As per my understanding, you are experiencing discomfort in your waist & knee and gradual decreased sensation in your lower limbs, along with difficulty in walking as well. There are several causes which can lead to this kind of presentation. Causes generally are classified into spinal causes, traumatic causes or neuromuscular causes etc. Eg: slip disc, multiple sclerosis pinched nerve syndrome, peripheral neuropathy and many more. Treatment generally will be physiotherapy, occupational therapy, medication if required surgery but if there is weakness, difficulty in walking, or numbness, then it's a medical emergency. So kindly consult an orthopedic and a neurologist to rule out what exactly is the pathology behind your symptoms and get treated accordingly. You can also refer this page for orthopedic doctors - 10 Best Orthopedic Doctor in India, and this for neurologists - 10 Best Neurologist in India. Hoping that you get the necessary help!