Early stages of Osteoarthritis

It happened about 6 months back
when I felt some tightness and pain
in the second and third fingers of my left hand.

The pain only aggravates when I grasped my
fingers .... and it revolves around the joints.

And if I don't curl in the fingers, then I would
not feel any pain at all.

Being an exercise fanatic, my initial thought
was that the tightness and pain could be due
to the dumbbell weight-lifting routines that I
was doing .... and perhaps due to the push-ups
exercises since the entire body weight was
focussed on the fingers of my two hands.

.... as the pain was bearable and not a matter
of life and death to me ..... I just let it be ....

Moreover, the discomfort at the joints tend
to move around !!

From the second and third fingers, it soon
expanded to the fourth finger. Yet several days
later, it subsided gradually ..... and suddenly,
the pain progressed onto my right hand.

For the next 3 months, the irritating pain and
tightness of the finger joints tend to flip from
one hand to the other hand, and vice versa.

I tried my best to cope with it, consoling myself
that this is just a seasonal and temporary muscular
problem .... that it will soon disappear by itself ....
until one day, I decided to seek medical help
..... only to be told that I have osteoarthritis !!

How can a healthy 48 year old be diagnosed
with osteoarthritis in hands ....... or osteoarthritis
of hands ?