This 17 year old elite footballer presents with recurrent locking symptoms in his left knee. He has had mild intermittent discomfort in his knee for some time, but over the last month or so has developed recurrent locking. His presentation was provoked by an episode where his knee “jammed out straight” while he was playing a game. It remained locked for 10 minutes. The episodes of locking prior to this had been more brief, with the knee unlocking very quickly. The knee had swelled up markedly since the most recent episode.
He had non-specific clinical examination findings including an antalgic gait, a moderate effusion and generalised tenderness.
A large and irregular looking osseous body is seen in the suprapatellar recess on the lateral x-ray image. An MRI further demonstrates a 20 mm osteo-cartilagenous loose body in the supra patella pouch. There is chondral irregularity in the lateral aspect of the trochlea with fibrocartilage infill. There is some underlying bony oedema but the cartilage coverage is reasonable. The donor site shows evidence of healing and the loose body is far larger than this region. The menisci and remaining cartilage in the surfaces of the knee are normal.
Given that the player was experiencing recurring pain and locking he underwent an arthroscopy. A large loose body was removed via an extended medial portal. The donor site (20mm x 15mm) was clearly visible at the lateral border of the trochlea. It was however largely non-articular and had fibrocartilage infill (which was stable to probing). The remaining cartilage was normal. Following surgery the player started a physiotherapy-based programme with a focus on early movement. He was able to return to football within three months of his surgery.
Juvenile OCD is seen more frequently in active, athletic children and adolescents (than in those who are more sedentary). A history of a traumatic episode is present in 40-60% of cases. Patients typically present with longstanding pain that is aggravated by physical activity. There may be a restricted range of movement, limping and swelling of the superficially located joints. Mechanical symptoms like locking, catching or grinding are late-stage features, and suggest a loose or detached fragments. The lesion can sometimes be seen on x-rays however these can lack sensitivity in the early stages. An MRI is a more sensitive test but can sometimes underestimate the grade of injury. In most cases a diagnostic arthroscopy is suggested to further evaluate the injury and where possible stabilise it.
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