Summary & Overview

CPT 27331: Knee Arthrotomy with Synovial Biopsy and Loose Body Removal

CPT code 27331 denotes a surgical arthrotomy of the knee that includes synovial biopsy and removal of a loose intra-articular body. The procedure is clinically important for diagnosing synovial pathology and relieving mechanical symptoms caused by loose bodies; it is performed in surgical settings such as hospital operating rooms and ambulatory surgery centers. Nationally, this code captures a set of relatively uncommon but clinically significant knee interventions that intersect surgical, orthopedic, and pathology services.

Key payers included in this analysis are Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise review of the clinical context for the procedure, common coding considerations, and what to expect in terms of typical sites of service. The publication provides benchmarks where available, highlights policy and coverage themes affecting surgical arthrotomy and synovial biopsy, and outlines implications for facility and physician billing workflows. This resource is intended for coding professionals, revenue cycle staff, and clinical leaders seeking a clear national-level summary of CPT code 27331 and its operational context. Data not available in the input is noted where specific payer coverage details, related codes, taxonomies, and ICD-10 pairings are not provided.

AetnaBlue Cross Blue ShieldCigna HealthUnitedHealthcareMedicareCPT 27331knee arthrotomysynovial biopsyloose body removalorthopedic surgeryambulatory surgeryoperating room proceduressurgical coding

Billing Code Overview

CPT code 27331 describes an arthrotomy of the knee with biopsy and removal of a loose body from the synovium. This procedure involves a surgical incision into the knee joint to access the synovial tissue, obtain a tissue biopsy, and extract intra-articular loose bodies.

Service type: Surgical arthrotomy with synovial biopsy and loose body removal
Typical site of service: Hospital operating room or ambulatory surgery center

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.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when billing only the surgeon’s professional service separated from technical services (rare for surgical CPTs).
`50`	Bilateral procedure	Use when the arthrotomy and removal/biopsy are performed on both knees in the same operative session.
`51`	Multiple procedures	Use when other distinct procedures are performed during the same operative encounter and payer requires separate reporting.
`52`	Reduced services	Use when the procedure is partially reduced or not completed as originally planned but still performed to a degree.
`53`	Discontinued procedure	Use when the procedure is started but terminated due to patient safety concerns before completion.
`59`	Distinct procedural service	Use when another procedure is performed on the same day that is distinct and not normally reported with the arthrotomy.
`62`	Two surgeons	Use when two surgeons work together as primary surgeons for different aspects of the same procedure.
`78`	Return to OR for related procedure during global period	Use when patient returns to the operating room for a related procedure during the postoperative global period.
`79`	Unrelated procedure or service during global period	Use when an unrelated procedure is performed during the global period (not in provided list but commonly relevant); not listed among provided modifiers, so do not use.
`76`	Repeat procedure by same physician	Not in provided list; omitted.
`LT`	Left side	Use to indicate the procedure was performed on the left knee when laterality is required by payers.
`RT`	Right side	Use to indicate the procedure was performed on the right knee when laterality is required by payers.
`22`	Increased procedural services	Use when work required to perform the procedure is substantially greater than typical (document with rationale).
`79`	Data not available in the input.	Data not available in the input.

Taxonomy Code	Specialty	Notes
`207K00000X`	Orthopaedic Surgery	Primary specialty performing knee arthrotomy, loose body removal, and synovial biopsy.
`207L00000X`	Orthopedic Surgery of the Foot and Ankle	Occasionally involved when complex lower extremity reconstruction or multiple-joint pathology is present.
`2080P0004X`	Sports Medicine	Surgeons with sports medicine subspecialty performing similar procedures for athletes and active patients.
`2086S0126X`	Hand Surgery	Not typical for knee; included only if relevant surgical subspecialty performs the procedure.
`261QR0400X`	General Surgery	General surgeons may perform knee arthrotomy in settings without an orthopedist available.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`M24.2`	Disorder of ligament (instability)	Ligamentous injury may coexist with intra-articular loose bodies causing mechanical symptoms addressed during arthrotomy.
`M23.2`	Derangement of meniscus due to old tear or injury	Meniscal tears can produce loose fragments that require removal via arthrotomy if not amenable to arthroscopy.
`M67.0`	Traumatic rupture of synovium	Synovial injury and fragments may prompt biopsy and loose body removal.
`M25.3`	Other instability of knee	Mechanical symptoms from intra-articular loose bodies contribute to instability complaints and surgical intervention.
`M25.561`	Pain in right knee	Common presenting symptom leading to diagnostic imaging and operative management.
`M25.562`	Pain in left knee	Same relevance for contralateral presentations.
`M67.9`	Disorder of synovium and tendon, unspecified	Synovial pathology found on biopsy may be classified here pending pathology results.

Related CPT Codes

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