A 13-year-old boy presents to the clinic with gradual onset of lef anterior knee pain, particularly associated with sport, worsening over the previous 6 months. He is otherwise ft and well and plays football. It does not really limit what he does, but it does ache aferwards. On examination the only abnormal fnding was a lateral-tomedial movement of the patella at 20° of flexion .It was felt that some VMO strengthening exercises would improve his symptoms. He was referred to physiotherapy .? Question 1 What is the most likely diagnosis ?? Question 2 What is its natural history ?? Question 3 What in the history and examination would suggest further investigations should be requested? ? Question 4 What diagnoses should be considered and what further investigations specifc for each ?At the age of 15 years old, he was admitted via the Emergency Department following a twisting injury to his lef knee playing soccer. He had immediate swelling and was unable to weight-bear on the leg. ? Question 5 What is the most likely diagnosis? Examination on the ward found that his knee was swollen. He could flex the knee comfortably to 450 but was unable to extend actively because of discomfort. Palpating the extensor mechanism showed that it was intact. He had “some” tenderness on the anterior part of the medial tibiofemoral joint line. He was tender over the medial retinacular ligament. Te ACL was noted to be normal.