The problem isn’t with the last syllable. The “i" in the second syllable of the word “tinnitus” is short, and the “i” in the second syllable of the word “arthritis” is long. That’s why the rhyme doesn’t work. Also, the first syllable in “tinnitus” is stressed, whereas the second syllable in “arthritis” is stressed, so the lines also fail to scan properly.
The problem isn’t with the last syllable. The “i" in the second syllable of the word “tinnitus” is short, and the “i” in the second syllable of the word “arthritis” is long. That’s why the rhyme doesn’t work. Also, the first syllable in “tinnitus” is stressed, whereas the second syllable in “arthritis” is stressed, so the lines also fail to scan properly.