The former Leeds and England captain helped raise more than £2 million from a gruelling 101-mile run from the home of his current club, Leicester Tigers, to Headingley in November - the equivalent of almost four marathons, completed without sleep inside 24 hours.
In December 2020 he ran seven marathons in seven days, which generated £2.7 million in donations.
After a Windsor Castle investiture ceremony hosted by the Duke of Cambridge, Sinfield said: "I think to be able to keep MND in the spotlight and continue to give it the awareness it deserves has been really special, so I'm delighted to be here to accept the honour on behalf of the whole of rugby league and MND community.
"Rob's story and his courage and his bravery has really inspired people, and whilst he's willing to fight like he is, as a former teammate and a friend it's really important, like we did on the rugby field, we stick together now.
"It's lovely to be recognised myself but there's been so many other people involved.
"The two big challenges we've done, our team have been magnificent - I think it's really important for the MND community we keep banging the drum.
"But then you see the awareness and funds that the support has created - which is wonderful - and the sport of rugby league absolutely got behind it and got behind Rob."
For his 101-mile challenge Sinfield was given a send-off in Leicester by the Coldstream Guards and received good luck messages from fellow sports stars Alan Shearer, Ian Wright and Mo Farah.
Speaking about the effects of the run on his legs, he added: "They were pretty sore, but it was worth every step.
"Just the support and the camaraderie between the team was really special and during the journey of doing the two challenges we've created some amazing memories for each other and it's been great being back in a team."
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