When you are relying on medication to get you through the day it is important to have a good understanding of what is safe. There is no substitute for trained medical advice that is specific to your medical history. None of us are the same and some drugs work better for some people than they do for others.
Again, having a basic understanding can help you ask the right questions.
Paracetamol is a common arthritis drug. Many people do not give it credit as it is readily available over the counter but studies have shown it to be effective in treating arthritic pain. It has relatively few drug interactions and side effects but it is important to stick to the recommended amount as the overdose level is not particularly well distanced from the therapeutic dose.
NSAIDs or Non Steroidal Anti-Inflammatory Drugs are also typically used to combat arthritic knee pain. Many of these drugs are also available over the counter. They do have some common side effects to be aware of such as exacerbation of asthma and gastrointestinal tract bleeding. They should always be taken after food for this reason. Aspirin is a member of this family of drugs. It is usually safe to take these drugs in combination with paracetamol.
Opioids are another category of common knee arthritis medications. Codeine (a.k.a. Tylenol 3) is often sold as a combined preparation with paracetamol. Codeine is a strong pain killer but can have serious consequences if overdosed and can cause constipation even at recommended levels. Care should be taken combining any codeine product with paracetamol as it is so common for the codeine tablet to contain paracetamol that any additional paracetamol can lead to overdose and liver damage.
If you are not happy with the relief your current analgesia is delivering, discuss your options with your physician or pharmacist. Get specialist advice as the interactions between drugs are extremely complicated and your personal medical history needs to be taken into account. Some drugs can be combined to give extra relief but this process needs to be overseen by a professional.