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    OpenPayerBilling CodesExcision Procedures on the Femur (Thigh Region) and Knee JointCPT cpt-27331-knee-arthrotomy-biopsy-loose-body-removal
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    CPT 27331: Knee Arthrotomy with Synovial Biopsy and Loose Body Removal

    Medicare pays $470 on average nationally for this procedure.

    CPT code 27331 describes a surgical arthrotomy of the knee involving incision into the joint with biopsy and removal of a loose body from the synovium, a surgical service typically performed in an operating room or ambulatory surgical center under appropriate anesthesia; this code represents the operative procedure and associated intraoperative diagnostic tissue sampling for patients presenting with intra-articular loose bodies or synovial lesions.

    For related coverage guidance, see recent payer policy updates: Removal of Implantable, Outpatient Surgical Procedures - Site of Service, Surgical Procedures.

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    Table of contents

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    Clinical & Coding Specifications

    Clinical Context

    A 45-year-old patient presents with persistent knee pain, swelling, mechanical locking, and episodes of catching after a twisting injury sustained while playing recreational soccer. Physical exam demonstrates joint line tenderness and limited range of motion. Preoperative knee radiographs show a possible loose intra-articular fragment; MRI confirms a synovial loose body and synovial irritation. The orthopedic surgeon schedules an open arthrotomy of the knee to obtain a synovial biopsy and remove the loose body when arthroscopic removal is contraindicated due to fragment size, location, or prior surgical anatomy.

    The clinical workflow includes preoperative evaluation and imaging, informed consent discussing risks and alternatives, operative arthrotomy with synovial biopsy and extraction of the loose body, intraoperative specimen labeling and submission to pathology, postoperative pain control, wound care, and brief inpatient observation or same-day discharge depending on the patient’s status and anesthetic. Documentation must record indications, findings, size/number of loose bodies, biopsy site, specimens submitted, estimated blood loss, implants if any, and the applicable operative and anesthesia details for accurate coding and billing.

    Related CPT Codes

    CPT CodeDescriptionRelationship to This Procedure
    27331Arthrotomy, knee, with biopsy and removal of loose body from synoviumThis is the primary procedure code describing open knee arthrotomy with synovial biopsy and loose body removal.
    23700Arthrotomy, elbow; with exploration, drainage, or extirpationAnalogue for open joint procedures at a different anatomic site; not performed with 27331 but similar technique.
    29881Arthroscopy, knee, surgical; synovectomy, limitedArthroscopic alternative to open arthrotomy for synovial biopsy and loose body removal when feasible.
    29874Arthroscopy, knee, surgical; debridement/shaving of articular cartilage (chondroplasty)Commonly performed arthroscopically alongside loose body removal when cartilage damage is present.
    28070Excision, tumor, soft tissue of knee area, deepMay be used when a larger synovial or soft tissue mass is excised during open procedure.
    88305Pathology examination, gross and microscopic, surgical pathology, single specimenUsed for billing the synovial biopsy and loose body histopathology evaluation; reported by pathology service.

    Related Modifiers

    11 rows

    ModifierDescriptionWhen to Use
    26Modifier 26 (Professional Component) identifies and bills only the professional portion of a split service — the physician’s interpretation, report, and medical judgment — when the technical…- Use CPT Modifier -26 when you are billing only the professional component (PC) of a split‑bill eligible service—i.e., you performed the physician interpretation, medical judgment and prepared a…
    50Modifier –50 (Bilateral Procedure) is appended to a CPT code when an identical procedure is performed on paired anatomical structures during the same operative session. The AMA states to add…- Use modifier -50 when the same CPT surgical, diagnostic, or radiology procedure is performed on paired anatomical structures (both sides of the body) during the same operative/session by the same…
    51Modifier –51 (Multiple Procedures) is used when the same provider performs multiple procedures in the same session to identify secondary, non‑exempt procedures and indicate payment reduction logic…- Use modifier -51 when the same provider performs multiple distinct procedures during the same patient encounter: report the highest‑valued procedure first (no modifier) and append -51 to…
    52Modifier ‑52 (Reduced Services) indicates that a service or procedure was partially reduced or omitted at the provider’s discretion, allowing reporting of the basic procedure number with a qualifier…- Use modifier -52 when a physician or qualified health professional electively reduces or omits part of a procedure or service (for example, performing fewer required views or omitting a portion of…
    53Modifier 53 (Discontinued Procedure) signals that a surgical or diagnostic service was begun by the physician but terminated because of extenuating circumstances that threatened the patient’s…- Use modifier -53 when a physician/qualified healthcare professional has started a surgical or diagnostic procedure (e.g., anesthesia administered, incision or scope insertion) and then discontinues…
    59Modifier 59 indicates a distinct procedural service when two procedures that are not normally billed together are clinically and procedurally separate. The CPT definition (as reiterated by CMS)…- Use modifier -59 to report a distinct procedural service when documentation supports that the procedure reported is not normally billed together with another service on the same day because of a…
    62Modifier 62 indicates that two surgeons function as co‑surgeons, each performing distinct parts of the same primary surgical procedure. It is appended to the primary procedure code (and any…- Use modifier -62 when two surgeons act as co‑surgeons (both primary surgeons) on a single definitive primary procedure, each performing distinct parts of the same surgical procedure (append -62 to…
    78CPT modifier -78 indicates an unplanned, related return to the operating or procedure room by the same provider during the global postoperative period. It is appended when treatment for a…- Use modifier -78 when an unplanned, related complication during the original procedure’s global postoperative period requires the patient to return to a formal operating or procedure room and the…
    79Modifier 79 indicates a surgical procedure performed during the postoperative global period of a prior surgery that is unrelated to the original procedure. Per AMA/CPT and CMS guidance, it is…- Use modifier 79 when the same physician (or same‑specialty physician in the same group) performs a surgical procedure during the postoperative global period of a prior surgery and the new procedure…
    76Modifier -76, Repeat Procedure or Service by Same Physician or Other Qualified Health Care Professional, is appended when the same provider performs an identical, medically necessary procedure or…- Use modifier -76 when the same physician or other qualified health care professional performs an identical procedure or service a second (or subsequent) time on the same date of service and the…

    Showing 1–10 of 11

    Related Provider Taxonomies

    8 rows

    Taxonomy Code
    207K00000X
    207L00000X
    261QR0400X
    261QF0050X
    3416A0800X
    2080P0203X
    293D00000X
    2251E1200X

    Related ICD-10-CM Codes

    21 rows

    ICD-10-CM CodeDescription
    M00.261Other streptococcal arthritis, right knee
    M00.269Other streptococcal arthritis, unspecified knee
    M05.869Other rheumatoid arthritis with rheumatoid factor of unspecified knee
    M06.069Rheumatoid arthritis without rheumatoid factor, unspecified knee
    M12.569Traumatic arthropathy, unspecified knee
    M17.0Bilateral primary osteoarthritis of knee
    M17.11Unilateral primary osteoarthritis, right knee
    M17.12Unilateral primary osteoarthritis, left knee
    M17.9Osteoarthritis of knee, unspecified
    M25.261Flail joint, right knee

    Showing 1–10 of 21

    Related Payer Policy Updates

    Specialty: General Surgery1 / 3

    10 rows

    PolicyPayerEffective Date
    Removal of ImplantableBlue Cross Blue Shield - Rhode Island2026-10-01
    Outpatient Surgical Procedures - Site of ServiceUnitedHealthcare2026-09-01
    Surgical ProceduresUnitedHealthcare2026-09-01
    Site of Service Ambulatory Service Center (ASC) Select — Surgical or Diagnostic Procedures in AdultsPremera Bluecross2026-09-01
    Site of Service Ambulatory Surgical Center (ASC) Select — Surgical or Diagnostic Procedures in AdultsPremera Bluecross2026-09-01
    Site of Service Ambulatory Service Center (ASC) SelectPremera Bluecross2026-09-01
    Site of Service Ambulatory Surgical Center (ASC) Select — Site of Service for Ambulatory Surgical Procedures (ASC Select)Premera Bluecross2026-09-01
    Site of Service Ambulatory Service Center (ASC) SelectPremera Bluecross2026-09-01
    Medical Necessity Guidelines Inpatient Surgical CareMass General Brigham Health Plan2026-08-01
    Outpatient Surgical Procedures - Site of Servicesierra health and life2026-08-01

    Related Codes

    CPT-27323-EXCISIONAL-BIOPSY-THIGH-KNEE-SUPERFICIAL-SOFT-TISSUE

    CPT 27323: Excisional Biopsy of Superficial Soft Tissue, Thigh or Knee

    CPT-27324-DEEP-SOFT-TISSUE-BIOPSY-THIGH-KNEE

    CPT 27324: Deep Tissue/Muscle Biopsy of Thigh or Knee

    CPT-27325-HAMSTRING-NEURECTOMY-NERVE-EXCISION

    CPT 27325: Neurectomy of Nerve Along Hamstring

    CPT-27326-POPLITEAL-GASTROCNEMIUS-NERVE-EXCISION-FOR-SPASM

    CPT 27326: Neurectomy of Popliteal/Gastrocnemius Nerve for Spasm

    CPT-27327-SUBCUTANEOUS-TUMOR-EXCISION-THIGH-KNEE

    CPT 27327: Excision of Subcutaneous Tumor of Thigh or Knee (<3 cm)

    CPT-27328-INTRAMUSCULAR-THIGH-KNEE-TUMOR-EXCISION-SMALL

    CPT 27328: Excision of Intramuscular Tumor of Thigh or Knee (<5 cm)

    CPT-27329-EXTENSIVE-EXCISION-SOFT-TISSUE-TUMOR-THIGH-KNEE-LESS-5CM

    CPT 27329: Extensive Excision of Soft-Tissue Tumor, Thigh/Knee (<5 cm)

    CPT-27330-KNEE-SYNOVIAL-BIOPSY-SURGICAL-DIAGNOSTIC

    CPT 27330: Open Biopsy of Synovium of Knee

    CPT-27332-KNEE-ARTHROTOMY-MENISCAL-EXCISION

    CPT 27332: Arthrotomy with Excision of Medial or Lateral Meniscus

    CPT-27333-KNEE-PARTIAL-MENISCECTOMY-MEDIAL-AND-LATERAL

    CPT 27333: Meniscectomy, Medial and Lateral Knee

    Showing 1–10 of 25

    Frequently Asked Questions

    References

    1. 1.CPT® Codes and Descriptions. AAPC. Retrieved Aug 11, 2026.Maintains the CPT code set's official descriptions and guidelines, licensed from the American Medical Association, used as the definitional source for CPT codes on this page.
    2. 2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's quarterly release of HCPCS Level II codes and short/long descriptors, the source for HCPCS code definitions and update history.
    3. 3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's complete ICD-10-CM diagnosis code list, used to cross-reference diagnosis codes associated with this procedure or service.
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