ICD-10-CM 2027
ICD-10 code for synovitis
From the official ICD-10-CM alphabetic index entry “Synovitis”. Page updated September 29, 2026.
About coding synovitis
The ICD-10-CM code for synovitis is M65.90 (Unspecified synovitis and tenosynovitis, unspecified site). The official index lists 42 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on M65.90.
Within M65.9, choose M65.90 (unspecified site) only when documentation doesn't support a more specific option: shoulder (M65.91), upper arm (M65.92), forearm (M65.93), hand (M65.94), thigh (M65.95), lower leg (M65.96), ankle and foot (M65.97), other site (M65.98) and 1 more.
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 557 (Tendonitis, Myositis and Bursitis with MCC, relative weight 1.489) and DRG 558 (Tendonitis, Myositis and Bursitis without MCC, relative weight 0.8875), 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.
More specific synovitis codes (official index)
- ankle and foot M65.97 — Unspecified synovitis and tenosynovitis, ankle and foot
- arm, upper M65.92 — Unspecified synovitis and tenosynovitis, upper arm
- crepitant
- hand M70.04 — Crepitant synovitis (acute) (chronic), hand
- wrist M70.03 — Crepitant synovitis (acute) (chronic), wrist
- forearm M65.93 — Unspecified synovitis and tenosynovitis, forearm
- gonococcal A54.49 — Gonococcal infection of other musculoskeletal tissue
- gouty
- hand M65.94 — Unspecified synovitis and tenosynovitis, hand
- in (due to)
- crystals M65.8 — Other synovitis and tenosynovitis
- gonorrhea A54.49 — Gonococcal infection of other musculoskeletal tissue
- syphilis (late) A52.78 — Syphilis of other musculoskeletal tissue
- use, overuse, pressure
- infective NEC
- leg, lower M65.96 — Unspecified synovitis and tenosynovitis, lower leg
- multiple sites, unspecified type M65.99 — Unspecified synovitis and tenosynovitis, multiple sites
- shoulder M65.91 — Unspecified synovitis and tenosynovitis, shoulder
- specified NEC
- specified site, unspecified type M65.98 — Unspecified synovitis and tenosynovitis, other site
- syphilitic A52.78 — Syphilis of other musculoskeletal tissue
- congenital (early) A50.02 — Early congenital syphilitic osteochondropathy
- thigh M65.95 — Unspecified synovitis and tenosynovitis, thigh
- toxic
- transient M67.3 — Transient synovitis
- ankle M67.37 — Transient synovitis, ankle and foot
- elbow M67.32 — Transient synovitis, elbow
- foot joint M67.37 — Transient synovitis, ankle and foot
- hand joint M67.34 — Transient synovitis, hand
- hip M67.35 — Transient synovitis, hip
- knee M67.36 — Transient synovitis, knee
- multiple site M67.39 — Transient synovitis, multiple sites
- pelvic region M67.35 — Transient synovitis, hip
- shoulder M67.31 — Transient synovitis, shoulder
- specified joint NEC M67.38 — Transient synovitis, other site
- wrist M67.33 — Transient synovitis, wrist
- traumatic, current
- tuberculous
- villonodular (pigmented) M12.2 — Villonodular synovitis (pigmented)
- ankle M12.27 — Villonodular synovitis (pigmented), ankle and foot
- elbow M12.22 — Villonodular synovitis (pigmented), elbow
- foot joint M12.27 — Villonodular synovitis (pigmented), ankle and foot
- hand joint M12.24 — Villonodular synovitis (pigmented), hand
- hip M12.25 — Villonodular synovitis (pigmented), hip
- knee M12.26 — Villonodular synovitis (pigmented), knee
- multiple site M12.29 — Villonodular synovitis (pigmented), multiple sites
- pelvic region M12.25 — Villonodular synovitis (pigmented), hip
- shoulder M12.21 — Villonodular synovitis (pigmented), shoulder
- specified joint NEC M12.28 — Villonodular synovitis (pigmented), other specified site
- vertebrae M12.28 — Villonodular synovitis (pigmented), other specified site
- wrist M12.23 — Villonodular synovitis (pigmented), wrist
Common questions about synovitis ICD-10 codes
What is the ICD-10 code for synovitis?
- M65.90 — Unspecified synovitis and tenosynovitis, unspecified site. More specific codes apply when the documentation supports them: M65.97, M65.92, M70.04, M70.03 and others below.
What is the ICD-10 code for ankle and foot synovitis?
- M65.97 — Unspecified synovitis and tenosynovitis, ankle and foot (header code; choose a more specific subcode).
What is the ICD-10 code for forearm synovitis?
- M65.93 — Unspecified synovitis and tenosynovitis, forearm (header code; choose a more specific subcode).
What is the ICD-10 code for gonococcal synovitis?
- A54.49 — Gonococcal infection of other musculoskeletal tissue.
What is the ICD-10 code for hand synovitis?
- M65.94 — Unspecified synovitis and tenosynovitis, hand (header code; choose a more specific subcode).
What is the ICD-10 code for shoulder synovitis?
- M65.91 — Unspecified synovitis and tenosynovitis, shoulder (header code; choose a more specific subcode).
What is the ICD-10 code for syphilitic synovitis?
- A52.78 — Syphilis of other musculoskeletal tissue.
Is M65.90 billable?
- Yes. M65.90 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can M65.90 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict M65.90 as a principal diagnosis.
Is M65.90 a CC or MCC?
- No. M65.90 is neither a CC nor an MCC under MS-DRG v44.0.