What is a meniscal tear and how is it treated?

What is a Meniscal Tear?

A meniscal tear is an injury to the semicircular fibrocartilaginous structures in the knee that serve as shock absorbers and load distributors, accounting for over 50% of load transmission across the knee joint. 1

Anatomical Structure and Function

The menisci are composed of a hydrophilic extracellular matrix containing collagen fibers, glycoproteins, and proteoglycans that increase joint congruity and aid in fluid film lubrication. 1 The medial meniscus is more vulnerable to injury due to its intimate attachment to the medial collateral ligament, while the lateral meniscus is more mobile and less prone to tearing except when the ACL is injured. 2

Classification by Mechanism

Traumatic Tears (Younger Patients)

• Result from sudden knee flexion combined with internal or external rotation 2
• More common in active patients participating in cutting and pivoting sports 3
• Often associated with acute injury events 3
• More amenable to repair due to increased healing propensity 4

Degenerative Tears (Older Patients)

• Meniscal tears are common, usually incidental findings, and unlikely to be the cause of knee pain, aching, or stiffness in degenerative knee disease. 3
• Often present without a specific mechanism of injury 2
• Frequently associated with osteoarthritis 3
• Symptoms fluctuate over time and tend to improve naturally after seeing a physician 3

Classification by Tear Pattern and Location

By Vascular Zone

• Red zone (peripheral): Well-vascularized, higher healing potential, more amenable to repair 5, 2
• White zone (central): Avascular, poor healing potential, typically requires meniscectomy if symptomatic 5

By Tear Pattern

• Bucket handle tears: Large longitudinal tears that can displace and cause mechanical locking 6
• Radial tears: Associated with increased risk of cartilage loss (P = 0.017) 4
• Posterior horn tears: Associated with increased risk of cartilage loss (P = 0.031) 4
• Root tears: Particularly significant when involving the posterior horn with advanced osteoarthritis 7

Diagnostic Approach

Key Physical Examination Findings

• Joint line tenderness (medial or lateral) 3, 2
• Knee effusion 2
• McMurray test, Apley test, and "bounce home" maneuver 2
• Positive Lachman test if associated ACL injury 3
• Limited range of motion, particularly inability to fully extend (true locked knee) 3

Imaging

• MRI is the test of choice for confirming meniscal injury and defining type, location, and severity. 2, 8
• Radiographs should be obtained to assess for osteoarthritis 3, 7
• Look for bone bruises on MRI (posterolateral tibial plateau and anterior lateral femoral condyle suggest ACL injury) 3

MRI Predictors of Poor Prognosis

• Subchondral bone marrow edema (P < 0.0001) 4
• Meniscal extrusion (P < 0.001) 4
• Radial tear pattern 4
• Posterior horn involvement 4

Treatment Algorithm

For Degenerative Meniscal Tears with Osteoarthritis

Arthroscopic surgery is NOT recommended for degenerative knee disease with meniscal tears, as it provides less than 15% probability of small or very small improvement in short-term pain and function that does not persist to one year. 3

First-Line Conservative Management

• Structured exercise program (cardiovascular and resistance land-based exercises) 7
• Aquatic exercises for aerobically deconditioned patients 7
• Weight loss for overweight patients 7
• NSAIDs (oral or topical), acetaminophen, tramadol, or intra-articular corticosteroid injections for pain 7
• Patellar taping for short-term relief 7
• Self-management educational programs 7

When Conservative Management Fails

• Total knee arthroplasty is the preferred option for advanced medial compartment osteoarthritis with root tear. 7
• Unicompartmental knee arthroplasty may be considered for isolated medial compartment OA in younger patients, though total knee arthroplasty has lower revision rates 7
• Valgus-producing proximal tibial osteotomy shows similar outcomes to unicompartmental knee arthroplasty in appropriate candidates 7

For Traumatic Tears in Young, Active Patients

Meniscal repair is superior to partial meniscectomy with better functional outcomes and less severe degenerative changes over time. 5

Indications for Surgical Repair

• Young patients with acute traumatic tears 3, 5
• Peripheral (red zone) tears with good vascular supply 5, 2
• Bucket handle tears causing true mechanical locking 6
• Patients participating in cutting and pivoting sports with symptomatic instability 3

Surgical Options

• ACL reconstruction with autograft (median score 8/9) or allograft (median score 7/9) is appropriate for young patients with ACL tears and meniscal pathology. 3
• Meniscal repair for peripheral, well-vascularized tears 5, 2
• Partial meniscectomy only for irreparable tears in avascular zones 5, 1

Recovery Timeline After Arthroscopy

• Recovery typically takes 2-6 weeks 3, 6
• Unable to weight bear for 2-7 days (may need crutches) 3
• Return to sedentary work within 1-2 weeks 3, 9
• Return to physical labor at least 6 weeks 3, 9
• Driving limited for 1-3 weeks 3

Post-Surgical Rehabilitation

• Early mobilization helps reduce pain and improve function 6, 7
• Structured physical therapy focusing on quadriceps and hamstring strengthening 6
• Avoid complete immobilization to prevent muscular atrophy 6
• NSAIDs and cryotherapy (ice through wet towel for 10-minute periods) for pain and swelling 6

Critical Pitfalls to Avoid

• Do not perform arthroscopy for degenerative meniscal tears in patients with osteoarthritis—76% of patients post-meniscectomy develop cartilage loss compared to 38% without surgery (P = 0.0001). 4
• Do not attempt meniscal repair in the setting of advanced osteoarthritis 7
• Do not prescribe lateral heel wedges for medial compartmental OA 7
• Do not rush to arthroscopic procedures without adequate trial of conservative management in degenerative tears 7
• Conservative management is generally not recommended as first-line treatment for bucket handle tears in young patients 6
• Premature return to physically demanding work can lead to re-injury 9

Special Considerations

Exception to Conservative Management

The only clear indication for arthroscopy in degenerative knee disease is patients who are objectively unable to fully extend their knee (true locked knee). 3

Long-Term Consequences

• Meniscectomy places the knee at increased risk of osteoarthritis 1
• Subchondral bone marrow edema and meniscal extrusion are the strongest MRI predictors for cartilage loss in untreated meniscal tears 4
• Removal of meniscus tissue accelerates degenerative changes 5, 4