I was out for lunch one day when I felt an excurating pain in my left hand eblow. I could barely lift my outstrechted arms. The pain is concentrated to the outer area of the elbow. This muscles which are exposed only if the arms are outstrected.
You do confuse me a little with your last statement, "This muscles which are exposed only if the arms are outstrected", as the lateral side of the elbow is always out in the open. The lateral side (or outside) of the elbow is away from the body.
However, you state that the pain is concentrated on the outer area of the elbow, which is the lateral aspect. Problems on the lateral side of the elbow often involve the muscles that attach to the lateral epicondyle. These muscles are responsible for extending the wrist and fingers (straightening the wrist out and pulling it back).
This is a common place to have problems. It is often called lateral epicondylitis or tennis elbow. This is a tendonitis type of problem.
However, if this is not where your pain is located, then there are several other things that could be causing it. If the discomfort does not go away within a few days, then you may want to see your physician. Good luck.