Each branch can choose its own fate, but only those that commit to fundraise, campaign, or provide information can remain part of the charity - these branches will be known as 'charter' groups.
Other branches can choose to become 'affiliated independent' groups, receiving their running costs for two years, or become fully independent, severing their connection to Arthritis Care; neither can use the charity's name.
Director of communications Kieran Kettleton said the move is prompted by "new strategic objectives and the need to protect trustees in an increasingly litigious society". Under the current structure, trustees are liable for any incidents at branches.
On 17 January, the charity's south-east regional committee wrote to the board to complain that the new structure had been decided without consultation.
It said: "It is proposed that branches that confine their activities primarily to arranging social events should leave the charity and set up their own organisation outside Arthritis Care. As such groups provide a network for vulnerable people with arthritis to get access to information and support services, we suggest that there should be a category within the charter groups to allow them to remain within the charity. Such branches need back-up services such as public liability insurance and the use of the charity's name when applying for grants."
Kettleton said the final 'charter' definition was yet to be finalised.
But many members believe the real issue is money, and have vented fury at the proposals in an online forum. Charles Lee from the Wirral accused the charity of "gambling with a potent membership base on the chance of a cash injection to central funds".
Fiona Blackburn from Glasgow Central added: "It seems that after its incompetence it has taken the easy way out by appropriating branch funds ... the fact it is trying to dress this up as the fault of wealthy branches hoarding money and not using it to the benefit of all people with arthritis is pathetic."
In a letter to branches last month, chair Terry Oliver said: "According to law, we have to give full account of the money that belongs to the charity (including branch funds) and demonstrate that it is being used to deliver our key services. The need to balance the interests of branch members and all people with arthritis is paramount."
Kettleton said the charity would meet every branch separately to discuss the options.