A 16-year-old boy sustained an acute first-time dislocation to his left patella when he was tackled from behind playing rugby, landing directly on the inside of his knee. The knee was immediately swollen. He went to hospital and was admitted, the patella having spontaneously reduced. He was treated conservatively with a free-moving hinged knee orthosis, discharged, and an MRI scan ordered and referred for advice on his further management.

He now presents 6 weeks later. He has remained on crutches. His knee is not painful and is no longer swollen. He has not regained full muscle power in his leg.

Osgood-Schlatter disease

None

None

Normal rotational profile to the lower limb.

No patellar apprehension. Patella tracked straight. Mediolateral glide ++ bilaterally with a firm end point. No localised tenderness including along the line of the MPFL.

Tibiofemoral joint normal including the ligaments.

Review of his images shows he has open physes. His MRI scan shows a lipohaemarthrosis, a hypoplastic lateral femoral condyle, and a bone bruise pattern consistent with an acute patellar dislocation.