ICD-10 Code for Knee Osteoarthritis

Also searched as osteoarthritis of knee, knee oa

The ICD-10-CM code for knee osteoarthritis depends on the side: M17.11 for the right side, M17.12 for the left, M17.0 for both sides and M17.10 when one side is affected but the record does not say which. M17.9 applies only when the record does not say whether one side or both are affected. If the record documents a more specific type, the code changes — see the qualifiers below. Valid for FY2027.

M17.9 billableLaterality requiredUnspecified

Knee osteoarthritis ICD-10 codes at a glance

Condition	Knee osteoarthritis
Right	M17.11 — Unilateral primary osteoarthritis, right knee
Left	M17.12 — Unilateral primary osteoarthritis, left knee
Bilateral	M17.0 — Bilateral primary osteoarthritis of knee
Unspecified	M17.10 — Unilateral primary osteoarthritis, unspecified knee
Billable	Yes (M17.9)
Alphabetic Index entry	Osteoarthritis, knee
Code set	ICD-10-CM FY2027, valid October 1, 2026 – September 30, 2027

What is the ICD-10 code for right knee osteoarthritis?

The ICD-10-CM code for right knee osteoarthritis is M17.11 — Unilateral primary osteoarthritis, right knee. M17.11 is billable.

What is the ICD-10 code for left knee osteoarthritis?

The ICD-10-CM code for left knee osteoarthritis is M17.12 — Unilateral primary osteoarthritis, left knee. M17.12 is billable.

Is there an ICD-10 code for bilateral knee osteoarthritis?

Yes. The ICD-10-CM code for bilateral knee osteoarthritis is M17.0 — Bilateral primary osteoarthritis of knee. M17.0 is billable.

“When a patient has a bilateral condition and each side is treated during separate encounters, assign the "bilateral" code (as the condition still exists on both sides), including for the encounter to treat the first side.”
ICD-10-CM Official Guidelines, Section I.B.13

“For the second encounter for treatment after one side has previously been treated and the condition no longer exists on that side, assign the appropriate unilateral code for the side where the condition still exists (e.g., cataract surgery performed on each eye in separate encounters). The bilateral code would not be assigned for the subsequent encounter, as the patient no longer has the condition in the previously-treated site.”
ICD-10-CM Official Guidelines, Section I.B.13

When can the unspecified-side code for knee osteoarthritis be used?

The unspecified-side code for knee osteoarthritis is M17.10 — Unilateral primary osteoarthritis, unspecified knee. M17.10 is billable.

“If the side is not identified in the medical record, assign the code for the unspecified side.”
ICD-10-CM Official Guidelines, Section I.B.13

“Codes for "unspecified" side should rarely be used, such as when the documentation in the record is insufficient to determine the affected side and it is not possible to obtain clarification.”
ICD-10-CM Official Guidelines, Section I.B.13

What changes the knee osteoarthritis code?

The Alphabetic Index lists these qualifiers under Osteoarthritis, knee. If the record documents one of them, the code changes. Verify the code in the Tabular List before reporting it.

bilateral	M17.0	Bilateral primary osteoarthritis of knee
bilateral › post-traumatic	M17.2	Bilateral post-traumatic osteoarthritis of knee
bilateral › secondary	M17.4	Other bilateral secondary osteoarthritis of knee
primary	M17.1-	Unilateral primary osteoarthritis of knee
primary › bilateral	M17.0	Bilateral primary osteoarthritis of knee
unilateral	M17.1-	Unilateral primary osteoarthritis of knee
unilateral › post-traumatic	M17.3-	Unilateral post-traumatic osteoarthritis of knee
unilateral › primary	M17.1-	Unilateral primary osteoarthritis of knee
unilateral › secondary NEC	M17.5	Other unilateral secondary osteoarthritis of knee

What does the Tabular List say about M17.9?

The instructional notes that govern M17.9, including those it inherits from its category and chapter. An Excludes1 note means the two codes are never reported together.

Excludes2 — not included here — inherited from Chapter 13

The conditions below are not part of M17.9, but a patient may have both at the same time. When documentation supports it, M17.9 and the excluded code may both be reported.

arthropathic psoriasis (L40.5-)
certain conditions originating in the perinatal period (P04-P96)
certain infectious and parasitic diseases (A00-B99)
compartment syndrome (traumatic) (T79.A-)
complications of pregnancy, childbirth and the puerperium (O00-O9A)
congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
endocrine, nutritional and metabolic diseases (E00-E88)
injury, poisoning and certain other consequences of external causes (S00-T88)
neoplasms (C00-D49)
symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Excludes2 — not included here — inherited from M15-M19