Osgood-Schlatter disease (OSD) is a traction apophysitis of the tibial tuberosity: repeated pull from the patellar tendon on the immature apophysis during the adolescent growth spurt.
It is one of the most common causes of anterior knee pain in active adolescents, with a point prevalence of around 10% between 12 and 15 years. It typically presents between 10 and 15 years, earlier in girls than boys, and is bilateral in around 20 to 30%.
OSD is a clinical diagnosis. It often improves as the apophysis fuses at skeletal maturity, but many have lasting symptoms, and symptoms can fluctuate for 1 to 2 years along the way.
The patellar tendon inserts on the tibial tuberosity, which develops from a secondary ossification centre (the apophysis). An apophysis is a traction site rather than a source of longitudinal growth, and while it is partly ossified the cartilage-bone junction is the weak link in the extensor mechanism.
During the growth spurt, bone lengthens faster than the quadriceps and hamstrings, raising traction on the apophysis. Repeated quadriceps contraction in running, jumping and kicking causes microavulsion at the cartilage-bone junction, with reactive ossification, fragmentation and a bony prominence.
When the apophysis fuses (typically 14 to 16 years in girls, 16 to 18 in boys) the weak link goes. The prominence often remains, and a separate ossicle in the distal patellar tendon occasionally causes pain into adulthood.
Risk factors:
The traction apophysitis family shares one mechanism at different sites:
Each is a clinical diagnosis that often improves as the apophysis fuses, although symptoms can last.
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