Neuropathic Pain - I've been taking gabapentin for nerve pain in my knee but it's not helping.

The answer to your question depends upon several things.
Have you seen a doctor about the nerve pain in your knee? If so, has your doctor diagnosed the cause of the pain?
Gabapentin, which I take, is primarily used for neuropathic pain from nerve damage or disease. It is not particularly useful for nerve pain caused by other factors, such as a pinched or trapped nerve.
I would suggest giving it 3 to 4 weeks and, if your pain is caused by neuropathy, you may need to have your dose adjusted a little at a time until you reach the dosage that works for you.
If you ultimately find that Gabapentin does not work at all for you, I strongly urge you not to take Ibuprofen for long-term pain, only acute pain such as one caused by an injury. Ibuprofen should not be taken for long periods of time.
If you have not been diagnosed, I recommend working with your doctors using Imaging technology to discover the cause of your pain. It is possible that there are other treatments that could be more effective, such as an injection or surgery, depending upon what the findings are.
I have peripheral neuropathy, worse in my right arm than my left, and 300 mg of Gabapentin three times a day relieves me of my neuropathic pain. Fortunately, the lowest dose works for my pain.
For my arthritic pain, I take 1,000 mg of acetaminophen twice a day. I never take Ibuprofen or other NSAIDs as they ultimately cause kidney damage taken long-term.
In a nutshell, I would give the Gabapentin three to four weeks, and then continue to increase the dose if it's not working. But be warned that Gabapentin can cause drowsiness, especially in higher doses. And I would advise not to take Ibuprofen or any other NSAID for chronic, long-term pain.