About a month ago I knelt down and felt a sharp pain in my knee as if I had nelt down on a bolt as I have done in the past - I'm an untidy worker ! My knee went and after I got off the floor I looked for the " bolt " and found nothing . Nursing my now painful knee I thought little of it . About a week later and after my knee had , I thought , recovered from the bolt caused bruising I gingerly knelt on the tiled floor of Morrison's supermarket to get some Pepsi-Max from the back of the bottom shelf . A loud animal scream was heard all along the Isle and I was seen rolling around the floor in agony ( how embarrassing ! ) I had found another " invisible bolt " Another ten days and the tenderness in my knee had departed so I decided to examine it carefully . I found there was something small and hard under the skin which moved around quite a bit when i pressed on it . The " invisible bolt " was inside my knee ! An appointment was made with Dr Moore on