Michael Madsen‘s health was cleared by doctors just days before his sudden death — this according to his longtime friend and assistant, Dougie Smith.

Dougie tells TMZ the ‘Kill Bill’ star was doing a routine hospital visit at UCLA last Friday to get his rotator cuff looked at, citing complications from a fall off a horse about 2 years ago. Michael was apparently considering getting surgery … but due to his upcoming schedule, he decided to put it in a brace for the time being.

Michael had also suffered a minor brain bleed from the fall, so he received a PET scan to ensure everything was looking A-okay … and according to Dougie, Michael got the all-clear from docs.

That’s what, Dougie says, makes Michael’s death so shocking to family and friends, adding … “He looked like he had been in the best health he had been in all year!”

Dougie tells TMZ he was the one who found Michael deceased Thursday morning. He says he had not heard from him all day Wednesday, so he gave his pal a visit … only to find him lifeless in his bed around 8:30 in the morning.

He last spoke to the “Reservoir Dogs” actor Tuesday night, and he describes him as sounding “great.” He noted he was looking forward to Nashville Comic-Con in the coming days.

As we reported … Michael was pronounced dead Thursday morning at his Malibu home. Law enforcement sources tell TMZ Michael’s death is being treated as natural causes.

In addition to being pumped for Comic-Con, Michael was preparing to release a new book called “Tears For My Father: Outlaw Thoughts and Poems” before he died.

He was 67.