You are in a difficult predicament. The reason why there is a reluctance to perform joint replacement surgery on you is mainly due to your age. Our research shows us that younger patients do not do well with arthritis. The first step is to determine how bad your knee is. I am guessing from what you have written that you have had key hole (arthroscopic) surgery in your knee. This will show how bad the arthritis is, and for a younger patient, is usually all that is required - especially if it is just meniscal. Arthroscopy of the knee does not help with established arthritis.
A partial knee replacement is also called a Unicompartmental knee replacement. Your knee has 3 compartments. In 9 out of 10 cases, the compartment that is diseased is the medial compartment. If the other 2 compartments are preserved, then a unicompartment replacement is suitable.
The reason why it is not preferred is that it has a much higher rate of revision than total knee replacement. Total knee replacement has a revision rate of around 7.2% at 14 years, whilst it is 20.5% at 14 years for a Uni. This is even worse if you are under 55. You revision rate jumps to 31.8% at 14 years. This is all Australian data. You are a long way from 55.
In some cases, knee replacement surgery can be considered in young patients in severe situations. Each cases needs to be fully assessed to ensure that your surgeon is doing the correct thing by operating on you. Your back does not help you symptoms, and the one danger here is if your back is contributing a lot to your knee symptoms. It may take some time to work out which element causes you the most issue, but at the end, the right decision needs to be made.
I hope this helps to answer your question.