Is M25.66 a billable ICD-10-CM code?

No. M25.66 is a non-billable header code. Code to a higher level of specificity using one of its child codes.

Where does M25.66 sit in the tabular list?

Diseases of the musculoskeletal system and connective tissue (M00-M99), in the block Other joint disorders (M20-M25).

What cannot be coded together with M25.66?

M25.66 carries Excludes1 notes, which means the conditions they list can never be coded together with it on the same encounter. Some are written on the categories above M25.66 (M25.6) and apply to it just the same.

M25.66

M25.66 — Stiffness of knee, not elsewhere classified

Non-billable headerICD-10-CM

M25.66 is a non-billable header ICD-10-CM code for stiffness of knee, not elsewhere classified. It cannot be billed on its own: choose one of the more specific child codes below.

Excludes1 inherited from the categories above M25.66

These are not written on M25.66, but they bind it: a note on a category applies to every code beneath it. Billing M25.66 with anything listed here is a denial.

Written on M25.6 — Stiffness of joint, not elsewhere classified

ankylosis of joint (M24.6-)
contracture of joint (M24.5-)

Excludes2 inherited from the categories above M25.66

Also inherited, and the opposite of Excludes1: these conditions are not part of M25.66, but a patient can have both, so you may code both.

Written on M25 — Other joint disorder, not elsewhere classified

abnormality of gait and mobility (R26.-)
acquired deformities of limb (M20-M21)
calcification of bursa (M71.4-)
calcification of shoulder (joint) (M75.3)
calcification of tendon (M65.2-)
difficulty in walking (R26.2)
temporomandibular joint disorder (M26.6-)

Risk adjustment

M25.66 does not map to an HCC and does not risk-adjust under CMS-HCC V28. That is normal — most ICD-10 codes do not. It still needs to be coded correctly; it just will not move a RAF score.

Code history

M25.66 has not changed since FY2024 — no addition, revision or deletion across the three most recent ICD-10-CM releases.

Code to one of these instead M25.66

3 child codes. Green means billable.

Related codes at this level

Codes that share M25.6. If M25.66 is not quite right, the correct code is usually one of these.

Questions about M25.66

Is M25.66 a billable ICD-10-CM code?: No. M25.66 is a non-billable header code. Code to a higher level of specificity using one of its child codes.
Where does M25.66 sit in the tabular list?: Diseases of the musculoskeletal system and connective tissue (M00-M99), in the block Other joint disorders (M20-M25).
What cannot be coded together with M25.66?: M25.66 carries Excludes1 notes, which means the conditions they list can never be coded together with it on the same encounter. Some are written on the categories above M25.66 (M25.6) and apply to it just the same.