Okay, so I work in medical device manufacturing most of my adult life and I actually machined knee joints about 25 years ago. Very few of the engineers, technicians, tradespeople or QA people I've worked with in a career spanning more than 30 years supplying multinationals in Ireland, Europe and the USA have been members of a professional body and none of them have required that accreditation in order r to do their job.As an engineer I can say with confidence that for amoral as well as moral reasons that nobody without the proper qualifications and institute memberships/chartered status/etc would be taken into a position of quality responsibility in a medical device manufacturing plant. NASI auditing quality standards isn't much use if piles of individually expensive artificial knees have been churned out and passed quality checks in the meantime: the potential financial loss is too high.
I've been part of customer R&D teams and Design Teams, I've lead process development teams, developed process validation procedures, worked as a QA Engineer maintaining both ISO 99001 and 13485 quality management systems (that required training and certification only), worked as a CAD engineer and programmer, introduced LEAN, and served my time as a Toolmaker. I can say emphatically that no one involved in ensuring the quality of the products we've produced has ever required membership of a professional body, neither have any of the engineers I've worked with within my MNC customers.
Those engineers had Masters and PhD's and were brilliant engineers from all over the world. Their employer cared firstly about their experience and ability and secondly about their qualification. Nobody cares about whether they are members of a professional body. That all seems very anachronistic.