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.