It is very common for people with arthritis to experience symptoms in their knees and Hip, so you are not alone in this. As you already know, loosing weight (if you are still over weight) and strength exercises are really important to help you to prepare for surgery.
There is a common misconception that if you have arthritis, exercise is somehow bad for you. In reality so long as you are careful and build up slowly, for most people this could not be further from the truth. Research shows that becoming more physically active is extremely beneficial for those with arthritis. Strengthening the muscles in the front of the upper leg (the Quadriceps) has been proven to reduce the pain of knee arthritis in many people. Simple stretching exercises can help to improve the flexibility of the joints. Doing general exercises that helps to keep the heart and lungs healthy can reduce the progression of the condition in many cases and in some improve things considerable.
The charity Arthritis Action (https://www.arthritisaction.org.uk/livi ... exercises/
) provides a number of free, very easy to follow exercise fact sheets that you might want to try to start off with. For those who need a little more support, most GPs will have an agreement with a local health centre (the scheme is usually called ‘Exercises on referral’) that will offer you access to subsidised personal trainer sessions to build your confidence.
For people with knee pain specifically, there is an exercises programme called ‘ESCAPE-Pain’ (http://www.escape-pain.org/
) that has 12 years’ worth of high quality research supporting it. This programme has been proven to reduce pain, improve your ability to perform daily activities and help with some of the psychological symptoms of arthritis such as low mood. It also includes self-management education sessions to enable you to understand your condition and take control. You can even download a free App from the App store to allow you to try it out at home.
To reassure you about the possibility of there being something more going on or if you feel that you need support from a medical professional, manual therapy such as osteopathy has also been proven to help in many cases, especially for knee arthritis. You can book a private appointment with an osteopath without the need for a GP referral. You can find your nearest osteopath at https://members.iosteopathy.org/find-an-osteopath
You can also find an excellent YouTube video about preparing for hip or knee surgery at https://www.youtube.com/watch?v=xAL_TrQdtTY&t=7s
Best of luck,