ICD-10 Code M05.859 – Other rheumatoid arthritis with rheumatoid factor of unspecified hip (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code M05.859 – Other rheumatoid arthritis with rheumatoid factor of unspecified hip
What it is
This code identifies rheumatoid arthritis with rheumatoid factor affecting the hip, when the hip side is not specified. It is used for a rheumatoid arthritis subtype that does not fit a more specific hip category.
Clinical signs
Typical findings include chronic joint pain, stiffness, swelling, and reduced range of motion in the hip. Clinical features vary; refer to documentation for rheumatoid factor positivity and the affected hip.
When to use this code
Use this code when the record documents rheumatoid arthritis with rheumatoid factor and names the hip as involved, but does not identify right or left. It also fits cases labeled as other rheumatoid arthritis with rheumatoid factor when the hip is the documented site. Check documentation if the note is unclear.
Do not use for
Do not use it for rheumatoid arthritis without rheumatoid factor, or when the documentation specifies another joint only. If the side of the hip is documented, choose the more specific code.
Coding tip
Confirm both rheumatoid factor involvement and an unspecified hip before assigning M05.859.