Case study: An unusual football knee injury

A 13-year-old boy suddenly seemed to be losing his form on the pitch, explains Dr Keith Barnard.

I had discussed the various merits of the Premiership contenders with Mr Richards on more than one occasion. So when he brought his son Samuel along because he was struggling with his game, I was perhaps more than usually interested.

Strange symptoms
Samuel explained how the pain came on when he was running and became worse as the game went on.

Samuel showed me his right knee and pointed below the kneecap. I began to embark on my explanation of Osgood-Schlatter disease, but as I examined him, I paused when I could not find the typical small tender swelling over the anterior tibial tubercle.

However, when I pressed just below the patella on the patellar tendon, he jumped and gave a loud 'Ow'.

I was puzzled. Everything else was normal, there was good strength in his quads, no crepitus in the joint or from the patella tendon, no effusion in the knee joint and a full range of movement. I even tested the stability of the lateral and cruciate ligaments and checked for meniscal injury, but they were all fine. Still half-believing this was Osgood-Schlatter, I sent him for an X-ray to make sure.

Calcification of the knee
The report was something of a surprise. The radiologist said that lateral views showed some areas of calcification below the inferior pole of the patella in the region of the patellar tendon.

There was a little soft tissue swelling as well. These findings indicated Sinding-Larsen-Johansson disease. I had to haul the books out to enhance my faded knowledge.

Sinding-Larsen-Johansson disease occurs in children and adolescents aged 10-14 years and presents with tenderness and soft tissue swelling over the inferior pole of the patella. X-rays show osseous fragmentation. It is not an apophysitis or osteochondritis, but usually traumatic.

I took comfort in the fact that the pathogenesis is similar to that of Osgood-Schlatter disease. It is traction phenomenon that causes a tendinitis of the proximal attachment of the patellar tendon. The tendinitis is followed by calcification or ossification, that is eventually usually incorporated into the lower pole of the patella.

I was able to reassure them the condition we were dealing with would get better and that it was pretty unusual, which impressed the budding footballer.

Treatment
The natural course of the condition is spontaneous resolution over three to 12 months, with no specific treatment, although quads exercises can help.

The question of Samuel's fitness for the big game came up. I took the line that if he played and the pain prevented him from playing 100 per cent, he might worry he had made the wrong decision, which he seemed to accept.

By the start of the next season he was back to normal.

Dr Barnard is a former GP in Fareham, Hampshire.

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