Time off for Joint Replacement- Disability Leave


I am due to have a wrist replacement, however my works policy on leave covers illness/injury which I don't think covers disability leave. I have sickness due to RA and Fibro and this is being counted towards my entire sickness, its not split into separate normal sickness leave ( stomach bug etc) vs time off due to flares. Therefore I am coming up to the allocated time I am allowed off before my sick pay ceases. Having my replacement I'm presuming I will be of work for 4-6 weeks, therefore I didn't want this to be counted towards my sickness as i feel its not sickness. Does anyone know if there are any GOV/Equality Act reading i can do on this? I personally cannot find anything. How have other employers acted towards time off for joint replacements?

Many thanks