INTRODUCTION TO KNEE ARTHROSCOPY

The knee is the premier joint in which arthroscopy has achieved its greatest diagnostic and intraarticular surgical application. Over the past several decades, the usefulness of arthroscopic techniques in the diagnosis and treatment of intraarticular pathology has been exhaustively documented and universally adopted. Today, knee arthroscopy is a foundational skill for the orthopaedic surgeon, serving as the gateway to complex ligamentous reconstructions, meniscal repairs, and cartilage restoration procedures.

However, arthroscopy must be considered a diagnostic aid used in conjunction with a meticulous history, a comprehensive physical examination, and appropriate radiographic imaging. It serves as an adjunct to—not a replacement for—a thorough clinical evaluation. With the exponential increase in the proficiency of extremity examinations and the advent of highly accurate adjuvant tests, particularly high-resolution Magnetic Resonance Imaging (MRI), the era of the purely "diagnostic arthroscopy" has largely passed.

Clinical Pearl: We rarely, if ever, perform a simple “diagnostic arthroscopy.” Surgical alternatives and potential interventions must be thoroughly discussed with the patient prior to the procedure. The definitive surgical procedure should be executed concurrently with the thorough arthroscopic examination.

PREOPERATIVE EVALUATION AND INDICATIONS

The decision to proceed with knee arthroscopy must be rooted in evidence-based indications. The surgeon must correlate the patient's subjective complaints (e.g., mechanical catching, locking, giving way, or localized pain) with objective physical findings (e.g., joint line tenderness, positive McMurray or Lachman tests, and the presence of an effusion).

The Role of Advanced Imaging

While MRI is highly sensitive and specific for meniscal and cruciate ligament pathology, it is not infallible. False positives and false negatives occur, particularly concerning chondral lesions and subtle meniscal root tears. Arthroscopy provides dynamic, magnified, and tactile evaluation of intraarticular structures that static imaging cannot replicate.

Patient Counseling and Consent

Informed consent must encompass the potential for various interventions based on intraoperative findings. The patient must understand that the surgical plan may evolve once the joint is directly visualized. Discussions should include:
* Potential for meniscectomy versus meniscal repair.
* Management of unexpected chondral defects (e.g., chondroplasty, microfracture).
* The possibility of deferring definitive reconstruction (e.g., ACL tear) if pre-operative criteria (such as full range of motion) have not been met.

ANESTHESIA PROTOCOLS

Arthroscopy of the knee can be performed as the essential initial step before proceeding to operative arthroscopy or an open arthrotomy. The choice of anesthesia—local, regional block, or general—depends on the anticipated complexity of the procedure, the patient's physiological status, and the surgeon's preference.

Local Anesthesia

If the procedure is uncomplicated, of short duration, and the patient is highly cooperative, knee arthroscopy can be performed under local anesthesia. This is particularly viable for experienced arthroscopists performing straightforward partial meniscectomies or loose body removals.

Our preferred protocol for local anesthesia includes:
* Intravenous Sedation: Administered by the anesthesia team to ensure patient comfort and anxiolysis.
* Portal Infiltration: Local injection of 1% lidocaine at the planned portal sites.
* Intraarticular Bolus: A mixture of 30 mL of bupivacaine (0.5%) and 15 mL of lidocaine (1% or 2%) injected directly into the joint space 20 minutes before the initiation of the procedure. This delay is critical to allow adequate diffusion and onset of the anesthetic block across the synovial lining.

Regional and General Anesthesia

Diagnostic arthroscopy preceding a major arthrotomy or complex intraarticular surgery (e.g., multiligamentous reconstruction) is generally best performed under general anesthesia or a robust regional block (spinal or epidural), unless contraindicated. General anesthesia provides complete muscle relaxation, which is invaluable for stressing the joint to evaluate ligamentous laxity and for opening the posterior compartments during the arthroscopic sweep.

ASEPSIS AND INFECTION PROPHYLAXIS

The procedure must be performed in the operating room under strict sterile conditions. The minimally invasive nature of arthroscopy often leads to a dangerous underestimation of its surgical gravity. The seriousness of this procedure must not be minimized.

Surgical Warning: Although complications such as intraarticular infection are infrequent (historically < 1%), carelessness in surgical scrubbing, preparation, draping, or the handling of irrigating solutions and instruments can result in septic arthritis. An intraarticular infection following arthroscopy is just as devastating as one following an open arthrotomy, potentially leading to rapid chondrolysis and early osteoarthritis.

Strict Sterile Technique

To minimize the risk of postoperative infection, the following protocols are mandatory:
* Equipment Sterilization: Absolute adherence to sterilization protocols for all arthroscopes, light cables, and motorized instruments.
* Barrier Protection: Mandatory use of waterproof arthroscopy gowns and impervious drapes to prevent strike-through contamination from irrigation fluid.
* Extremity Isolation: Sealing the extremity proximal and distal to the arthroscopy site using impervious stockinettes and cohesive bandages.
* Skin Preparation: Utilization of a durable, alcohol-based skin preparation (e.g., DuraPrep or ChloraPrep) followed by the application of an iodine-impregnated adhesive drape (e.g., Ioban) directly over the surgical site.

OPERATING ROOM SETUP AND ERGONOMICS

Efficiency and safety in knee arthroscopy rely heavily on a standardized operating room setup. Ergonomics play a critical role in minimizing surgeon fatigue and preventing iatrogenic injury to the patient.

Patient Positioning

The patient is positioned supine on the operating table. Two primary methods are utilized for leg control:
1. Circumferential Leg Holder: Placed on the proximal thigh, allowing the distal femur to be rigidly fixed. This acts as a fulcrum to apply valgus or varus stress, opening the medial and lateral compartments, respectively. The end of the table is dropped to allow the knee to flex to 90 degrees or more.
2. Lateral Post: A padded post is fixed to the side of the table at the level of the mid-thigh. The leg rests flat on the table, and the surgeon uses the post as a fulcrum to apply valgus stress. This setup is often preferred for ACL reconstructions as it allows unrestricted manipulation of the extremity.

A well-padded tourniquet is applied to the proximal thigh. While routine inflation is not always necessary due to the tamponade effect of the arthroscopic fluid pump, it should be available and tested prior to draping.

Equipment and Instrumentation Layout

The scrub nurse utilizes a large back table for the primary instrument tray. This table is positioned for the nurse’s convenience, strictly on the same side as the operative knee.
* The Mayo Stand: A Mayo stand is positioned over the operating table at the upper part of the patient’s thighs. The most commonly used instruments (probe, basket forceps, motorized shaver, and graspers) are placed here for immediate access.
* Cables and Tubing: Power cords, light cables, and camera cords are attached to the appropriate consoles and routed off the sterile field to a side table or boom.
* Fluid Management: Irrigation bags are suspended from an intravenous stand at the head of the table (if using gravity) or connected to an automated fluid management pump. Automated pumps maintain a constant intraarticular pressure (typically 40–60 mm Hg), which provides excellent hemostasis and joint distension.

PORTAL PLACEMENT AND ANATOMY

Accurate portal placement is the most critical step in knee arthroscopy. Poorly placed portals lead to instrument crowding, iatrogenic cartilage damage, and an inability to access specific intraarticular zones.

Standard Portals

• Anterolateral Portal: The primary viewing portal. It is established 1 cm above the lateral joint line and 1 cm lateral to the patellar tendon. A vertical or horizontal incision may be used, taking care to incise only the skin to avoid damaging branches of the saphenous nerve.
• Anteromedial Portal: The primary working portal. It is established under direct intraarticular visualization using a spinal needle to ensure the trajectory allows access to the posterior horns of the menisci without damaging the medial femoral condyle. It is typically located 1 cm above the medial joint line and 1 cm medial to the patellar tendon.
• Superolateral Portal: Often used for fluid outflow or for viewing the patellofemoral joint tracking dynamically. It is placed just proximal and lateral to the superior pole of the patella.

Surgical Pitfall: Placing the anterior portals too low (inferior to the joint line) will result in instruments passing through the anterior horn of the meniscus or the infrapatellar fat pad, severely limiting mobility and potentially causing iatrogenic meniscal tears.

THE SYSTEMATIC DIAGNOSTIC EXAMINATION

Once the anterolateral portal is established and the arthroscope is introduced, a rigorous, systematic 14-point examination of the knee must be performed. The surgeon must resist the temptation to immediately address the primary pathology (e.g., a known meniscal tear) before completing the full diagnostic sweep, as secondary pathologies are frequently missed.

1. The Suprapatellar Pouch

The arthroscope is directed superiorly into the suprapatellar pouch. The surgeon evaluates the synovial lining for hypertrophy, erythema, or crystalline deposits. The pouch is a common hiding place for loose bodies, which must be identified and removed.

2. The Patellofemoral Joint

The arthroscope is withdrawn slightly to view the undersurface of the patella and the femoral trochlea.
* Cartilage Evaluation: The articular cartilage is probed for softening (chondromalacia), fissuring, or full-thickness delamination.
* Dynamic Tracking: The knee is taken through a range of motion from extension to flexion to observe patellar tracking and identify any lateral subluxation or tilt.

3. The Medial Gutter

The arthroscope is swept down the medial side of the knee into the medial gutter. The surgeon looks for medial synovial plicae, which can become thickened and fibrotic, causing mechanical impingement against the medial femoral condyle.

4. The Medial Compartment

The knee is flexed to 10–30 degrees, and a valgus stress is applied against the leg holder or lateral post to open the medial compartment. The anteromedial portal is established, and a tactile probe is introduced.
* Medial Meniscus: The meniscus is probed systematically from the posterior root, through the posterior horn, body, and anterior horn. The surgeon must probe the inferior surface, as hidden cleavage tears often reside here.
* Articular Cartilage: The weight-bearing surfaces of the medial femoral condyle and medial tibial plateau are evaluated for chondral defects.

5. The Intercondylar Notch

The knee is flexed to 90 degrees, and the arthroscope is directed into the intercondylar notch.
* Anterior Cruciate Ligament (ACL): The ACL is visualized and probed to assess its tension, synovial coverage, and structural integrity. A "pseudo-intact" ACL may appear continuous but lack tension when probed.
* Posterior Cruciate Ligament (PCL): The PCL is visualized behind the ACL. Its robust, synovial-covered fibers should be inspected.
* Notch Anatomy: The presence of osteophytes narrowing the notch (notch stenosis) should be noted, as this can impinge on the ACL.

6. The Lateral Compartment

The knee is placed in a "figure-of-four" position (flexed, abducted, and externally rotated) while applying a varus stress to open the lateral compartment.
* Lateral Meniscus: The lateral meniscus is probed. Special attention is given to the popliteus hiatus, a normal anatomic gap where the popliteus tendon passes. The surgeon must differentiate between a normal hiatus and a peripheral meniscal tear.
* Articular Cartilage: The lateral femoral condyle and lateral tibial plateau are inspected.

7. The Lateral Gutter

Finally, the arthroscope is directed into the lateral gutter to inspect for loose bodies and evaluate the popliteus tendon as it courses proximally to its femoral insertion.

POSTOPERATIVE PROTOCOLS AND REHABILITATION

Following the completion of the diagnostic sweep and any subsequent operative interventions, the joint is thoroughly irrigated to remove all debris, cartilage fragments, and blood clots.

Closure and Dressing

• The portals are closed using non-absorbable sutures (e.g., 3-0 nylon) or adhesive skin tapes, depending on surgeon preference and portal size.
• A sterile, bulky compressive dressing is applied from the mid-calf to the mid-thigh to minimize postoperative hemarthrosis and swelling.

Immediate Postoperative Care

• Weight-Bearing: If only a diagnostic arthroscopy, partial meniscectomy, or chondroplasty was performed, patients are generally allowed to weight-bear as tolerated immediately postoperatively. If a meniscal repair or microfracture was performed, strict weight-bearing restrictions and range-of-motion limitations are instituted.
• Cryotherapy: Continuous cold therapy is highly recommended to reduce pain and effusion.
• Rehabilitation: Early physical therapy is initiated to restore full extension, improve quadriceps activation, and normalize gait.

Mastery of these basic diagnostic techniques, strict adherence to asepsis, and a profound understanding of operating room ergonomics form the bedrock of successful knee arthroscopy. Only through the disciplined execution of these foundational principles can the orthopaedic surgeon safely and effectively manage complex intraarticular pathology.