High Yield Overview

KNEE ARTHROSCOPY APPROACH

Portal Placement | Minimally Invasive | Diagnostic and Therapeutic

Critical Knee Arthroscopy Exam Points

Portal Order

Always AL portal FIRST. This is the viewing portal. Create it blind (but safely with spinal needle first). The AM portal is then created UNDER DIRECT VISION through the arthroscope. Never create AM portal blind.

IPBSN at Risk

The infrapatellar branch of saphenous nerve runs transversely across the anterior knee, typically 3-5mm below the joint line. It is commonly injured during portal placement, causing anterolateral knee numbness. This is similar to open surgery.

Joint Line Level

Portals must be at joint line level. Too proximal risks patellar surface damage; too distal risks meniscus or fat pad injury. Palpate the soft spot adjacent to the patellar tendon with the knee flexed 90 degrees.

Popliteal Structures

Posterior portals risk neurovascular injury. The popliteal artery and tibial nerve are within 5mm of the posterior capsule. Use transillumination and accessory posterior portals only when essential.

At a Glance

Knee arthroscopy uses a standard two-portal technique with the anterolateral (AL) portal for viewing and anteromedial (AM) portal for working instruments. The AL portal is placed 1cm lateral to the patellar tendon at joint line level and is established first; the AM portal is then created under direct visualization 1cm medial to the patellar tendon. The infrapatellar branch of the saphenous nerve (IPBSN) runs transversely 3-5mm below the joint line and is commonly injured, causing anterolateral knee numbness. Portals must be at joint line level—too proximal damages the patella, too distal injures the meniscus or fat pad. Triangulation (working through AM while viewing through AL) is the fundamental skill. Posterior portals risk popliteal neurovascular structures and should only be used when essential.

Mnemonic

PORTALSPORTALS - Standard Knee Arthroscopy Portals

Memory Hook:PORTALS reminds you of the systematic approach to knee arthroscopy portal creation

Mnemonic

SAFETYSAFETY - Structures at Risk

Memory Hook:SAFETY reminds you of what can go wrong in knee arthroscopy

Overview and Indications

Knee arthroscopy is one of the most commonly performed orthopedic procedures worldwide. It allows minimally invasive diagnostic and therapeutic access to all knee compartments.

Primary indications:

Meniscal pathology (tears - repair or partial meniscectomy)
ACL/PCL reconstruction
Cartilage procedures (microfracture, debridement, OATS)
Loose body removal
Synovectomy (inflammatory arthritis, PVNS)
Lateral release for patellofemoral disorders
Diagnostic arthroscopy (when imaging inconclusive)

Evidence for Arthroscopy

Recent evidence (FIDELITY trial, MOSAIC trial) has questioned the role of arthroscopic partial meniscectomy in degenerative meniscal tears. For Exam, know that APM is NOT superior to sham surgery for degenerative tears but remains indicated for mechanical symptoms from acute traumatic tears and for meniscal repair in young patients.

Advantages:

Minimally invasive with small incisions
Direct visualization of intra-articular structures
Same-day surgery in most cases
Rapid rehabilitation compared to open procedures
Can combine diagnostic and therapeutic in single procedure

Disadvantages:

Requires specialized equipment and training
Fluid extravasation and compartment syndrome risk
Limited access to some structures without additional portals
Learning curve for complex procedures

Relevant Anatomy

Surface anatomy for portal placement:

Patella - Superior pole, inferior pole, medial and lateral borders
Patellar tendon - From inferior patella to tibial tubercle
Joint line - Palpable as soft spot adjacent to patellar tendon with knee at 90 degrees
Tibial tubercle - 2-3cm below joint line

Portal positions (standard two-portal technique):

Portal	Position	Purpose
Anterolateral (AL)	1cm lateral to patellar tendon, at joint line	Viewing portal
Anteromedial (AM)	1cm medial to patellar tendon, at joint line	Working portal
Superolateral	2cm above joint line, lateral	Outflow, visualization of patella
Superomedial	2cm above joint line, medial	Rarely used - quadriceps in the way
Posteromedial	Posterior to MCL, at joint line	Posterior horn access, PCL surgery
Posterolateral	Posterior to LCL, at joint line	Popliteus access, posterolateral corner

Structures at risk:

Neurovascular Structures at Risk by Portal

Posterior Portal Safety

The popliteal artery lies within 5-15mm of the posterior capsule. When creating posterior portals: (1) Always use transillumination from the anterior scope, (2) Insert spinal needle under direct vision, (3) Make only skin incision with blade then use blunt trocar, (4) Stay in the plane superficial to the capsule until visualized arthroscopically.

Intra-articular anatomy (systematic examination):

Suprapatellar pouch - Synovium, quadriceps tendon
Medial gutter - Medial synovium, medial femoral condyle
Patellofemoral joint - Articular surfaces, tracking
Medial compartment - MFC, medial tibial plateau, medial meniscus
Intercondylar notch - ACL, PCL insertions
Lateral compartment - LFC, lateral tibial plateau, lateral meniscus
Lateral gutter - Lateral synovium, popliteus hiatus

Preoperative Planning

Assessment:

Detailed history: mechanism, symptoms, mechanical vs inflammatory
Physical examination: effusion, ROM, ligament stability, meniscal tests
Document baseline neurovascular status
Identify contraindications (infection, DVT, compartment syndrome)

Imaging review:

X-rays: Weight-bearing AP, lateral, Rosenberg (45 degree PA flexion), Merchant/skyline
MRI: Standard for most knee arthroscopy indications - meniscus, ACL, cartilage
CT: Rarely needed unless bony pathology or complex fracture

Consent points:

Numbness from infrapatellar nerve injury (10-30% incidence)
Infection (less than 1%)
DVT/PE (rare but serious)
Stiffness or arthrofibrosis
Failure to resolve symptoms (especially degenerative tears)
Progression of arthritis (natural history, not caused by surgery)
Conversion to open procedure (rare)
Specific risks based on planned procedure (meniscal repair failure, etc.)

Equipment Check

Essential equipment: Arthroscope (4mm, 30-degree), light source, camera, pump/gravity inflow, hand instruments (probes, shavers, graspers, cutters), tourniquet (optional).

Tourniquet Decision

Tourniquet use is surgeon-dependent. Benefits: bloodless field, faster surgery. Risks: tourniquet pain, potential nerve compression. Many surgeons use tourniquet only if bleeding obscures vision.

Internervous Plane

Key Concept: There is NO true internervous plane in knee arthroscopy portals.

Unlike open surgical approaches that exploit intervals between muscles supplied by different nerves, arthroscopy uses small stab incisions through skin and capsule. The concept of "internervous plane" is not applicable to portal-based approaches.

Exam Clarification - Portals vs Approaches

Traditional Internervous Plane

Definition: A surgical plane between muscles supplied by different nerves, allowing separation without denervation.

Applies to: Open surgical approaches (medial parapatellar, posterior hip approach, etc.)

Arthroscopic Portals

No internervous plane: Portals are small stab incisions (5-10mm) through skin and capsule directly into the joint.

Key principle: Minimize tissue trauma by staying at joint line, using spinal needle localization, and avoiding major neurovascular structures.

Nerve considerations for portal placement:

The infrapatellar branch of saphenous nerve (IPBSN) is the main nerve at risk. It emerges from beneath the sartorius muscle and runs horizontally across the anterior knee, typically passing 3-5mm below the standard portal sites.

Injury rate: 10-30% in various studies
Consequence: Anterolateral or anteromedial knee numbness
Prevention: Horizontal skin incisions (parallel to IPBSN), staying at joint line level, not overtight sutures

Viva Answer

When asked about internervous planes in knee arthroscopy, state: "The concept of internervous plane is not applicable to arthroscopic portals. These are small stab incisions directly through skin and capsule. The main nerve at risk is the infrapatellar branch of the saphenous nerve, which runs horizontally across the anterior knee. This is avoided by staying at joint line level and using horizontal skin incisions. Injury causes anterolateral numbness but typically resolves or is well-tolerated."

Positioning and Patient Setup

Standard Patient Position:

Supine on operating table
Leg hanging free off the side of the table, or
Leg holder device maintaining 70-90 degrees flexion
Thigh tourniquet if planned (inflated to 300mmHg after exsanguination)
Lateral post at thigh level for valgus stress (medial compartment access)
Foot rest or padded support

Key Setup Considerations:

Knee Position:
- Flexed 70-90 degrees for most work (suprapatellar, anterior compartments)
- Near full extension for posterior horn visualization
- Figure-of-4 position (hip flexion, external rotation) for lateral meniscus
Access Requirements:
- Must be able to apply valgus stress (medial compartment exposure)
- Must be able to apply varus stress (lateral compartment exposure)
- Full flexion and extension must be possible
Draping:
- Free drape the entire lower extremity
- Include thigh in field for tourniquet
- Impermeable drape to contain fluid

Leg Hanging Position

Advantages: Gravity assists flexion, easy to apply varus/valgus stress, simple setup.

Disadvantages: Surgeon must stabilize leg, may be awkward for prolonged cases.

Leg Holder Device

Advantages: Hands-free stabilization, consistent positioning, easier for long cases.

Disadvantages: Cost, setup time, may limit positioning options for some procedures.

Positioning for Specific Procedures:

Meniscal repair: Leg hanging with ability to flex deeply (90-120 degrees)
ACL reconstruction: Leg holder often preferred for consistent positioning during graft passage
Posterior horn work: Near-extension increases posterior visualization
Loose body removal: May need multiple position changes to access all compartments

Surgical Technique

Standard Two-Portal Technique

Step 1: Joint Distension (optional)

Insert spinal needle superolaterally into suprapatellar pouch
Inject 30-60mL saline to distend joint
Alternatively, distend after AL portal with pump

Step 2: Anterolateral Portal (Viewing)

AL Portal Steps

Step 1Landmark

Palpate the soft spot 1cm lateral to the patellar tendon at the level of the inferior pole of the patella. The knee should be flexed 70-90 degrees.

Step 2Spinal Needle Localization

Insert 18g spinal needle through the soft spot, aiming for the intercondylar notch. Confirm intra-articular position by aspirating fluid if joint distended.

Step 3Skin Incision

Make horizontal stab incision with 11-blade, 5-10mm long, centered on the needle entry point. Horizontal incision is parallel to IPBSN.

Step 4Trocar/Sheath Introduction

Insert blunt trocar with sheath, aiming toward intercondylar notch. Feel the capsule give way as you enter the joint. Do NOT force.

Step 5Scope Introduction

Remove trocar, insert 4mm 30-degree arthroscope. Connect camera, light source, and inflow. Confirm intra-articular position.

Step 3: Anteromedial Portal (Working) - UNDER DIRECT VISION

AM Portal Steps

Step 1Visualize Target

From AL portal, look toward the medial compartment. Identify the medial femoral condyle, anterior horn of medial meniscus, and fat pad.

Step 2Needle Localization

Insert spinal needle under direct visualization 1cm medial to the patellar tendon at joint line level. Watch the needle enter the joint on screen.

Step 3Optimize Position

The needle should enter above the anterior horn of medial meniscus, avoiding fat pad entrapment. Adjust entry point if needed before skin incision.

Step 4Skin Incision

Make horizontal stab incision over needle, 5-10mm long. Remove needle and keep incision open.

Step 5Portal Cannula

Insert blunt trocar through the portal under direct vision. Can use portal cannula or work with instruments directly.

AM Portal Safety

The AM portal must be created under direct arthroscopic vision. Blind AM portal placement risks injury to the anterior horn of the medial meniscus, articular cartilage, or fat pad. Always localize with spinal needle first and visualize the needle entering the joint.

The working portal position is confirmed, and instruments can now be triangulated.

Extensile Techniques and Options

When standard two-portal arthroscopy provides insufficient access, several options exist:

1. Additional Anterior Portals

Far medial/lateral portals: For ACL femoral tunnel drilling, improved triangulation
Trans-notch visualization: Insert scope through one side, work from opposite

2. Posterior Portals (see above)

Posteromedial and posterolateral when required
Use transillumination for safety

3. Inside-Out and Outside-In Techniques

Meniscal repair needles: Pass inside-out for posterior horn suturing
Outside-in repair: For anterior and middle third meniscal tears

4. Mini-Open Conversion

If arthroscopic procedure fails, can extend portal to small arthrotomy
Example: Mini-open meniscal repair at posterior horn

5. Pump Pressure Optimization

Increase pump pressure (up to 60mmHg) for bleeding control
Use with caution - compartment syndrome risk with extravasation

Portal Options for Specific Procedures

Complications and Management

Knee Arthroscopy Complications

Compartment Syndrome - Key Points:

Cause: Fluid extravasation through capsular defect into calf or thigh
Risk factors: Prolonged surgery, high pump pressures, capsular tears
Recognition: Increasing leg swelling, pain out of proportion, tense compartments
Prevention: Monitor leg compartments, limit pump pressure, limit OR time
Treatment: Immediate fasciotomies - orthopedic emergency

Recognize Extravasation Early

During knee arthroscopy, periodically palpate the calf and thigh for swelling. If significant extravasation is detected, lower pump pressure, consider switching to gravity inflow, and expedite the procedure. Postoperatively, monitor for compartment syndrome symptoms.

Instrument Breakage:

Shavers, graspers, and other instruments can break intra-articularly
Always perform instrument count before and after procedure
Broken fragments require immediate retrieval - loose body causing damage
May require additional portals or mini-open approach

Evidence Base

FIDELITY Trial - Arthroscopic Partial Meniscectomy vs Sham Surgery

Sihvonen et al • N Engl J Med (2013)

Clinical Implication: APM provides NO benefit over sham surgery for degenerative meniscal tears in middle-aged/elderly patients. Consider non-operative management first.

Limitation: Selected population (degenerative tears), may not apply to traumatic tears or young patients.

METEOR Trial - Physical Therapy vs APM for Meniscal Tears

Katz et al • N Engl J Med (2013)

Clinical Implication: Physical therapy is a reasonable first-line treatment for degenerative meniscal tears. Reserve surgery for mechanical symptoms or PT failure.

Limitation: High crossover rate, combined population with OA may confound results.

Meniscal Repair Success Rates - Meta-analysis

Nepple et al • Am J Sports Med (2012)

Clinical Implication: Meniscal repair should be performed when tear characteristics are favorable (red-red zone, vertical tear, young patient, concurrent ACL surgery).

Limitation: Heterogeneous studies, variable definitions of healing and failure.

Portal Placement and IPBSN Injury

Mochizuki et al • Knee Surg Sports Traumatol Arthrosc (2014)

Clinical Implication: Use horizontal skin incisions parallel to the IPBSN. Counsel all patients about risk of anterolateral knee numbness.

Limitation: Cadaveric study, may not reflect surgical reality.

Compartment Syndrome After Knee Arthroscopy

Marti et al • Arthroscopy (2001)

Clinical Implication: Monitor leg compartments during arthroscopy. Limit pump pressure to less than 60mmHg. If extravasation detected, expedite procedure and observe postoperatively.

Limitation: Case series, low overall incidence makes RCT impractical.

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

Scenario 1: Describe Standard Knee Arthroscopy Portal Placement

EXAMINER

"The examiner asks: 'Describe your technique for establishing portals for knee arthroscopy.'"

EXCEPTIONAL ANSWER

I would position the patient supine with the leg hanging free off the side of the table or in a leg holder, with the knee flexed 70-90 degrees. A thigh tourniquet would be applied if desired. I start with the **anterolateral portal** which is my viewing portal. I palpate the soft spot 1cm lateral to the patellar tendon at the level of the inferior pole of patella. I first localize with an 18-gauge spinal needle to confirm intra-articular placement. Then I make a horizontal stab incision with an 11-blade to protect the infrapatellar branch of the saphenous nerve which runs horizontally. I insert the blunt trocar with sheath aiming toward the intercondylar notch, then introduce the 4mm 30-degree arthroscope and establish inflow. The **anteromedial portal** is then created UNDER DIRECT VISION. I visualize the medial compartment through the scope, then insert a spinal needle 1cm medial to the patellar tendon at the joint line, watching it enter the joint on the monitor. I optimize its position to enter above the anterior horn of medial meniscus, then make my skin incision over the needle and introduce the working cannula under direct visualization. I never create the AM portal blind.

VIVA SCENARIOModerate

Scenario 2: Complications of Knee Arthroscopy

EXAMINER

"A patient develops severe calf pain and swelling 4 hours after knee arthroscopy. The calf is tense to palpation. What is your concern and management?"

EXCEPTIONAL ANSWER

This presentation raises immediate concern for **compartment syndrome** of the leg secondary to fluid extravasation during arthroscopy. This is an orthopedic emergency. I would immediately assess all compartments of the leg for tension and check for pain with passive stretch of the toes. I would assess neurovascular status including pulses, capillary refill, and sensation. If compartment syndrome is suspected, I would not wait for compartment pressure measurements - clinical diagnosis is sufficient to act. Management involves **immediate four-compartment fasciotomy** of the leg. I would take the patient back to theater urgently and perform bilateral incision fasciotomies, releasing anterior, lateral, superficial posterior, and deep posterior compartments. The wounds are left open with negative pressure dressing and planned delayed primary closure or skin grafting at 48-72 hours. In terms of prevention, during knee arthroscopy I monitor pump pressure (less than 60mmHg), periodically palpate the leg for swelling, limit operative time, and recognize capsular tears that may increase extravasation risk.

VIVA SCENARIOModerate

Scenario 3: Portal Options for ACL Reconstruction

EXAMINER

"You are performing an ACL reconstruction. What portals do you need and why?"

EXCEPTIONAL ANSWER

For ACL reconstruction I would use **three to four portals**. First, the standard **anterolateral portal** for visualization - this is my primary viewing portal for the entire case. Second, the **anteromedial portal** for initial diagnostic arthroscopy and some instrumentation. Third, depending on my femoral tunnel drilling technique, I may need an **accessory anteromedial or far AM portal**. For anatomic ACL reconstruction with independent tunnel drilling, a far AM portal (more medial and slightly higher) allows better access to the femoral footprint. This is created under direct vision with spinal needle localization, positioned to allow the drill guide to reach the anatomic femoral insertion. I may also use a **superolateral portal** for additional outflow to maintain visualization during drilling and graft passage. The tibial tunnel is created through a separate small anterior incision, not a true arthroscopic portal. For two-incision techniques, the femoral tunnel may be drilled outside-in through a small lateral incision. The key principle is that portal position directly affects ability to achieve anatomic tunnel placement.

VIVA SCENARIOStandard

Scenario 4: Evidence for Meniscal Surgery

EXAMINER

"A 52-year-old presents with a degenerative medial meniscal tear on MRI. They ask whether arthroscopy will help. How do you counsel them?"

EXCEPTIONAL ANSWER

This is an important discussion given recent evidence. I would explain that for **degenerative meniscal tears** in middle-aged patients, particularly when associated with early osteoarthritis, the evidence does NOT support routine arthroscopic partial meniscectomy. I would cite the **FIDELITY trial** which showed that APM was no better than sham surgery for degenerative tears, and the **METEOR trial** which showed physical therapy was equally effective as surgery for these tears. Therefore, I recommend **non-operative management as first-line treatment**: physiotherapy for quadriceps strengthening, weight loss if applicable, activity modification, and analgesia. I would reserve arthroscopy for patients who: (1) have true mechanical symptoms such as locking that prevents full extension, (2) have failed a 3-6 month trial of conservative treatment, or (3) have a clearly traumatic tear pattern on MRI with an acute onset. I would also counsel that even with surgery, the natural history of the underlying osteoarthritis will continue, and surgery does not slow arthritis progression. For this patient, I would recommend a trial of physiotherapy and reassess in 3 months.

MCQ Practice Points

Portal Order Question

Q: Which portal should be established first during knee arthroscopy? A: The anterolateral portal is always established first as the viewing portal. The anteromedial portal is then created under direct arthroscopic vision. Never create the AM portal blind.

IPBSN Question

Q: What nerve is most commonly injured during knee arthroscopy, and what is the consequence? A: The infrapatellar branch of the saphenous nerve (IPBSN) is injured in 10-30% of cases, causing anterolateral knee numbness. Prevention: horizontal skin incisions, staying at joint line level.

Evidence Question

Q: According to the FIDELITY trial, what is the role of arthroscopic partial meniscectomy for degenerative meniscal tears? A: The FIDELITY trial showed APM is no better than sham surgery for degenerative meniscal tears. Non-operative management with physiotherapy is recommended first-line.

Compartment Syndrome Question

Q: How is compartment syndrome prevented during knee arthroscopy? A: Monitor pump pressure (keep less than 60mmHg), periodically palpate leg compartments for swelling, limit operative time, and recognize capsular tears that increase extravasation risk.

Meniscal Repair Zone Question

Q: Which zone of the meniscus has the best healing potential and why? A: The red-red (peripheral) zone has the best healing potential due to its blood supply from the perimeniscal capillary plexus. The red-white (middle) zone has intermediate potential, while the white-white (central) zone has poor healing due to avascularity.

Patient Positioning Question

Q: What are the two main positioning options for knee arthroscopy, and when is each preferred? A: Supine with leg hanging (60-90° flexion) is preferred for most procedures - allows gravity to open joint. Supine with leg support is used for ACL reconstruction when tibial tunnel drilling requires stable position. Both options should maintain thigh support.

Australian Context

Knee arthroscopy is one of the most common orthopedic procedures in Australia with over 100,000 procedures performed annually. However, rates have declined significantly following publication of high-quality RCTs (FIDELITY, METEOR) demonstrating limited benefit for degenerative meniscal tears compared to sham surgery or physiotherapy. Australian practice has shifted toward meniscal repair over resection in younger patients with traumatic tears, aligned with international guidelines.

The Australian orthopaedic community has been at the forefront of implementing evidence-based practice changes, with many surgeons now offering structured rehabilitation as first-line treatment for degenerative tears. This represents a significant shift from historical practice patterns and aligns with recommendations from the Royal Australasian College of Surgeons regarding informed consent for procedures with limited evidence of efficacy.

Consent considerations in Australia must include explicit discussion of evidence regarding degenerative tears, documentation that non-operative management was offered and declined, and realistic expectation setting regarding outcomes given the natural history of osteoarthritis progression.

Orthopaedic Relevance

For Orthopaedic Operative Surgery station, you must be able to describe portal placement in detail: patient positioning, AL portal first (landmarks, technique), AM portal under direct vision, systematic joint examination sequence, and common complications. Know the evidence regarding APM for degenerative tears and be prepared to discuss non-operative alternatives.