All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
Dear brother, you should know that anything that comes from Allaah The Almighty or from the Prophet, sallallaahu ‘alayhi wa sallam, must be believed in without reference or verification from humans.
The statement of the Prophet, sallallaahu ‘alayhi wa sallam, that every human is created with 360 joints in his body is a Hadeeth (narration) narrated by Imaam Muslim. Having known that the Prophet, sallallaahu ‘alayhi wa sallam, said it, we must believe in his statement without asking questions, because everything he said was inspired by Allaah The Exalted. Allaah The Almighty Says (what means): {Does He who created not know, while He is the Subtle, the Acquainted?}[Quran, 67:14]
With regard to the scientific aspect of the Hadeeth, you may refer to specialists in case you want to convince a non-Muslim by engaging him with knowledge on Quranic and Prophetic scientific miracles. It is enough for a Muslim, however, to be convinced with the authenticity of the Hadeeth. If scientists advocate something contrary to the statement of the Prophet, sallallaahu ‘alayhi wa sallam, their results are to be rejected because the Prophet's, sallallaahu ‘alayhi wa sallam, sayings are true and theirs are not absolutely correct.
Misunderstandings occur due to either the manner of comprehending religious texts and their significance, or the shortcomings of medical research and the extent of its information. Thus, we must take into consideration that established revealed texts are not to be doubted.
Allaah Knows best.