I have been battling with a weak knee for several months now. I finally talked to a ortho doc. He suggested that I rest it completely for two weeks, use anti-inflammatories and moist heat. He suggested an exercise I should do. The diagnosis was patellar tendonitis with pateller femoral pain. The pain is a soreness right in the middle of the knee cap. I followed his instructions, swimming a bit but not kicking. Things got a little better, but the soreness remained. The weakness was better, but not perfect. I went riding for the first time on Monday--a lousy 9 miles. Things got worse again. I feel like this will never go away.