One week ago I slipped and fell. I hit my head hard and my ribs and scapula are hurt too.

The scale jumped up 6 pounds 2 days after. The scale has been down 4 pounds and back up 2 pounds. I'm eating the same. Is this weight gain from swelling?

Swelling and possibly the sodium in any of your painkillers or medicines. Medicine can have so many hidden side effects these days. Please do not stop taking the meds if you are on anything. Once you have healed and off the medication, your weight will start coming back down. Praying a speedy recovery!!

If you want to know if what you are gaining is fat, remember that if you consume 3,500 calories more than you burn, then you can gain a pound, burn 3,500 more than you consume, you lose a pound. Generalizing an immobile person's resting metabolic rate at 2,000 calories, what you have to ask yourself is did you consume more calories than you burned? In 2 days, did you consume 6 x 3,500 = 21,000 + 4,000 (BMR) = 25,000 calories in two days?

4 months post op, I highly doubt it. I am close to 3 years post op and I cannot consume that much. So, this tells us your gain is attributed to something else. My vote is swelling and Water retention.

Yeah, I'm with the others on this. Swelling and water retention. No way that could be fat. Best wishes for a speedy recovery.