About 2 Weeks Ago I Pulled What I Thought Was

about 2 weeks ago i pulled what i thought was a muscle in my lower back by just walking down a stair. i felt a click and then had instant pain. But now i have pain in my knee and hip joints and i can hardly walk some days as my ankles and feet are in chronic pain. im only 35 and i am of average build so im not putting extra pressure on my joints due to my weight. the pain is so bad in my feet and ankle bones. I have always been an active person and am not doing anything extra than normal and i have good supportive shoes. I tried rubbing Deep heat and antiflamme into my feet (iboprofen and menthol based products) but it hasnt worked. Any suggestions on what it could be? Thank you