The answer is two-fold.
If pain levels are under control, a specific strength regime is necessary to strengthen not only the muscles surrounding the joint, but also muscles further away from the joint. By having stronger and more effective muscles, this will reduce the load going through our joint/s, and can also encourage improved movement patterns for the whole body.
In the knee joint for example, it is important for us to not only look at the strength of the quadriceps and gluteal muscles, but also the muscles around the trunk and ankle. The stronger we can get all these muscles, the better functioning the knee will be, which can then reduce further degeneration of the knee.
The second reason strength exercises are also important is to help manage weight. Excess weight causes increased load through the weight bearing joints. By improving your muscle mass, you will be burning more calories even when you aren’t exercising, which will help with weight management. That sounds pretty good to me!
Strength exercises could actually just using be your own body weight as a start.
It is normal to have some muscle soreness after lifting weights, but we certainly do not want your pain levels worsening.
If you are interested in commencing strength exercises, it is important to seek advice from a physio or Exercise Physiologist to make sure it is tailored, and specific to your body.