wel according to your other thread you want a PUPPY and arnt willing to give an older dog a thought...
a medium breed could fit any numbumber of size categories, a 25lb dog is medium...a 40lbs dog is medium, a 60lb dog to some is a medium sized dog...
so heres some ideas.
im going to list breeds with low-medium energy levels, due to your mobilitiy issues, this will likley rule out many working breeds and terriers simply because those are high energy breeds that need to run and need a job.
im also going to add that a puppy is NOT a good idea for a mobility impaired person, lots of stooping bending and ALL puppies are high energy.
so im going to suggest you look for a dog about 2 yrs old...
by this point they are still very young, still have the majority of their life ahead of them, still young enough to learn and absolutly young enough to bond to their person...
most by that age are house broken, and have at least basic training (many breeders have 2-3 yr old dogs available to good pet homes because they didnt quite pan out for show ect)
that leads to my next point...
contact brreders and ask if they do have any YOUNG dogs available to pet homes that didnt quite fit the show ring ect...
you can find an amazing pet whos often already very well trained this way!
i know you "realy want a puppy"
but you have to keep THE DOGS best interests in mind...
are you honestly going to be able to keep up with a highly energetic, mischevious dog with no manners.
are you going to be able to bend down to clean up accidents, are you going to eb able to catch puppy mid accident pick it up and get it outside to finnish up...
ect.
that all being said...
some breeds ive had experience with that MIGHT work for you given the right dog, of the right age...
American Pit Bull Terrier...these dogs are short haired and high energy as a breed generally, BUT an older already trained APBT well socilized with the right temperment match for you coule be an ideal companion, they love thier people are very attatched, inteligent and while they can be stubborn goofballs they love to please their people.
Cocker spaniel, american or english...get a rescue or from a VERY repuatable breeder to avoid the temperment issues the breed aparently has.
i grew up with cockers, the breed is supposed to be happy go lucky, merry and sweet.
lots of mills and BYBS have given the breed a reputation to bite...so be VERY diligent about finding a good breeder.
this breed is a Small-medium breed, english are bigger, long haired, easy to train (agian assuming good lines) and VERY loving (again assuming good lines).
personally i feel this gould be a great match for you as a general breed, there ower energy than most of the other spaniels, and generally while not the brightest crayon in the box they are very eager to please.
charlie loves to go for walks and have a real good run...but hes also happy to curl up next to you and snuggle.
a golden...as hard as that might be for you, a golden would be a potentially good match...
an older lab...some labs are insane, but some are sweethearts...i absolutly would NOT suggest a lab puppy though.
tibetan terrier...every one ive met have been wonderfull, on the smaller end of medium though. they do need a deacent amount of excersize but there also very adaptive to their people.
if your willing to expand your serch to smaller breeds theres a good number of small breds that would also realy suit you.