Stifle Problem

May 31st I took Muddy out to ride. It was the first time in a month that he was ridden. At the walk, he felt fine. I instantly knew that something was wrong at the trot. He was a bit off. I hoped off and lunged him so I could see what was going on. He bobbled just a tad on his left back leg. There was no obvious injury. Who knows how long he's been off since all I've been doing is going down to his pasture to groom and feed him. Crap! Dr Simpkins came out June 4th. He was to do the usually spring stuff and I had him take a look at Muddy's leg. We trotted him in the round pen. He was so lame! Much worse than Sunday. Dr Simpkins examined him and determined that it is his stifle. Now before we came back to Green Star, Muddy's left stifle was starting to click with every stride. However, it stopped after he was turned out 24/7. We don't know if it's an injury or if it's the onset of arthritis. I hope it's just a mild injury. I'm not sure I can handle stifle arthritis again. It's really bad. So for the rest of this week and next, Muddy will be kept in a stall/paddock combo. He's to have bute for a few days. Next Friday I will try to trot him again. If he's still off, then he's going in for xrays.