This miracle claim has been refuted decades ago yet every few years it pops up a new generation of clueless Muslim preachers, who repeat the same false claim again and again.
Sahih Muslim, Book 5, Hadith 2199
'A'isha reported Allah's Messenger (ﷺ) as saying: Every one of the children of Adam has been created with three hundred and sixty joints; ...
Was Muhammed the first and only to know this information? Certainly not, as the Chinese knew it much before Muhammad.
Luxuriant Gems Of Spring And Autumn Annals, Dong Zhongshu, P. 10:
Other creatures suffer troubles and defects and cannot match Heaven and Earth; man alone can match them. Man has 360 joints, ...
perceptive, his hearing will be sharp, his taste will be sensitive, his oral expressiveness will be perfect, and all his three hundred and sixty joints will work well.
Human beings have 360 joints, nine body openings, and five yin and six yang systems of function.
According to Nathan Sivin, this was already common teaching in the third century B.C., i.e. it is apparently documented even earlier. We find that this correspondence is also part of (at least some forms of) Buddhism (Buddha lived roughly 500 B.C.).
Nathan Sivin, State, Cosmos, and Body in the Last Three Centuries B.C. [For Harvard Journal of Asiatic Studies]
... Nichiren Daishonin’s Buddhism teaches that our existence is identical to the universe as a whole, and the universe as a whole is identical to our existence. Each individual human life is a microcosm. ... There are some 360 joints in the human and they stand for the days of the year. The twelve major joints signify the twelve months.
Gangyo Is A Grand And Noble Rite
Thus, Muhammed wasn't the first or only person to know this.
There's proof that Muhammad knew other cultures:
"I went to Allah's Messenger (ﷺ) along with some persons and he was saying: I intended to prohibit cohabitation with the suckling women, but I considered the Greeks and Persians and saw that they suckle their children and this thing (cohabitation) does not do any harm to them (to the suckling women). "
Moreover, there is no evidence that the human body has 360 joints. It is just a random number that doctors like to regurgitate since it was arbitrarily decided over 2000 years ago by Chinese doctors that this number is cool.
Just to give an example of how no one actually knows how many joints we have (since the definition of joints itself has no consensus), here are a few sources...
In the book Anatomy and Physiology, written by Ph.D. in Biological Sciences Blair Fraser, and Professor Emeritus of Biology Bev Lott, it is mentioned that the human body has 400 joints:
The medical practisioners working at Adventist Health hospital also claim the human body has over 400 joints:
The university of michigan health department claims the number of joints is around 300:
In a paper published last year in the prestigious National Centre for Biotechnology Information, it is also claimed that the number of joints in the human body is around 300:
The orthopedic institute of henderson claim the human body has between 250-350 joints
A children's website run by the Arthritis & Osteoporosis organisation of Western Australia also teaches a similar range of 250-350 joints:
On 'Ask a Biologist', a QnA website hosted by The Palaeontological Association, a question about joints is answered by Professor David Wynick from University of Bristol, where he once again gives a similar range from 250-350 joints
Dr Nikota Vizniak claims there are around 472 joints in the human body:
Also, According to Dr. Nikita A. Vizniak, the number 360 is outdated. Instead, he proposes ~472 joints as the answer and asserts that he and his team are the first in history to accurately name all the joints. On the product page of his book Muscle Manual, it states: “Multi-disciplinary Peer Reviewed (AT, DC, DO, LMT, MD, ND, PhD, PT, RMT)”. In a YouTube video, Dr. Nikita displays the full list of joints that are found in his book (page 16) and goes through them. Link to the video: https://www.youtube.com/watch?v=3EGwlh2XHRg&t=2s
Notably, even those who went with 360 as the answer in the past do not claim it is a fixed number, which would seem to contradict Muhammad who said "Every one of the children of Adam has been created with three hundred and sixty joints." and “A human being has three hundred and sixty joints”. "Although you might assume that the number of joints in the adult human body is fixed (at 360), this is not the case. The manual physician needs to be aware that up to one patient in 20 will have been born with extra or fewer joints than normal. This is particularly true in and around the vertebral column (…)" [Essential Physics for Manual Medicine, Martin Young, 2009, p. 73].
The Hadith also mentions "every human among the children of Adam..." so this means that both boys and men have 360 joints, but this is not the case, only adults have 360 joints, not children.