Tennis Player...old, 66..decent Shape, Doc Says I'm Loaded With Arthritis...esp.lft

tennis player...old, 66..decent shape, doc says I'm loaded with arthritis...esp.lft knee and hip...try to build muscle around effected areas for support...prior to season, feel pretty strong...we get to playin' (mostly 20-30 somethins') I start flying around (relatively speaking :) ...things start going south after 3-4 matches...light swelling, twinges on inside- front of left knee...I ice afterwards, comfortable when not in playing mode, unsure how to approach from here...any sort of knee bearing exercise on next day is met with this twinge...want to exercise but seems to worsen...3 wines, half a j, 2 advil...I feel swell :)