A 19-year-old man presented with problems with his right knee that began at the age of 15 years. At that time he was playing soccer when he was struck on the lateral side of the knee. He fell to the ground and at point of contact felt a “pop” in his knee. The knee swelled slowly over the course of approximately 2 h. He went to the Emergency Department and then returned the following day, but no diagnosis was made. Since then he had had approximately five episodes where his knee gave way and he felt the kneecap move out of joint and return spontaneously. All these episodes occurred either during sports or after jumping when dancing. His knee would then take about 4 weeks to return to normal, until the last episode since when he had great difficulty trusting his knee, particularly on the stairs. He wanted to get back to soccer or running.