Hello LizRo and welcome to NeuroTalk.

Your symptoms could be related to just about anything and testing will help narrow the field of possibilities.

A lack of leg strength could be as simple as a lack of exercise and strength building. It's possible you might have a mechanical back problem such as spinal stenosis, bulging/herniated discs, etc.

It takes very little time to lose strength. Depending on a cause Physical Therapy can be a good option for regaining strength and mobility, but please get the advice of a Physician before seeing a Physical Therapist.

Best wishes on your upcoming EMG.