1. The first time
The first time John fell and he blamed Sherlock for it he was in some ways also a little grateful for it.
The morning after the solution to the taxi driver case found him waking up elated but aching. Running like that after months of limping around London with that bloody cane had been liberating. Now however he was paying the price for it. His muscles ached where he had twisted them into new configurations and his leg was genuinely painful to stand on. Yes, of course it was mostly psychosomatic but at one point the wound had been there and with the return of the limp after his return to England his already damaged muscles had begun to atrophy which had not been aided by his unwillingness to actually put weight on them.
Still after the previous evening there was no way that he was going to go back to using that blasted stick. He would not suffer the indignity of Sherlock seeing him resorting to it again, so he forced himself out of bed and tried to make his way down the stairs to the bathroom without it.
With only three steps left his body betrayed him and the leg just buckled under him. He fell bonelessly down the last three steps landing with a resounding thump on the floor beneath the stairs. He lay there for a minute catching his breath and cursing his damn leg as very real pain pulsed from his knee to his hip making him clench his teeth against it.
Sherlock appeared from the living room with a puzzled look on his face. "What happened? Are you okay?" He asked as he crouched down beside his new flatmate.
"Fine!" John spat out as he sat up rubbing at the offending limb.
"Hm…" Sherlock looked thoughtful, "I was right… not entirely psychosomatic, but mostly. You probably should not go cold turkey on that cane of yours" he deduced and stood extending his hand to John.
"Now you're telling me. This is all your fault for making me feel self-conscious about it in the first place." He grumbled as he accepted the hand and stood before limping into the bathroom to search for paracetamol.
Sherlock stood watching him go. He really didn't get sentiment. John had gone from limping constantly to only limping after overexerting himself, all thanks to Sherlock, so what on earth was he blaming him for. He would have thought that thanks would have been in order. Strange things feelings… he would need more data before he could make any deductions about that. With that he left John to his grumbling in the bathroom and returned to the living room and his current experiment.