pain after climbing stairs

hello i had a total knee replacement 4 months ago at age 56. every thing is fine except if i walk up and down the stairs a few times at home a little while later while I'm walking around i start getting a very sharp pain in my lower right back and front knee that was replaced some times it makes me come to a halt its that painful it happens when i lift my foot and knee to walk any one had the same problem?

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aha went to physio yesterday told him about my problem. before my op i had a rope made for my stair wall so i had grips on either side to hold on to whilst climbing thought it was a good idea, no no big mistake he pointed out i was probably pulling myself up the stairs and leaning to go down which is absolutely correct. He recommended i start walking up and down without using any rails, and its probably due to a trapped/tight nerve which will get better in time if i start walking down stairs normally, so thats what I've been doing along with some new stretching exercises feel better already. Thank you to my physio