Is M65 a billable ICD-10-CM code?

No. M65 is a non-billable header code. Code to a higher level of specificity using one of its child codes.

Where does M65 sit in the tabular list?

Diseases of the musculoskeletal system and connective tissue (M00-M99), in the block Disorders of synovium and tendon (M65-M67).

What cannot be coded together with M65?

M65 carries an Excludes1 note, which means the conditions it lists can never be coded together with it on the same encounter.

M65

M65 — Synovitis and tenosynovitis

Non-billable headerICD-10-CM

M65 is a non-billable header ICD-10-CM code for synovitis and tenosynovitis. It cannot be billed on its own: choose one of the more specific child codes below.

Excludes1 — never code together

These conditions cannot occur together. Billing both on the same encounter is a denial.

chronic crepitant synovitis of hand and wrist (M70.0-)
current injury - see injury of ligament or tendon by body region
soft tissue disorders related to use, overuse and pressure (M70.-)

Other codes that can never be billed with M65

These codes carry an Excludes1 note pointing at M65. The conflict binds both ways, but ICD-10-CM only writes it down on one side — so you would not find this by reading M65 alone.

M20.0Deformity of finger(s)
M25.4Effusion of joint
M61.4Other calcification of muscle

Risk adjustment

M65 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 to one of these instead M65

7 child codes. Green means billable.

Questions about M65

Is M65 a billable ICD-10-CM code?: No. M65 is a non-billable header code. Code to a higher level of specificity using one of its child codes.
Where does M65 sit in the tabular list?: Diseases of the musculoskeletal system and connective tissue (M00-M99), in the block Disorders of synovium and tendon (M65-M67).
What cannot be coded together with M65?: M65 carries an Excludes1 note, which means the conditions it lists can never be coded together with it on the same encounter.