Moving this to the Michel thread...
I know I will take a lot of grief for this... but here's what I know and what I speculate: Sony Michel ruptured his ACL in his left knee in 2011. ACL tears are linked to a significant increase in OA later in life, and that chance is increased at least 6x if there is any damage at all to the surrounding cartilage and/or meniscus. I have no idea if his ACL rupture involved these structures, but considering his "bone on bone" condition in his knee, I have to assume yes.
In 2017 he had a grade 1 ligamentous strain. Not a huge deal by itself, but factor in that knee is already slightly less stable after the acl reconstruction (the surgeon can never get it 100% back to normal; it's about the stability after a grade 1 tear), it increases the chances for further micro damage to the cartilage and further progression toward OA.
2018 he had a mysterious left knee injury that resulted in draining of the knee and then further surgery to likely clean up the meniscus and other loose cartilage. Again, another surgery that creates trauma at the cartilage level, progressing OA.
He is reported to have a "bone on bone" issue in his left knee, which is not surprising given his significant injury history to this area. IMO his knee may be in worse shape than Gurley, but who knows- ita pure speculation, however I say that because to my knowledge Gurley doesnt have the injury history Michel has. We saw how quickly Ajayi's knee went in the dump, and I could probably dig into his thread and find at least a few posts where I said his knee issues raised red flags for me. I took grief in that thread too.I liked him early in his career and soured once I realized his knee was limiting him.
Michels knee is only going to progress. That's a certainty. I suspect they drafted Harris to take some volume off Michel, probably to help prolong his knee. Similarly to what Miami and Philly tried with Ajayi and what LAR is likely doing with Gurley. I'm not saying Michels knee gives out on him this year, but I do think he is at or approaching a sell high status and may not have a long career in the NFL.
ETA: Gurley did tear his left acl in 2014