soft tissue damage

quote Keiichi

The popping and locking is a strong indication of cartilage damage, which can cause further soft tissue damage over a long period of time.

The situation as you describe it would indicate that there is some significant deterioration of muscle tissue around the knee. However, despite the strain that it carries routinely, the knee is an intricate and delicate structure, and trying to self-diagnose knee problems is not the best of ideas.

There is very little that you can do yourself to correct the problem. It would appear from what you have indicated that you should seek further medical evaluation. Strengthening exercises may be as some value, so long as you use the correct exercises, but there may be need for arthroscopic repair of cartilage, tendons or other structures in the knee.

You really need an orthopedic specialist's advice.