ICD-10-CM 2027
ICD-10 code for knee osteoarthritis
Confirmed by the official ICD-10-CM index entry “osteoarthritis › knee”. Page updated September 29, 2026.
About coding knee osteoarthritis
The ICD-10-CM code for knee osteoarthritis is M17.9 (Osteoarthritis of knee, unspecified). The official index lists 10 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on M17.9.
It is also searched as knee arthritis.
Within M17, choose M17.9 (unspecified) only when documentation doesn't support a more specific option: bilateral primary osteoarthritis of knee (M17.0), unilateral primary osteoarthritis of knee (M17.1), bilateral post-traumatic osteoarthritis of knee (M17.2), unilateral post-traumatic osteoarthritis of knee (M17.3), other bilateral secondary osteoarthritis of knee (M17.4) and other unilateral secondary osteoarthritis of knee (M17.5).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 553 (Bone Diseases and Arthropathies with MCC, relative weight 1.2494) and DRG 554 (Bone Diseases and Arthropathies without MCC, relative weight 0.8331), in MDC 08 (Diseases and Disorders of the Musculoskeletal System and Connective Tissue), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
Related Knee osteoarthritis codes
- M17.0 Bilateral primary osteoarthritis of knee
- M17.10 Unilateral primary osteoarthritis, unspecified knee
- M17.11 Unilateral primary osteoarthritis, right knee
- M17.12 Unilateral primary osteoarthritis, left knee
- M17.2 Bilateral post-traumatic osteoarthritis of knee
- M17.30 Unilateral post-traumatic osteoarthritis, unspecified knee
- M17.31 Unilateral post-traumatic osteoarthritis, right knee
- M17.32 Unilateral post-traumatic osteoarthritis, left knee
- M17.4 Other bilateral secondary osteoarthritis of knee
- M17.5 Other unilateral secondary osteoarthritis of knee
Common questions about knee osteoarthritis ICD-10 codes
What is the ICD-10 code for knee osteoarthritis?
- M17.9 — Osteoarthritis of knee, unspecified. More specific codes apply when the documentation supports them: M17.0, M17.10, M17.11, M17.12 and others below.
What is the ICD-10 code for bilateral primary osteoarthritis of knee?
- M17.0 — Bilateral primary osteoarthritis of knee.
What is the ICD-10 code for unilateral primary osteoarthritis, unspecified knee?
- M17.10 — Unilateral primary osteoarthritis, unspecified knee.
What is the ICD-10 code for unilateral primary osteoarthritis, right knee?
- M17.11 — Unilateral primary osteoarthritis, right knee.
What is the ICD-10 code for unilateral primary osteoarthritis, left knee?
- M17.12 — Unilateral primary osteoarthritis, left knee.
What is the ICD-10 code for bilateral post-traumatic osteoarthritis of knee?
- M17.2 — Bilateral post-traumatic osteoarthritis of knee.
What is the ICD-10 code for unilateral post-traumatic osteoarthritis, unspecified knee?
- M17.30 — Unilateral post-traumatic osteoarthritis, unspecified knee.
Is M17.9 billable?
- Yes. M17.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can M17.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict M17.9 as a principal diagnosis.
Is M17.9 a CC or MCC?
- No. M17.9 is neither a CC nor an MCC under MS-DRG v44.0.