This sounds like a problem with the spinal cord. A decreased sensitivity along the entire one side of the body, including the leg and foot has to occur due to a problem in the central nervous system - either the brain or the spinal cord.
The fact that you can lift your arm over the head shows that your shoulder joint is all right. But the inability to lift heavy loads and being unable to open medicine bottles indicates muscle weakness.
I feel that you need to consult an orthopedist again - you need to get a test called a myelogram. This is a special xray which can identify the spaces in the spinal cord and if there is any stenosis. This may not show up clearly in a simple xray and MRI scan.
You also need to get a nerve conduction velocity test of the two main nerves of the arms as well as a muscle biopsy. These tests will show up if you have a nerve problem in the spine or a muscle weakness like a dystrophy.
I hope this helps.
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Experienced in the management of Pregnancy,Infertility,Menopause and all problems in Pregnancy and Gynecology