This is Dr Basu, experienced Internal Medicine Specialist.
I am here to address your concerns and provide great service.
Indeed this is different from knee issue.
THis is lkely due to the nerve compression at the lower supplying the knee and lower leg.
So Lumbar radiculopathy is the likely cause.
Herniated disc, spine arthritis are such causes.
You can try over the counter Ibuprofen ( Advil) 2-3 tablets with food every 8 hours for pain control.
Also Warm compress and ice pack will help.
Please consider physical therapy as that will help to strengthen the back muscles and also traction to release pressure on the nerves.
Prescription medications Ketorolac, Gabapentin, Nortriptyline, Baclofen can be tried.
Please go to this link for lower back exercises:
But first see your doctor for a clinical evaluation as well.
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