An 11-year-old female player presented with a one year history of unilateral, well-localised, anterior knee pain. She was not able to identify a clear traumatic precipitant. There was a clear relationship to physical activity with the pain becoming worse playing football (and other sport) and improving with rest. The only finding of note on clinical examination was localised tenderness about the inferior pole of the patella.
A lateral x-ray image shows an ossicle lying adjacent to the inferior pole of the patella. This is further demonstrated on MRI sequences. The ossicle has a sclerotic margin dividing it from the remainder of the patella, and measures 14×4.5×9 mm. There is increased signal intensity on all sequences suggestive of bone marrow oedema/reactive signal intensity change with a small amount of adjacent bone oedema in the inferior pole of native patella. There is no fragment separation, fluid signal intensity fracture cleft or discernible synchondrosis. There is also no major thickening of the proximal patellar tendon with no tendon tear or major abnormality. The knee is otherwise normal. The radiological appearances are consistent with an incompletely incorporated secondary ossification centre or traction apophysitis.
The player was treated with activity restriction with a presumed working diagnosis of Sinding Larsen Johansson Syndrome. The player avoided running-based sport for one month. During this period her symptoms improved substantially. She was then able to return to football with a 50% reduction in her pre-injury training volume. She was then able to progressively increase her training load over the next few months. Six months after her initial presentation her symptoms had completely resolved and she had returned to normal football.
Two clinicians, Sinding-Larsen and Johansson, independently described a syndrome that occurred in adolescent patients consisting of tenderness at the inferior pole of the patella associated with radiographic evidence of fragmentation of the pole. This is now known as Sinding-Larsen-Johansson disease (SLJD). Like Osgood-Schlatters disease, where the tibial tubercle is involved, this condition is a traction apophysitis and is mostly caused by repeated microtrauma due to traction on the distal pole of the patella from quadriceps muscle contractions. The syndrome typically affects children and adolescents between the ages of ten and fifteen years old and in almost all cases is self-limiting.
It is important to be aware that there are other conditions that can cause similar x-ray appearances, and that these may require different treatment. A patellar sleeve fracture is one of these conditions. In contrast to SLHD, sleeve fractures are associated with acute trauma, most frequently an explosive movement involving rapid contraction of the quadriceps. While the x-ray appearance may appear similar, MRI findings are often substantially different. Sleeve fractures often involve avulsion of the periosteum, retinaculum and the patella articular cartilage. These generally require surgical treatment.
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