Horses' back legs clicking ?

This could be a lot of different problems . But before we go trying to diagnosis and getting upset at many answers here are a few things to address . It could be the onset of arthritis in hocks ,fetlocks and or legs hips .BUT THIS ALSO IS THE WAY HORSES/ANIMALS REVEAL THEIR HISTORY OF PAST PROBLEMS AND THE ADJUSTMENT TO NEW LIFE ,HANDLING AND SURROUNDINGS etc;..I SUGGEST YOU GO TO LOCAL DRUG MART AND GET SOME MSM PILLS AT 1000 MG'S TO 1500 MG'S AND GIVE YOUR HORSE CRUSHED IN FEED 4 PER DAY FOR ABOUT 30 DAYS THEN GO TO 2 PER DAY EVENTUALLY BY 2 MONTHS TO 1 per DAY. This is great for pain as it has anti inflammatory indications an cartilage re- builder helps greatly. The thing about MSM is all natural and is proven on humans and animals i brought this to Canada in 1970's and it works well. When horse's shift their weight change leads etc. they are compensating for a leg or back problem. Wait till your trainer takes a look before jumping to conclusion's he may suggest a Vet. exam.