Brief Answer:
Read below.

Detailed Answer:
I read your question carefully and I understand your concern.

The fact that the symptoms involve only one limb indicate that it is a question peripheral nerve involvement. That is because a central lesion in the brain would usually affect one half of the body, lower and upper limb. A central lesion in the spine also has other symptoms, such as involvement of both limbs and bladder issues.

Now regarding what kind of peripheral involvement is difficult with the little information you provide on the exact distribution of the symptoms and without being able to examine you (for changes in your reflexes, muscle strength and sensitivity, which would indicate the nerve involved). Generally speaking the most common cause would be a nerve root compressiom due most commonly to compression from a bulging of one of the discs situated between your vertebrae. If the symptoms are present only from the knee downward then it could be a compression of a more peripheral nerve, or a case of polyneuropathy (though polyneuropathy commonly involves both limbs).

So to make a diagnosis a neurological physical exam and according to findings other tests could include MRI of the lumbar spine or nerve conduction studies.

Let me know if I can further assist you.

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