Preserve When Possible | Repair Better Than Resect | Red-White-White Zones
ISAKOS MENISCUS TEAR CLASSIFICATION
Critical Must-Knows
- Meniscus transmits 70% of knee load - preservation critical to prevent OA
- Blood supply: Red-red (outer third), red-white (middle), white-white (inner) zones
- Repair indications: Peripheral tears under 3mm from rim, length over 10mm, stable rim
- McMurray test: Joint line pain/click with rotation plus flexion-extension
- MRI: Gold standard (90-95% sensitivity) for tear detection and characterization
Clinical Pearls
- "Always try to repair peripheral tears - better long-term outcomes than resection
- "Root tears disrupt hoop stress - treat like complete meniscectomy functionally
- "Degenerative tears in older patients: conservative management first (FIDELITY and METEOR trials)
- "ACL-deficient knee with meniscus tear: stabilize ACL to protect meniscus repair
Clinical Imaging
Imaging Gallery
Critical Meniscus Tear Exam Points
Preserve the Meniscus
The meniscus is not just a vestigial structure - it transmits 70% of load, increases contact area by 50%, and is critical for joint health. Meniscectomy increases contact stress 200-300% and leads to early OA. Always try to repair when possible.
Blood Supply Zones
Red-red zone (0-3mm from periphery): excellent healing. Red-white (3-5mm): moderate. White-white (inner third): avascular, poor healing. This determines repair success and technique selection.
Repair vs Resection
Repair indications: Peripheral tears under 3mm from rim, vertical pattern, length over 10mm, stable tissue. Repair preferred even if technically challenging - better 10-year outcomes. Young patient with repairable tear should get repair.
Root Tears Are Critical
Meniscal root tears disrupt hoop stress mechanism - functionally equivalent to total meniscectomy. Posterior medial root most common. Must repair to restore function. Transtibial pullout technique is gold standard.
Quick Decision Guide - Meniscus Management
| Patient Age | Tear Pattern | Location | Treatment |
|---|---|---|---|
| Young (under 30), active | Vertical/longitudinal | Red-red zone (under 3mm) | Arthroscopic repair (inside-out or all-inside) |
| Young, ACL injury | Peripheral tear | Any repairable location | ACL + meniscus repair (protect repair with stability) |
| Middle age (30-50) | Radial or root | Posterior root | Repair if symptomatic, preserve meniscus |
| Middle age | Complex/degenerative | White-white zone | Conservative first (6 months), partial resection if fails |
| Older (over 50) | Degenerative | Any location | Conservative management first (FIDELITY/METEOR trials) - PT, injections |
REDRED-WHITE Zones - Blood Supply
| R | Red-red zone Outer third (0-3mm): excellent blood supply from perimeniscal capillaries |
| E | Excellent healing 80-90% repair success rate in vascular zone |
| D | Determine repair technique Peripheral tears: inside-out or all-inside sutures |
| R | Red-red zone Outer third (0-3mm): excellent blood supply from perimeniscal capillaries |
| E | Excellent healing 80-90% repair success rate in vascular zone |
| D | Determine repair technique Peripheral tears: inside-out or all-inside sutures |
Hook:Think RED for the outer rim - rich blood supply, excellent healing, direct repair possible
REPAIRREPAIR - Indications for Meniscus Repair
| R | Red-red or red-white zone Peripheral location with blood supply |
| E | Edge distance under 3mm Within 3mm of meniscocapsular junction |
| P | Pattern vertical/longitudinal Tear orientation favorable for sutures |
| A | Acute or traumatic Better healing than chronic degenerative |
| I | Intact peripheral rim Stable tissue quality for suture purchase |
| R | Rim stability maintained No significant extrusion or instability |
| R | Red-red or red-white zone Peripheral location with blood supply | P | Pattern vertical/longitudinal Tear orientation favorable for sutures | I | Intact peripheral rim Stable tissue quality for suture purchase |
| E | Edge distance under 3mm Within 3mm of meniscocapsular junction | A | Acute or traumatic Better healing than chronic degenerative | R | Rim stability maintained No significant extrusion or instability |
Hook:REPAIR guides you to save the meniscus - check all criteria before deciding
BUCKETBUCKET - Bucket-Handle Tear Features
| B | Block to extension Displaced fragment prevents full extension |
| U | Unstable on probing Mobile fragment flips into notch |
| C | Complete longitudinal tear Full-thickness vertical tear |
| K | Knee locks intermittently Mechanical symptoms from displacement |
| E | Extension deficit Loss of terminal extension (10-30 degrees) |
| T | Treatment: repair if possible Preserve meniscus by suturing back |
| B | Block to extension Displaced fragment prevents full extension | C | Complete longitudinal tear Full-thickness vertical tear | E | Extension deficit Loss of terminal extension (10-30 degrees) |
| U | Unstable on probing Mobile fragment flips into notch | K | Knee locks intermittently Mechanical symptoms from displacement | T | Treatment: repair if possible Preserve meniscus by suturing back |
Hook:BUCKET describes the classic displaced longitudinal tear - needs urgent treatment
ROOTROOT - Meniscal Root Tear Significance
| R | Radial tear at attachment Posterior horn attachment to tibia disrupted |
| O | OA risk equivalent to meniscectomy Loss of hoop stress function |
| O | Often medial posterior root Most common location |
| T | Transtibial pullout repair Gold standard surgical technique |
| R | Radial tear at attachment Posterior horn attachment to tibia disrupted | O | Often medial posterior root Most common location |
| O | OA risk equivalent to meniscectomy Loss of hoop stress function | T | Transtibial pullout repair Gold standard surgical technique |
Hook:ROOT tears cut the anchor - functionally removes the whole meniscus stress function
Overview and Epidemiology
Meniscal tears are among the most common knee injuries, occurring across all age groups but with distinct patterns based on mechanism. The menisci are C-shaped fibrocartilaginous structures that play critical roles in load transmission, shock absorption, and joint stability.
Why meniscus preservation matters:
- Transmits 70% of knee load in extension, 50% in flexion
- Increases contact area by 50%, reducing peak stress
- Loss increases contact pressure 200-300%
- Meniscectomy accelerates osteoarthritis development (relative risk approximately 7 for radiographic and symptomatic OA after meniscectomy for a degenerative tear at 16 years; Englund 2003)
Paradigm Shift in Treatment
Historical approach: arthroscopic partial meniscectomy for all symptomatic tears. Modern approach: preserve meniscus tissue whenever possible. Two landmark randomised trials underpin this shift - the FIDELITY trial (Sihvonen et al, NEJM 2013) showed arthroscopic partial meniscectomy was no better than sham surgery for degenerative medial tears without OA, and the METEOR trial (Katz et al, NEJM 2013) showed surgery plus physiotherapy was no better than physiotherapy alone for degenerative tears with mild-to-moderate OA. Repair techniques have also improved, supporting meniscal preservation over resection.
Two distinct populations:
Young/Athletic
- Mechanism: Acute trauma (twisting, pivoting)
- Tear pattern: Vertical, longitudinal, bucket-handle
- Location: Often peripheral (red-red zone)
- Associated injuries: ACL tears (40% have meniscus injury)
- Treatment: Repair strongly preferred
Middle-Aged/Degenerative
- Mechanism: Minor trauma or spontaneous
- Tear pattern: Horizontal cleavage, complex
- Location: Often central (white-white zone)
- Associated findings: Early OA changes
- Treatment: Conservative first, selective resection
Pathophysiology and Mechanisms
Gross anatomy:
| Feature | Medial Meniscus | Lateral Meniscus |
|---|---|---|
| Shape | C-shaped (covers 50-60% of plateau) | O-shaped (covers 70-80% of plateau) |
| Mobility | Less mobile (fixed to MCL) | More mobile (no MCL attachment) |
| Tears | More common (60-70% of tears) | Less common (30-40% of tears) |
| Anterior horn | Attached to tibial plateau anterior | Attached near ACL |
| Posterior horn | Attached to PCL attachment area | Attached near PCL, popliteus hiatus |
Microstructure:
- Fibrocartilage: Type I collagen (90%), proteoglycans, cells (fibrochondrocytes)
- Fiber orientation: Circumferential fibers (resist hoop stress) + radial tie fibers
- Zones: Superficial (contact with femur/tibia), deep (transitional), lamellar (central)
Hoop Stress Mechanism
Load transmission creates circumferential hoop stress in meniscal fibers, like hoops on a barrel. This is why radial tears and root tears are so devastating - they disrupt the circumferential fibers and eliminate the hoop stress function. The meniscus then functions like a "washer with a cut" - it cannot resist extrusion and loses load-bearing capacity.
Blood supply:
The understanding of meniscal blood supply is critical for repair decisions:
| Zone | Distance from Periphery | Vascularity | Healing Potential | Repair Success |
|---|---|---|---|---|
| Red-red | 0-3mm | Excellent (perimeniscal capillary plexus) | Good | 80-90% |
| Red-white | 3-5mm | Moderate (some penetration) | Variable | 60-70% |
| White-white | over 5mm (inner 1/3) | Avascular | Poor | 20-30% |
Source of blood supply:
- Perimeniscal capillary plexus from superior and inferior geniculate arteries
- Penetrates radially from periphery
- Adult meniscus: outer 10-25% has blood supply (children have more)
Why Children Heal Better
Pediatric menisci have blood supply extending further toward the center (red-white zone may extend to 50% in young children). This is why meniscus tears in children have better healing potential and repair should be attempted even for more central tears.
Biomechanical functions:
- Load transmission - 70% of load in extension, 50% in flexion
- Shock absorption - Energy dissipation during loading
- Joint stability - Secondary stabilizer (especially lateral meniscus in ACL-deficient knee)
- Joint lubrication - Synovial fluid distribution
- Proprioception - Mechanoreceptors provide feedback
Classification Systems
International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine (ISAKOS)
Most comprehensive and widely accepted classification:
ISAKOS Meniscus Tear Patterns
| Type | Description | Mechanism | Repairability |
|---|---|---|---|
| Vertical | Parallel to circumferential fibers, longitudinal | Acute trauma, twisting | Good if peripheral |
| Horizontal | Cleavage tear, parallel to tibial plateau | Degenerative, chronic | Poor - usually resect |
| Radial | Perpendicular to circumferential fibers | Acute or chronic | Difficult - consider if root |
| Complex | Combination of patterns | Chronic, degenerative | Variable, usually poor |
ISAKOS also describes:
- Location: Anterior horn, body, posterior horn
- Depth: Partial (superior or inferior surface) vs full-thickness
- Length: Measured in mm
- Quality: Traumatic (good tissue) vs degenerative (poor tissue)
ISAKOS Advantage
The ISAKOS classification is superior because it integrates pattern (determines load-bearing), location (determines vascularity), and tissue quality (determines healing) - all critical for surgical decision-making.
Clinical Assessment
History:
Acute/Traumatic
- Mechanism: Twisting injury, pivoting, deep squat
- Onset: Immediate or within 24-48 hours
- Symptoms: Sharp pain, click, locking, swelling
- Age: Younger patients (under 40)
- Associated: ACL injury (screen carefully)
Chronic/Degenerative
- Mechanism: Minor trauma or spontaneous
- Onset: Gradual (days to weeks)
- Symptoms: Aching, catching, intermittent swelling
- Age: Older patients (over 45)
- Associated: Early OA changes, activity-related pain
Key history questions:
- Locking vs pseudo-locking (true locking = inability to fully extend)
- Mechanical symptoms (catching, clicking with specific movements)
- Swelling pattern (immediate vs delayed)
- Previous knee injuries or surgery
- Activity level and goals
Physical examination:
Meniscus Clinical Tests
| Test | Technique | Positive Finding | Sensitivity/Specificity |
|---|---|---|---|
| McMurray | Flex knee fully, rotate tibia, extend knee | Pain or click at joint line | Sens 70%, Spec 71% |
| Thessaly | Patient stands on one leg, knee flexed ~20deg, rotates body | Pain at joint line | Originally Sens 89%/Spec 97% (Karachalios); Sens ~0.62-0.66/Spec ~0.39-0.55 on independent validation (Blyth 2015) |
| Joint line tenderness | Palpate medial/lateral joint line | Point tenderness | Sens 83%, Spec 83% |
| Apley grind | Prone, flex knee 90deg, rotate with compression | Pain with compression | Sens 61%, Spec 70% |
Thessaly Test - Know the Controversy
The Thessaly test (patient stands on the affected leg with knee flexed about 20 degrees and rotates the body while held for balance) was originally described by Karachalios et al with very high reported accuracy (sensitivity 89%, specificity 97%). However, these figures have not been reproduced: the independent NIHR HTA prospective study (Blyth et al, 2015) found a sensitivity of only 0.62-0.66 and specificity of 0.39-0.55, no better than McMurray, Apley or joint-line tenderness. The exam-safe answer is that no single physical test reliably diagnoses a meniscal tear, and clinical assessment is combined with MRI.
Examination components:
- Inspection: Swelling (effusion), quadriceps wasting (chronic), alignment
- Palpation: Joint line tenderness (most sensitive single finding)
- Range of motion: Extension deficit (bucket-handle), painful arc
- Special tests: McMurray, Thessaly, Apley
- Stability: ACL (Lachman), MCL (valgus stress) - associated injuries
Don't Miss Associated ACL Tear
A substantial proportion of acute ACL tears have an associated meniscus injury, often the lateral meniscus at the time of injury. If clinical examination suggests a meniscus tear in a young patient with acute trauma, always assess ACL stability. Combined injuries need both addressed for optimal outcome.
Differential diagnosis of the painful or mechanical knee
The symptoms attributed to a meniscal tear (joint-line pain, catching, giving way, effusion) overlap with several other conditions, and a meniscal tear seen on MRI is frequently incidental in middle-aged and older patients (Englund, NEJM 2008). Consider the breadth of differentials before attributing symptoms to the meniscus.
Differential Diagnosis - Meniscal Tear Mimics
| Condition | Discriminating features | Key investigation |
|---|---|---|
| Osteoarthritis / chondral lesion | Older patient, diffuse rather than point joint-line pain, crepitus, morning stiffness, often coexists with degenerative tear | Weight-bearing radiographs; MRI cartilage |
| Loose body / osteochondritis dissecans | True intermittent locking that resolves, mechanical catching, younger patient (OCD) | Radiographs, MRI (cartilage and subchondral bone) |
| ACL rupture | Acute pivot injury, haemarthrosis, instability/giving way, positive Lachman | Lachman/pivot-shift, MRI |
| Medial collateral ligament injury | Valgus stress mechanism, tenderness over MCL rather than joint line, valgus laxity | Valgus stress test, MRI |
| Patellofemoral pain / patellar instability | Anterior knee pain, pain on stairs and prolonged sitting, apprehension | Clinical, skyline radiograph |
| Pes anserine bursitis / MCL bursa | Pain and tenderness 4-5 cm below medial joint line, no true mechanical symptoms | Clinical; ultrasound if unclear |
| Subchondral insufficiency fracture (SIFK) | Sudden severe medial pain in older patient, often with a degenerative root tear, marked bone marrow oedema | MRI |
| Septic arthritis / inflammatory arthropathy | Hot swollen knee, fever, systemic upset, raised inflammatory markers | Joint aspiration, bloods |
Investigations
Imaging protocol:
Investigation Pathway
Views: AP standing, lateral, skyline patella, long-leg alignment (if considering surgery)
Purpose: Exclude bony injury, assess OA degree, alignment assessment
Cannot diagnose meniscus tear but rules out differential diagnoses (fracture, OA, loose body)
Sensitivity 90-95%, Specificity 85-90% for meniscus tears
Findings:
- Increased signal intensity within meniscus on T2 (tear)
- Grade 0 = normal, Grade I = intrasubstance (no tear), Grade II = linear signal not reaching surface (no tear), Grade III = signal reaches articular surface (TEAR)
- Meniscus extrusion (over 3mm = root tear or severe degeneration)
- Associated findings (ACL, MCL, bone marrow edema)
True gold standard when performed, but invasive
Used therapeutically more than diagnostically with modern MRI
MRI Grade III is a Tear
Only MRI Grade III signal (linear signal extending to articular surface) represents a true tear. Grade I and II are intrasubstance degeneration without tear - these are NOT surgical indications and are often seen in asymptomatic patients over 45 years old.
MRI interpretation for surgeons:
| Finding | Clinical Significance | Action |
|---|---|---|
| Grade III signal, vertical tear, peripheral | Repairable tear in vascular zone | Arthroscopy for repair |
| Grade III, degenerative, central | Non-repairable, likely chronic | Conservative first per FIDELITY/METEOR trials |
| Root discontinuity or extrusion over 3mm | Root tear with loss of hoop stress | Urgent arthroscopy for root repair |
| Grade I or II signal | Intrasubstance degeneration, NO tear | Not surgical - manage symptoms |
Additional investigations:
- Ultrasound: Operator-dependent, can identify peripheral tears
- Arthro-CT: Rarely used, for patients unable to have MRI
- Standing X-rays: Essential if considering meniscus transplant or realignment surgery
Management Algorithm
Non-Operative Treatment
Indications:
- Degenerative tears in patients over 45 years (FIDELITY and METEOR trials)
- Small stable tears without mechanical symptoms
- Grade I-II MRI signal (intrasubstance degeneration)
- Patient choice or medical comorbidities
Conservative Treatment Protocol
- Activity modification: Avoid aggravating activities (twisting, pivoting, squatting)
- Ice and NSAIDs: Symptom control
- Quadriceps strengthening: Straight leg raises, quad sets
- ROM exercises: Gentle flexion-extension
- Physiotherapy: Comprehensive program
- Strengthening: Progressive resistance (quadriceps, hamstrings)
- Proprioception training: Balance exercises
- Functional training: Sport-specific activities
- Continue strengthening
- Activity modification: Avoid deep squatting
- Weight management: Reduce knee load
- Consider injections: Corticosteroid or hyaluronic acid if persistent symptoms
FIDELITY and METEOR Trials - Changed Practice
Two NEJM 2013 randomised trials reshaped management of degenerative tears. FIDELITY (Sihvonen et al, n=146, age 35-65, no OA) found arthroscopic partial meniscectomy no better than sham surgery at 12 months. METEOR (Katz et al, n=351, age 45+, with mild-to-moderate OA) found surgery plus physiotherapy no better than physiotherapy alone at 6 and 12 months, though 30% of the physiotherapy-only group crossed over to surgery within 6 months. Together they support a trial of physiotherapy first for degenerative tears.
Surgical Technique - Arthroscopic Meniscectomy
When Meniscectomy is Necessary
Indications for partial meniscectomy:
- Irreparable tear (central location, degenerative tissue)
- Failed repair
- Unstable flap tear causing mechanical symptoms
- Complex tear with poor healing potential
Principles:
- Preserve as much meniscus as possible
- Create smooth, stable rim
- Remove only unstable, damaged tissue
- Never perform total meniscectomy (increases OA risk dramatically)
Pre-operative Planning
- Review MRI for tear pattern and location
- Assess degree of OA (if advanced, surgery won't help)
- Counsel patient about preservation vs resection
- Discuss realistic outcomes
- Plan portal placement
Equipment Checklist
- Arthroscopy tower and camera
- Arthroscopic instruments (probes, graspers, punches)
- Meniscal suture devices (if repair possible)
- Meniscal repair needles and sutures
- Basket forceps and shavers
Complications
Complications of Meniscus Surgery
| Complication | Incidence | Prevention/Management |
|---|---|---|
| Neurovascular injury | less than 1% | Safe portal placement, protect structures during inside-out repair |
| Infection | less than 1% | Sterile technique, prophylactic antibiotics |
| DVT/PE | 0.1-0.5% | Early mobilization, thromboprophylaxis in high-risk patients |
| Residual symptoms | 10-20% | Complete tear removal, assess for associated pathology |
| Re-tear after repair | 10-20% | Appropriate patient selection, protect repair with rehab protocol |
| Progressive OA after resection | RR ~7 (degenerative tear, Englund 2003) | Preserve meniscus tissue, counsel patient about long-term risk |
Specific complications by procedure:
Nerve injuries (most significant risk with inside-out technique):
-
Medial meniscus repair:
- Saphenous nerve injury: 2-5% incidence
- Presents as numbness/paresthesia over posteromedial leg
- Prevention: Use retractor to protect neurovascular structures, make safe accessory incision
- Usually resolves over 6-12 months
-
Lateral meniscus repair:
- Peroneal nerve injury: Less than 1% (more serious)
- Risk of foot drop if nerve damaged
- Prevention: Keep knee flexed 90 degrees, use lateral safety incision
- May require nerve exploration if complete injury
Repair failure: 10-20% depending on location and technique
- Red-red zone: 10-15% failure
- Red-white zone: 20-30% failure
- Risk factors: White-white location, poor tissue quality, non-compliance with rehab
Other complications:
- Persistent pain: 5-10%
- Stiffness: 5% (usually responds to PT)
- Postoperative meniscal cyst: Rare
Inside-Out Suture Safety
Always use a safety incision and protect neurovascular structures when tying inside-out sutures. The saphenous nerve (medial) and peroneal nerve (lateral) are at risk. Use a spoon retractor to displace neurovascular bundle away from the capsule.
Proper technique minimizes nerve injury risk while achieving optimal repair strength.
Postoperative Care and Rehabilitation
Partial Meniscectomy Rehabilitation
Meniscectomy Recovery Timeline
- Weight-bearing: As tolerated with crutches (if needed)
- ROM: Immediate mobilization
- Exercises: Quadriceps sets, ankle pumps, straight leg raises
- Ice and elevation
- Pain control: Acetaminophen, NSAIDs
- Mobilization: Full weight-bearing without aids
- ROM: Regain full flexion and extension
- Strengthening: Progressive quadriceps and hamstring strengthening
- Stationary bike: Low resistance
- Pool therapy: If available
- Advanced strengthening: Leg press, step-ups
- Proprioception: Balance board
- Light jogging: If no pain
- Sport-specific training: Begin transition
- Full ROM and strength
- Return to sports: Gradual progression
- Clearance: Pain-free full activity
Return to sport:
- Desk work: 1-2 weeks
- Manual labor: 4-6 weeks
- Non-contact sports: 6-8 weeks
- Contact sports: 8-12 weeks
Meniscectomy allows rapid return but with long-term OA risk trade-off.
Outcomes and Prognosis
Outcomes by treatment:
Meniscus Treatment Outcomes
| Treatment | Success Rate | Return to Sport | Long-term OA Risk |
|---|---|---|---|
| Repair (red-red zone) | 80-90% | 6-9 months | Low (preserved meniscus) |
| Repair (red-white zone) | 60-70% | 9-12 months | Low if successful |
| Partial meniscectomy | 85% (short term) | 3-4 months | High (RR ~7 for OA, Englund 2003) |
| Root repair | 70-85% | 9-12 months | Moderate (better than no repair) |
| Conservative (degenerative) | 60-70% | Variable | Natural progression |
Prognostic factors for repair success:
| Factor | Good Prognosis | Poor Prognosis |
|---|---|---|
| Location | Peripheral (under 3mm) | Central (white-white zone) |
| Tear pattern | Vertical, longitudinal | Horizontal, complex, radial |
| Age | Young (under 30) | Older (over 50) |
| Acuity | Acute trauma | Chronic degenerative |
| ACL status | ACL intact or reconstructed | ACL deficient |
| Tissue quality | Healthy | Degenerative, frayed |
ACL Reconstruction Protects Meniscus Repair
When meniscus repair is performed with concomitant ACL reconstruction, repair success rates are higher (85-90%) compared to isolated meniscus repair (70-80%). The ACL reconstruction restores knee stability and protects the meniscus repair during healing. Always address both injuries together.
Long-term implications:
-
After partial meniscectomy:
- Substantially higher risk of OA development (RR approximately 7 for combined radiographic and symptomatic OA after meniscectomy for a degenerative tear; Englund 2003)
- More extensive resection and degenerative (rather than traumatic) tear type are associated with worse radiographic and symptomatic outcomes
-
After successful repair:
- OA risk approaches normal knee
- Joint preservation maintained
- Better quality of life long-term
Evidence Base and Key Trials
FIDELITY Trial - Arthroscopic Partial Meniscectomy vs Sham Surgery
- Multicentre, double-blind, sham-controlled RCT of 146 patients aged 35-65 with a degenerative medial meniscus tear and NO knee osteoarthritis
- Arthroscopic partial meniscectomy versus sham (diagnostic) arthroscopy
- No significant between-group difference in Lysholm, WOMET or post-exercise pain at 12 months
- Subsequent knee surgery: 2 in the meniscectomy group versus 5 in the sham group
METEOR Trial - Surgery plus Physiotherapy vs Physiotherapy Alone
- Multicentre RCT of 351 patients aged 45+ with a meniscal tear and mild-to-moderate OA on imaging
- Arthroscopic partial meniscectomy plus physiotherapy versus standardised physiotherapy (with optional crossover)
- Mean WOMAC improvement at 6 months similar between groups (difference 2.4 points, 95% CI -1.8 to 6.5)
- 30% of the physiotherapy-only group crossed over to surgery within 6 months
Incidental Meniscal Tears in the General Population (Framingham)
- Population-based MRI study of 991 subjects aged 50-90 (Framingham)
- Prevalence of meniscal tear/destruction rose from 19% (women 50-59) to 56% (men 70-90)
- 61% of subjects with a meniscal tear had no knee pain, aching or stiffness in the prior month
- Tear prevalence was similar in symptomatic and asymptomatic knees with radiographic OA
According to PubMed, the evidence above is drawn from FIDELITY (DOI), METEOR (DOI), Englund 2008 (DOI), Englund 2003 (DOI), Paxton 2011 (DOI), LaPrade root classification 2014 (DOI) and LaPrade root biomechanics 2015 (DOI).
Exam Viva Scenarios
Use these scenarios to practise clinical reasoning and management decisions
Scenario 1: Young Athlete with Traumatic Tear
"A 28-year-old footballer presents with acute knee pain after a twisting injury 3 days ago. He describes a popping sensation and immediate swelling. Examination shows joint line tenderness and positive McMurray test. MRI shows a vertical longitudinal tear of the posterior horn of the medial meniscus, 2cm in length, located 2mm from the meniscocapsular junction. What is your assessment and management?"
Scenario 2: Middle-Aged Patient with Degenerative Tear
"A 52-year-old office worker presents with 3 months of medial knee pain. No specific injury - started after gardening. Examination shows joint line tenderness and positive Thessaly test. MRI shows Grade III signal in the posterior horn of the medial meniscus, horizontal cleavage tear pattern, with underlying Grade 2 chondral changes. How do you manage this patient?"
Scenario 3: Root Tear with Meniscal Extrusion
"A 45-year-old female presents with 6 months of medial knee pain and swelling. She describes a twisting injury at onset. MRI shows discontinuity of the posterior medial meniscus root with 5mm of meniscal extrusion. No significant chondral loss yet. She has failed 3 months of physiotherapy. How do you manage this?"
MCQ Practice Points
Blood Supply Question
Q: What is the blood supply to the meniscus and which zone has the best healing potential? A: The perimeniscal capillary plexus from the geniculate arteries supplies the outer 10-25% of the meniscus. The red-red zone (0-3mm from periphery) has excellent blood supply and 80-90% repair success. The white-white zone (inner third) is avascular with poor healing potential (20-30% success).
Root Tear Question
Q: What is the biomechanical consequence of a meniscal root tear? A: A meniscal root tear disrupts the circumferential collagen fibers and eliminates the hoop stress mechanism, leading to meniscal extrusion. This is functionally equivalent to a total meniscectomy in terms of contact stress distribution. Root tears require repair via transtibial pullout technique to restore function.
Classification Question
Q: According to the ISAKOS classification, which meniscus tear pattern has the best repairability? A: Vertical longitudinal tears in the peripheral (red-red) zone have the best repairability. These tears run parallel to the circumferential fibers and can be sutured effectively. Horizontal cleavage tears and complex tears typically have poor healing potential.
Clinical Test Question
Q: How accurate are clinical tests for meniscus tears? A: No single physical test is reliable in isolation. The Thessaly test was originally reported with sensitivity 89% and specificity 97% (Karachalios), but the independent NIHR HTA validation study (Blyth et al, 2015) found it no better than McMurray, Apley or joint-line tenderness (sensitivity ~0.62-0.66, specificity ~0.39-0.55). Diagnosis combines history, examination and MRI; joint-line tenderness remains a useful single finding.
Evidence Question
Q: What did the landmark 2013 NEJM trials demonstrate about degenerative meniscus tears? A: The FIDELITY trial (Sihvonen et al, NEJM 2013) showed arthroscopic partial meniscectomy was no better than sham surgery at 12 months for degenerative medial tears without OA. The METEOR trial (Katz et al, NEJM 2013) showed surgery plus physiotherapy was no better than physiotherapy alone for degenerative tears with mild-to-moderate OA. Together they support conservative management first for degenerative tears without true mechanical locking.
Treatment Question
Q: What are the long-term consequences of partial meniscectomy? A: Meniscectomy substantially increases the long-term risk of knee osteoarthritis. In Englund's 16-year matched cohort (2003), the relative risk of combined radiographic and symptomatic OA was approximately 7 after meniscectomy for a degenerative tear (and ~2.7 after a traumatic tear). Risk rises with the amount of meniscus removed, because resection reduces contact area and increases peak contact stress. This is why meniscus preservation is critical.
Guidelines, Registries & Global Practice
Global epidemiology
Meniscal tears are among the most common knee injuries worldwide and arthroscopic partial meniscectomy has historically been one of the highest-volume orthopaedic procedures in many health systems. The population burden is dominated by degenerative tears in middle-aged and older adults: in the population-based Framingham MRI study (Englund et al, NEJM 2008; PMID 18784100), the prevalence of a meniscal tear or destruction rose from 19% in women aged 50-59 to 56% in men aged 70-90, and 61% of those with a tear were asymptomatic in the preceding month. Traumatic tears predominate in younger, athletic populations and are commonly associated with ACL rupture.
Guidelines side-by-side
International guidance has converged against routine arthroscopy for degenerative tears since the FIDELITY and METEOR trials, although surgery retains a clear role for true mechanical locking, repairable traumatic tears and root tears.
Meniscal Tear - Guidelines and Recommendations by Body
| Body / region | Position on degenerative tears | Evidence basis |
|---|---|---|
| BMJ Rapid Recommendation (international panel) | Strong recommendation AGAINST arthroscopy for nearly all degenerative knee disease, including degenerative meniscal tears | Linked systematic review of RCTs (incl. FIDELITY, METEOR) |
| ESSKA (European) consensus | Non-operative care first for degenerative meniscal lesions; arthroscopy only after a failed structured programme and selected indications | Formal European consensus on degenerative meniscus |
| AAOS (USA) | Management of OA of the knee guideline discourages arthroscopic lavage/debridement for primary OA; meniscectomy reserved for mechanical symptoms | AAOS clinical practice guideline |
| NICE (UK) | Arthroscopic lavage and debridement not recommended for knee OA unless clear history of mechanical locking | NICE osteoarthritis guidance |
| Choosing Wisely (multiple nations) | Do not perform arthroscopy with partial meniscectomy for degenerative tears without mechanical locking | Specialty-society low-value-care lists |
| Traumatic / repairable / root tears (all bodies) | Preserve the meniscus - repair peripheral vertical tears; repair root tears via transtibial pull-out | FIDELITY/METEOR do not apply; supported by preservation and biomechanical evidence |
Registry and practice variation
There is no dedicated international meniscus registry comparable to arthroplasty registries (e.g. AOANJRR, NJR), so population-level evidence comes from administrative datasets and RCTs rather than implant-style registry survival data. Despite consistent guidance, large practice variation persists: arthroscopic partial meniscectomy rates differ several-fold between and within countries, and uptake of the FIDELITY/METEOR evidence into routine practice has been slow. This gap between evidence and practice is a recognised low-value-care target and a common exam discussion point.
Australian context
In Australia, meniscal surgery is high-volume; sport (AFL, rugby codes, soccer) drives traumatic tears in younger patients while degenerative tears dominate in older adults. Choosing Wisely Australia explicitly discourages arthroscopy with partial meniscectomy for degenerative tears without mechanical locking, mirroring international guidance. Antibiotic prophylaxis follows Therapeutic Guidelines (eTG) - typically cephazolin 2 g IV at induction for arthroscopy with implants. Public-sector waiting times and access to physiotherapy vary by region and should be factored into non-operative planning; workers' compensation and sports-insurance pathways are common for injured workers and athletes respectively.
Medicolegal and Consent Essentials
Consent discussion should cover:
- Re-tear / repair failure: long-term reoperation after repair around 20% versus around 4% after partial meniscectomy (Paxton 2011)
- Infection (less than 1%), DVT/PE (low), and neurovascular injury specific to inside-out repair (saphenous medially, common peroneal laterally)
- Long-term OA risk after meniscectomy (relative risk approximately 7 for degenerative tears; Englund 2003) versus tissue preservation with repair
- Alternatives: for degenerative tears, a structured non-operative programme first, per the FIDELITY and METEOR trials
Common litigation themes: meniscectomy for a degenerative tear without a documented non-operative trial; failure to offer repair for a repairable tear in a young patient; undocumented nerve protection during inside-out repair; and missed associated ACL injury leading to repair failure. Document the repair-versus-resection rationale, tear characteristics, pre- and post-operative neurovascular status, and the rehabilitation plan provided.
MENISCUS TEARS
Clinical summary
Key Anatomy and Function
- •Transmits 70% of knee load in extension, 50% in flexion
- •Blood supply: Red-red (0-3mm), red-white (3-5mm), white-white (inner third - avascular)
- •Medial: C-shaped, less mobile, attached to MCL, more commonly torn
- •Lateral: O-shaped, more mobile, no MCL attachment
- •Hoop stress mechanism: circumferential fibers resist extrusion
Classification (ISAKOS)
- •Vertical: longitudinal/bucket-handle - repairable if peripheral
- •Horizontal: cleavage tear - usually resect
- •Radial: perpendicular to fibers - repair if root
- •Complex: multiple patterns - assess repairability
- •Root tear: disrupts hoop stress = functional total meniscectomy
Clinical Assessment
- •McMurray test: pain/click with rotation + flexion-extension (Sens 70%, Spec 71%)
- •Thessaly test: stand on one leg, rotate body - originally Sens 89%/Spec 97%, but only ~0.62/~0.45 on independent validation (Blyth 2015)
- •Joint line tenderness: 83% sensitive
- •MRI: Grade III signal = tear (Sens 90-95%)
- •Root tear: MRI shows extrusion over 3mm
Treatment Algorithm
- •Young traumatic peripheral tear: REPAIR (inside-out or all-inside)
- •Degenerative tear over 45: CONSERVATIVE first (FIDELITY/METEOR trials)
- •Bucket-handle with locking: URGENT arthroscopy, repair if possible
- •Root tear: Transtibial pullout repair
- •Central white-white tear: Partial meniscectomy if conservative fails
Surgical Pearls
- •Preserve every millimeter possible - even 10% more preservation reduces OA risk
- •Inside-out: gold standard for posterior horn, protect saphenous (medial) or peroneal (lateral)
- •All-inside: faster but watch neurovascular structures
- •Root repair: tunnel at 7mm anterior to PCL, tie over button
- •Protected WB for 6 weeks after repair, 4 weeks non-WB for root
Key Evidence and Outcomes
- •FIDELITY (APM vs sham) and METEOR (surgery+PT vs PT): no benefit of surgery for degenerative tears
- •Meniscectomy for degenerative tear: OA relative risk ~7 at 16 years (Englund 2003)
- •Repair success: 80-90% (red-red), 60-70% (red-white), 20-30% (white-white)
- •Repair with ACL reconstruction: 85-90% success (ACL protects repair)
- •Root repair: 70-85% success, reduces extrusion, slows OA