Knee problem after a long period not exercising

Greetings to all reading,

I have recently got back to training and getting myself into shape. I have been quite inactive for a period of about 4-5 years (I know im lazy!). I am now 26 and upto the age of 21-22 I was very active and played a LOT of basketball (mentioning this as it's a knee problem). During this time I never had a serious injury that needed attention (just a stubbed finger or a slight sprain on the ankle) and after a week or 2 of rest, the problem always subsided and I was fine to go back and carry on as usual.

So last week I signed up to a gym and after 2 weeks I'm getting soreness in the outer ligament of the hamstring connecting at the back of the knee, on both legs.

The first sign of this problem was when I was on the bike and I felt a small pull in my left knee, so I stopped immediately and tried to stretch it out. It felt ok, but I didn't continue to exercise, just came home. The day after it was sore so I rested about 3 days, and the pain went away. Went back to the gym yesterday and it popped up again, this time in both knees. Could this be damage caused from all those years of basketball when younger? Is it that i've been quite sedate for 4+ years and I need to strengthen my ligaments?

Any advice is much appreicated as I am really eager to lose a few pounds without causing some serious damage to myself!

It's not a ligament that joins to the knee from the hamstrings. it would be a tendon. Your describing pain on the outside of your knees... It could be your ITB? this is a common sporting injury and can occur with beginning a new exercise regime, though it's not often associated with biking.
Other ways to loose weight that aren't as harsh on the joints (though biking really isn't) would be swimming. A brilliant exercise that makes you feel good.
To clarify exactly what the problem is invest in some physio - it's only recent pain and came on with starting exercise so it could be from your previous higher levels of activity but also could be something different and easy to fix with a bit of guidance.
Let us know how you get on.