<s>[INST] Hi there, I was walking today and then suddenly my left leg started feeling weird. It feels like there s a bubble in the knee area of the leg. For instance, when I bend and straighten my leg it feels like I can feel the muscle.....I m not really sure how else to describe it? [/INST] Hi, I value your concern regarding the symptoms. I have gone through your symptoms, and in my opinion you will be having either meniscal tear, or some joint swelling. If it is painful and bothering you, it needs to be seen by or tho doctor, and investigated accordingly. Hope this answers your question. If you have additional questions or follow-up questions then please do not hesitate in writing to us. I will be happy to answer your questions. Wishing you good health. Special note-Any medication prescribed needs to be taken after consultation with your personal doctor only. </s>