As believable it would be that he has a catheter bag, that is a hip brace by the looks of it. I had to wear one when I was younger when my left leg decided to forcefully remove itself from my hip in a ski accident. My Grandfather wore one when he had a hip replacement. What yaniv is sporting looks like a hip abduction brace, from my experience having to hobble around in one for almost a year, his stride and posture indicates he is a lying sack of shit.
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It definitely isn't his, the fitting for it is for someone much smaller, the waist support looks to be over stretched and it is sitting too hight. It is more than likely a craigslist purchase or it belonged to his mom, those things are not cheap either some cost upwards of 800 bucks.