The correct spelling is A-R-T-H-R-I-T-I-S

Arthritis is spelled with eight letters: A-R-T-H-R-I-T-I-S. The word comes from Greek roots meaning "joint" (arthro-) and "inflammation" (-itis). It's one of the most commonly misspelled medical terms because the "th" combination and double "i" near the end trip up many people, even those who have lived with the condition for years.

If you're looking up arthritis for medical forms, insurance paperwork, or doctor's notes, use this exact spelling. Medical records systems are literal—a misspelling won't match your actual diagnosis in the database, which can cause delays when requesting records or switching providers. Getting the spelling right the first time saves you from having to correct it later.

Key Takeaways

  • Arthritis is spelled A-R-T-H-R-I-T-I-S, with the "th" digraph in the middle and two i's near the end.
  • Common misspellings include "arthritus," "arthitus," and "arthuritis"—all of which will not match medical records systems.
  • When filling out medical forms or insurance documents, copy the spelling directly from your diagnosis letter to avoid record-matching problems.
  • Related terms like "osteoarthritis" and "rheumatoid arthritis" follow the same base spelling with prefixes added.
  • If you've already submitted a form with incorrect spelling, contact the office to request a correction in their records.

Common misspellings and why they happen

The most frequent mistakes are "arthritus" (dropping the second "i"), "arthitus" (removing the "h"), and "arthuritis" (changing the "a" to "u"). These happen because the word doesn't follow common English patterns—the "th" is unusual in the middle, and the ending "-itis" is a medical suffix that people often mishear or misremember when they hear it spoken aloud in a doctor's office.

Another common error is "arthritis" with only one "i" at the end, written as "arthrits." This usually occurs when someone is typing quickly or relying on muscle memory from a word they've seen but not carefully studied. The double "i" is easy to overlook because the two letters blend together visually, especially in handwriting or on a small screen.

People also sometimes write "arthritis" as "arthritus" because "-itus" sounds like a plausible medical ending, even though the correct suffix is "-itis." This confusion is understandable—many medical terms do end in "-itis"—but arthritis specifically requires the "i" before the "t."

Spelling related arthritis types

When you add a prefix to arthritis, the base spelling stays the same. Osteoarthritis is spelled O-S-T-E-O-A-R-T-H-R-I-T-I-S. Rheumatoid arthritis keeps arthritis as A-R-T-H-R-I-T-I-S, with rheumatoid spelled R-H-E-U-M-A-T-O-I-D before it. Your diagnosis letter will show you exactly which type you have.

Other variants follow the same rule: juvenile arthritis, psoriatic arthritis, septic arthritis, and gout-related arthritis all use the correct A-R-T-H-R-I-T-I-S spelling at the end. If you're unsure about the prefix, focus on getting "arthritis" right—that's the core term your doctor will be looking for in your records. The prefix just narrows down which kind of arthritis you have, but the base word is always spelled the same way.

Where spelling matters most in your medical care

Medical records systems search by exact spelling. If you write "arthritus" on an insurance form and your diagnosis is recorded as "arthritis," the system may not match them. This can delay approval for treatments, create gaps in your medical history when you switch providers, or cause confusion when your records are transferred to a specialist who needs to see your full background.

When filling out any official form—insurance paperwork, disability claims, new patient intake, or referral requests—copy the spelling directly from your diagnosis letter or previous medical records rather than typing from memory. Most forms also have a space to paste or reference your diagnosis code, which bypasses spelling altogether and is the safest option if available.

How to remember the correct spelling

Break the word into parts: arth (joint) + ritis (inflammation). The "th" is the trickiest part because it's not pronounced clearly in casual speech. Say it slowly: "arth-RY-tis." The "th" is there even though it's easy to skip over when you're speaking quickly or not paying close attention to pronunciation.

Another memory trick: the word ends in "-itis," which is the standard medical suffix for inflammation. Once you know that pattern, you know arthritis must end with two i's (one from "arth" and one from "itis" running together). Think of other "-itis" words you may know—bronchitis, gastritis, tendinitis—and you'll see the pattern holds across medical terminology.

Checking your spelling before submitting documents

Before you submit any form with "arthritis" on it, use the find-and-replace function in your word processor to search for common misspellings. Type "arthritus" and see if it appears—if it does, replace it with "arthritis." Do the same for "arthitus" and "arthuritis." This takes less than a minute and catches errors you might miss when reading through the form once.

If you're handwriting a form, write it once on scratch paper first and check it against this guide. Take a photo of the correct spelling on your phone so you can reference it while filling out paperwork in a doctor's office or at home. You can also write "A-R-T-H-R-I-T-I-S" on a sticky note and place it near your workspace while completing medical documents.

What to do if you've already submitted incorrect spelling

If you've already submitted a form with "arthritus" or another misspelling, contact the office or organization that received it and ask them to correct the spelling in their records. Provide your correct diagnosis and the form you submitted. Most places can update records without requiring you to resubmit the entire form, though the process may take a few business days.

Keep a record of when you requested the correction and who you spoke with. If you later notice the misspelling is still in the system, follow up again with that person or ask to speak with the records department directly. Getting it fixed early prevents problems down the line when your records are shared between providers.

Frequently Asked Questions

Is it "arthritis" or "arthitus"?

It is always "arthritis" with an "h" and two i's. "Arthitus" is a common misspelling that will not match your medical records. Use A-R-T-H-R-I-T-I-S on all official documents.

How do you spell osteoarthritis?

Osteoarthritis is spelled O-S-T-E-O-A-R-T-H-R-I-T-I-S. The base word "arthritis" stays the same; "osteo" (meaning bone) is added at the beginning. Check your diagnosis letter to see which form your doctor uses.

Does the spelling change for rheumatoid arthritis?

No. Rheumatoid arthritis is R-H-E-U-M-A-T-O-I-D A-R-T-H-R-I-T-I-S. The "arthritis" part is always spelled the same way, regardless of what type of arthritis you have.

What should I do if I already submitted a form with the wrong spelling?

Contact the office or organization that received it and ask them to correct the spelling in their records. Provide your correct diagnosis and the form you submitted. Most places can update records without requiring you to resubmit the entire form.

Will a misspelling affect my medical care?

It can delay things. Insurance systems, specialist referrals, and medical record transfers rely on matching your diagnosis exactly. A misspelling might cause the system to flag your records as incomplete or create a duplicate file, which slows down approvals and transfers.