Front leg problem

[er9m]

Hi, my adult Russian tortoise has a front leg or some kind of problem. He does a sudden moves by his front right leg moving it in and out, like suffering some kind of pain. It lasts for about up to 4 sec. so i do not have video. This problem i have noticed long ago, but it was rare, now it became more often. It seems that there wasn't any injuries with that leg. Does someone had some kind of problems? What this can be and what should i do? I would appreciate any help, thanks.