29870

Arthroscopy, knee, diagnostic, with or without synovial biopsy (separate procedure)

CPT code 29870 describes a diagnostic arthroscopy of the knee joint. This minimally invasive procedure involves the insertion of an arthroscope (a small camera) through tiny incisions (portals) into the knee joint to visualize its internal structures, including the menisci, articular cartilage, ligaments, and synovium. It is typically performed when non-invasive diagnostic studies (e.g., MRI, X-rays) are inconclusive or contradictory, or to confirm findings before definitive surgical intervention. The procedure allows for direct inspection of joint pathology, assessment of the extent of disease, and identification of mechanical derangements. A synovial biopsy may be performed during the diagnostic arthroscopy if indicated for further pathological examination (e.g., suspected inflammatory arthritis, infection, or tumor), and its performance is included in this code.

Clinical Indications

  • Persistent, unexplained knee pain, swelling, or mechanical symptoms (e.g., locking, clicking, catching) after failure of conservative management and inconclusive non-invasive imaging studies.
  • Evaluation of internal derangement of the knee (e.g., meniscal tears, ligamentous injuries, chondral defects) where imaging findings are equivocal or do not correlate with clinical symptoms.
  • Assessment of the extent of articular cartilage damage or osteoarthritis, particularly when considering surgical treatment options.
  • Diagnosis of inflammatory arthropathies, synovial disorders (e.g., pigmented villonodular synovitis, chronic synovitis), or suspected intra-articular infection requiring synovial tissue for biopsy and culture.
  • Investigation and localization of suspected intra-articular loose bodies that are not clearly identified or localized by imaging.
  • Confirmation of pre-operative diagnoses prior to planned therapeutic arthroscopic or open knee surgery.

Procedure Steps

  1. Patient positioned supine on the operating table, often with a tourniquet applied to the thigh and the knee flexed.
  2. Administration of appropriate anesthesia (e.g., regional, general, or local with sedation).
  3. Sterile preparation and draping of the operative knee.
  4. Creation of standard arthroscopic portals (typically anteromedial and anterolateral) after local anesthetic infiltration.
  5. Introduction of the arthroscope into the joint, followed by establishment of continuous fluid inflow and outflow.
  6. Systematic visualization and examination of all compartments of the knee: patellofemoral, medial tibiofemoral, lateral tibiofemoral, and the intercondylar notch.
  7. Identification and documentation of any abnormalities, including meniscal tears, chondral lesions, ligamentous integrity, synovial changes, and presence of loose bodies.
  8. If indicated, performance of a synovial biopsy using grasping forceps or a biopsy punch inserted through a portal.
  9. Removal of the arthroscope and instruments.
  10. Closure of portal incisions with sutures, steri-strips, or adhesive strips.
  11. Application of sterile dressing and a compression bandage to the knee.

Coding Guidelines

  • CPT code 29870 is designated as a 'separate procedure.' This means it should not be reported separately when performed in conjunction with a more extensive therapeutic arthroscopic procedure on the same knee during the same operative session. The diagnostic component is considered an inherent part of the therapeutic procedure.
  • If a diagnostic arthroscopy is performed and subsequently a therapeutic arthroscopic procedure (e.g., meniscectomy, chondroplasty, synovectomy) is carried out through the same arthroscopic incisions, only the therapeutic code should be reported.
  • This code includes 'with or without synovial biopsy.' Therefore, a synovial biopsy performed during a diagnostic arthroscopy of the knee should not be billed separately.
  • Modifier -RT (right) or -LT (left) should be appended to indicate laterality of the knee being scoped. If performed bilaterally, modifier -50 (bilateral procedure) should be appended to 29870.
  • If a diagnostic arthroscopy is performed and, due to findings, the therapeutic procedure is aborted or performed as an open procedure, 29870 may be reported along with modifier -52 (reduced services) if appropriate, or the relevant open procedure code.
  • A 0-day or 10-day global period typically applies to this procedure, depending on the payer and specific circumstances.

Associated ICD-10 Codes