Boy, Miriam, I sure know what you are talking about. When I go to the doctor, they either don't know what is causing the problem or they do know and there is nothing they can do about it. I have seen many doctors in my lifetime and that's happened with nearly all of them.
Because of what I just told you, I don't rush to the doctor. If that happened to my knee, I would stay off the elliptical, perhaps never get on it again depending how my knee felt. I'd start out walking around my home and then, if the knee felt fine, I would venture outside with the cane but wouldn't go far the first day to see how my knee reacted. If all was fine, I would go a little further the next day, etc. I'd use the cane for awhile until I had confidence again. I've had my knee kick in with pain before...sometimes when I'm out walking....and I end up shuffling home. So now, if I have any problems with the knee, I take my cane with me until I'm sure it's better again.
I sure am not a doctor but that's what I would do. You need to make up your own mind because you are the only one that knows how you are feeling. If you are concerned about it, definitely head to the doctor.
God does not give us a spirit of fear, but of power and of love and of a sound mind. 2 Timothy 1:7