 They will be given a Patient Information Sheet PIS and be given time during the clinic to ask questions about the study. During this first appointment as per routine current clinical practice they will have an X-ray of their knee and fill in standard questionnaires to score their knee function and pain Norwich Patellofemoral Instability score, Kujala score, PainDetect score, catastrophising score. The patients knees will also be examined by the consultant and a record made of the clinical findings. As per routine practice, a magnetic resonance imaging MRI scan of both knees will be organised for 4 weeks after the original appointment and measurements of knee shape recorded. A total of 32 patients will be invited to join the study to assess the movement of the kneecap in patients with kneecap instability. 