Are you doing any strength training? Especially isometrics, that helps strengthen tendons.
I'm (47m, 2 years of serious running) in the beginning of my fourth marathon block and last two weeks of my 4w 80kpw (which is quite normal for me) gave some atypical symptoms - I have no muscle pain after quality and long runs as such, but severe discomfort which I consider coming from joints, ligaments and tendons. This now almost always the case in WU for first 20 minutes and sometimes I get my legs suddenly collapsed like when a nerve gets hit or clamped.
Another symptom is legs burning at bed time, for an hour but thar happens like once a week, affecting slightly my sleep time.
I started putting two days of recovery (a whole day off and a really easy jogging) between intensive work but that's not helping.
I started watching for food intake making sure I have enough protein and carbs.
I take a bunch of minerals and vitamins as usual.
A month and a half ago I had a 86km ultra, but had a week of rest and smoothly got into the running having no issues.
Please point me what I'm missing here.
Are you doing any strength training? Especially isometrics, that helps strengthen tendons.
Go and see a good physiotherapist. Burning / whole leg pain sounds nervy, but you’re describing things ‘giving way’ which could be meniscal, but you’re saying it’s the tendons and ligaments. No one here can advise you!
Could also be the fascia. Had similar issues but after some sessions on a fascia role the problems were gone
2 years of serious running and 4th marathon block. And a 86k ultra. What you're missing is "this is insane for Homo sapiens."