<s>[INST] My left leg is 5 cm shorter than my right. I wear a lift in my left shoe to help even things out but my left knee has been causing serious pain. I cannot sit, kneel or do any movement that bends the knee with weight. I can bend while sitting without pain, just popping. What should I do? [/INST] Thanks for your question on Chat Doctor. I can understand your concern. You are having left lower limb shortening. So pathological osteoporosis, osteoarthritis are more in left lower limb joints (especially knee joint because it is the most weight-bearing joint). Shoe lifts and other things are temporary measures. On long run, osteoporosis and osteoarthritis are bound to occur which cause pain on weight-bearing positions. So consult orthopedic doctor and get done clinical examination of left knee and x-ray left knee. You will need calcium, vitamin D3 supplements, physiotherapy and knee replacement (if osteoarthritis is severe). Hope I have solved your query. I will be happy to help you further. Wish you good health. Thanks. </s>