will no longer occur despite a bump potentially remaining.

[11] Intense knee pain is usually the presenting symptom that occurs during activities such as running, jumping, lifting things, squatting, and especially ascending or descending stairs and during kneeling.

It has unique features such as detection of an increase of swelling within the tibia or the cartilage surrounding the area and can also see if there is any new bone starting to build up around the tibial tuberosity.

[citation needed] OSD may result in an avulsion fracture, with the tibial tuberosity separating from the tibia (usually remaining connected to a tendon or ligament).

[citation needed] Type II: The articular surface of the tibia remains intact and the fracture occurs at the junction where the secondary center of ossification and the proximal tibial epiphysis come together (may or may not require surgery).

[citation needed] Type III: Complete fracture (through articular surface) including high chance of meniscal damage.

[18] Direct stretching of the quadriceps can be painful so the use of foam rolling for self myofascial release can help gently restore flexibility and range of movement[19][20] Treatment is generally conservative with rest, ice, and specific exercises being recommended.

[21][24] Bracing or use of an orthopedic cast to enforce joint immobilization is rarely required and does not necessarily encourage a quicker resolution.

[citation needed] The condition is usually self-limiting and is caused by stress on the patellar tendon that attaches the quadriceps muscle at the front of the thigh to the tibial tuberosity.

Following an adolescent growth spurt, repeated stress from contraction of the quadriceps is transmitted through the patellar tendon to the immature tibial tuberosity.

This can cause multiple subacute avulsion fractures along with inflammation of the tendon, leading to excess bone growth in the tuberosity and producing a visible lump which can be very painful, especially when hit.

Several authors have tried to identify the actual underlying etiology and risk factors that predispose Osgood–Schlatter disease and postulated various theories.

However, currently, it is widely accepted that Osgood–Schlatter disease is a traction apophysitis of the proximal tibial tubercle at the insertion of the patellar tendon caused by repetitive micro-trauma.

In a retrospective study of adolescents, old athletes actively participating in sports showed a frequency of 21% reporting the syndrome compared with only 4.5% of age-matched nonathletic controls.

[34] The symptoms usually resolve with treatment but may recur for 12–24 months before complete resolution at skeletal maturity, when the tibial epiphysis fuses.

237 of these people responded well to sport restriction and non-steroid anti-inflammatory agents, which resulted in recovery to normal athletic activity.

[39][40] It was found that the leading cause for the incidence of the disease was regular sport practicing and shortening of the rectus femoris muscle in adolescents that were in the pubertal phase.

[42] This risk ratio shows the anatomical relationship between the tibial tuberosity and the quadriceps muscle group, which connect through the patella and its ligamentous structures.

[43] The high risk ratio with people with the disease and palpatory pain is likely the reason that the number one diagnosis method is with physical examination, rather than imaging as most bone pathologies are diagnosed.

[44] It's possible that the rapid tuberosity bone development and other changes to the proximal aspect of the knee with those who have the disease is the culprit to the increased risk.