I have always used knitted as the past tense of knit because that is what I learnt when I was growing up in my family who loved to knit.
I have only recently started knitting again after many years and I was surprised to read the word knit being used as a past tense. When I first read it, with I thought it was just a lack of grammar knowledge by the people using it. But then I saw it being used more and more. So I thought I had better look it up. Perhaps I have been using the wrong word all these years and maybe knitted isn’t actually a word!
I was relieved to see that the Grammarist website states that both knitted and knit can both be used as the past tense of knit.
“The verb knit is traditionally uninflected in the past tense and as a past participle. Knitted is now well accepted, though; it appears about as often as the uninflected form in 21st-century texts from throughout the English-speaking world.
Knitted is safest as a participial adjective (e.g., a knitted scarf), but it also works as a verb (e.g., she knitted all morning). Knit also works in these uses (e.g., a knit scarf, she knit all morning), but it’s falling out of favor.”