While the diagnosis of Osgood-Schlatter disease (OSD) is usually pretty straight forward and purely a clinical diagnosis, due diligence must be considered to verify a more severe diagnosis is being missed.
Lazerte and Rapp, in examining resected operative specimens in patients with Osgood-Schlatter disease, demonstrated avulsion fractures in the distal portion of the tibial tubercle. 
Not all patients with Osgood-Schlatter disease (OSD) need radiography, since the diagnosis is clinical. However, plain films are should be obtained at least once in the evaluation and treatment to rule out other etiologies, such as neoplasm, acute tibial apophyseal fracture, and infection.
Radiographs may indicate:
Superficial ossicle in the patellar tendon
Irregular ossification of the proximal tibial tuberosity
Calcification within the patellar tendon
Thickening of the patellar tendon
Soft-tissue edema proximal to the tibial tuberosity
The Osgood-Schlatter lesion is best seen on the lateral view, with the knee in slight internal rotation of 10-20°.
The most common finding is that the knee films are normal, especially if the child is in the preossification phase.
The acute phase of OSD may reveal a prominent and elevated tibial tubercle with anterior soft-tissue swelling.
In severe cases, radiographs may reveal radiodense fragments or ossicles separated from the tibial tuberosity. (An ossicle is seen in the image below.)
Occasionally, the radiographs may reveal irregularity, fragmentation (seen below), or increased density of the ossification of the tibial tubercle. This pattern may be a normal variant in asymptomatic children.
Other Imaging Modalities
Advanced Imaging is not necessary to make the diagnosis of Osgood-Schlatter disease (OSD) but may be necessary to verify that another diagnosis is not present.
Nuclear Medicine Bone Scan if obtained may demonstrate increased uptake in the area of the tibial tuberosity.
Computed tomography (CT) scanning or magnetic resonance imaging (MRI) may reveal changes at the insertion of the patellar tendon.
MRI may assist in diagnosis of an atypical presentation. It may eventually play a role in staging of the disease and prognosticating the clinical course. However, MRI’s role in diagnosis, prognostication, and management is currently limited.  Magnetic resonance imaging if obtained to rule out other diagnoses may show increased bony edema of the tibial tuberosity.
Laboratory evaluation is not indicated for Osgood-Schlatter disease (OSD) unless other diagnoses are being entertained.
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