What’s Biden hiding on his right knee?

This footage is from the same day that Joe Biden fell after delivering a commencement speech in Colorado when I rewatch the clip as well as one other clip from the same day, I noticed some thing visible some type of device that is Neil level under his pants on the right side. Let me know what you think it is and if this device could be responsible for him falling down 

#BidenFail #BidenFalls #republicans #MAGA #Trump2024