Orthopaedic Surgery - Meniscus Tear

Basics

A meniscal tear is an acute traumatic or degenerative injury of the fibrocartilaginous meniscus of the knee.

The medial and lateral menisci contribute to:

Load distribution, shock absorption, joint congruity, lubrication, and stability.

Tears vary considerably in morphology, vascularity, stability, and capacity for healing.

Classification

Meniscal tears may be broadly classified as acute traumatic or degenerative.

Acute Tears

Common traumatic tear patterns include:

Longitudinal tears

Radial tears

Flap tears

Longitudinal tears historically account for approximately 50–90% of acute traumatic tears.

Radial tears account for approximately 6%, and flap tears for approximately 4% in older series.

Bucket-Handle Tear

A bucket-handle tear is a displaced longitudinal tear in which the central fragment moves toward the intercondylar notch.

It may cause:

Mechanical locking and inability to achieve full knee extension.

Radial Tear

Radial tears extend perpendicular to the circumferential collagen fibers of the meniscus.

Large radial tears significantly impair the meniscus’s ability to transmit circumferential hoop stresses.

Degenerative Tears

Degenerative tears are commonly:

Horizontal cleavage tears or complex multidirectional tears.

They arise from progressive weakening of the meniscal tissue rather than a single major traumatic event.

Epidemiology

Acute meniscal tears occur predominantly in:

Adolescents, young adults, and athletes.

Degenerative tears become increasingly common after approximately 40 years of age.

Medial Versus Lateral Meniscus

Degenerative tears occur more commonly in the medial meniscus.

In some younger athletic populations, acute traumatic tears of the lateral meniscus are relatively frequent, particularly when associated with ACL injury.

Incidence and Associated ACL Injury

Approximately 30% of acute meniscal tears in older series occur together with an ACL injury.

Meniscal injury is particularly common during twisting trauma that produces rotational instability of the knee.

Asymptomatic Meniscal Tears

A meniscal tear identified on MRI does not necessarily explain the patient’s symptoms.

Meniscal abnormalities become increasingly common with age.

Older studies found meniscal tears on MRI in approximately:

13% of asymptomatic individuals younger than 45 years

and

36% of asymptomatic individuals older than 45 years.

Cadaveric studies have also demonstrated degenerative tears in a large proportion of elderly knees.

Clinical correlation is therefore essential.

Risk Factors

Risk factors include:

Age greater than 40 years

Chronic ACL deficiency

Previous tibial plateau fracture

Knee osteoarthritis

Repetitive deep flexion or twisting activities

Genetics

No specific hereditary pattern has been established for ordinary meniscal tears.

Etiology

Acute Traumatic Tears

Acute tears frequently occur during sports such as:

Football, basketball, wrestling, soccer, and other pivoting activities.

Mechanism

A common mechanism is:

Twisting or pivoting on a weight-bearing knee, particularly during a sudden change in direction.

Flexion combined with rotation can trap the meniscus between the femoral condyle and tibial plateau.

Associated ACL Injury

The same rotational mechanism may rupture the ACL.

Accordingly, every patient with an acute meniscal tear should be examined for associated ligamentous injury.

Degenerative Tears

Degenerative tears result from:

Age-related deterioration, repeated microtrauma, progressive collagen breakdown, and loss of normal meniscal structural integrity.

They may develop with little or no remembered injury.

Associated Conditions

Acute meniscal tears may occur with:

ACL rupture

MCL or other collateral ligament injury

Tibial plateau fracture

Articular cartilage injury

Degenerative tears commonly coexist with osteoarthritis.

Diagnosis

Signs and Symptoms

Common symptoms include:

Joint-line pain

Swelling or recurrent effusion

Catching

Popping

Locking

Buckling or giving way

Symptoms may worsen with:

Pivoting, squatting, kneeling, deep flexion, or twisting.

Joint-Line Pain

Pain is commonly localized to either the:

Medial or lateral joint line.

Posterior horn tears may produce discomfort extending toward the popliteal region when the knee is flexed.

Effusion

Acute traumatic tears may produce an effusion that develops over several hours.

Degenerative tears often cause:

Mild, recurrent, activity-related swelling.

Mechanical Symptoms

Large unstable tears can produce:

Catching, locking, painful clicking, or episodic giving way.

Locked Knee

A displaced bucket-handle tear may mechanically block extension.

The patient may be unable to fully straighten the knee despite attempting to relax.

A true locked knee warrants prompt orthopaedic assessment.

Degenerative Tear Presentation

Degenerative tears commonly present with:

Chronic joint-line pain, intermittent swelling, stiffness, and sharp pain during pivoting or deep flexion.

Many degenerative MRI tears are incidental and should not automatically be assumed to be the source of pain.

History

Important historical features include:

Twisting injury while weight bearing

A sudden change of direction

Pop or snap at injury

Timing of swelling

Mechanical locking or catching

Previous ACL injury

Chronic activity-related pain

Pain with squatting or deep flexion

Physical Examination

A complete knee examination should assess both meniscal pathology and associated ligamentous injury.

Joint-Line Tenderness

Joint-line tenderness is one of the most useful clinical findings.

Tenderness should be assessed along both the:

Medial and lateral joint lines.

Historical studies report a sensitivity around 74%, although accuracy varies according to tear location and patient population.

No single examination maneuver is sufficiently accurate to diagnose every meniscal tear.

Effusion

Assess for:

Joint swelling, ballotable patella, or smaller effusions using milking or blotting maneuvers.

Range of Motion

Document:

Flexion, extension, pain at terminal motion, and any mechanical block.

Loss of full extension may indicate a displaced meniscal fragment.

Ligament Examination

Because acute meniscal injury may coexist with ligament tears, assess:

ACL, PCL, MCL, and LCL stability.

McMurray Test

The McMurray test evaluates the menisci during rotation and extension of the knee.

Medial Meniscus

With the knee maximally flexed:

Externally rotate the tibia, apply valgus stress, and gradually extend the knee.

A painful or palpable click along the medial joint line may indicate a medial meniscal tear.

Lateral Meniscus

With the knee flexed:

Internally rotate the tibia, apply varus stress, and gradually extend the knee.

A painful click or reproduction of symptoms along the lateral joint line suggests lateral meniscal pathology.

Apley Compression Test

The patient lies prone with the knee flexed approximately 90°.

The examiner applies downward compression through the heel while internally and externally rotating the tibia.

Reproduction of joint-line pain or mechanical symptoms may suggest meniscal pathology.

Distraction can be used for comparison because pain relieved by distraction may support an intra-articular rather than ligamentous source.

Imaging

Plain Radiographs

Radiographs do not directly visualize the meniscus but are useful for identifying alternative or associated pathology.

A weight-bearing flexed PA view, often obtained at approximately 30–45° of flexion, is particularly useful for evaluating:

Tibiofemoral joint-space narrowing and early osteoarthritis.

Additional AP, lateral, and patellofemoral views may be obtained.

MRI

MRI is the preferred noninvasive imaging modality for evaluating a suspected meniscal tear.

It can demonstrate:

Tear morphology

Displaced fragments

Meniscal extrusion

Associated ACL or other ligament injury

Cartilage damage

Bone marrow abnormalities

Sensitivity and specificity are generally high, but false-positive findings occur, especially with increasing age and degenerative disease.

MRI findings must therefore be correlated with symptoms and examination.

Arthroscopy

Arthroscopy allows direct visualization of the meniscus and historically has been considered the reference standard for confirming meniscal pathology.

However, arthroscopy is an operative procedure and is not performed solely to establish a diagnosis when clinical examination and MRI are sufficient.

Pathological Findings

The meniscus contains predominantly circumferential collagen fibers that help convert axial compressive loads into circumferential hoop stresses.

Tear Mechanics

Shear and rotational forces can disrupt these fibers.

A tear that completely interrupts the circumferential fiber network, such as a large radial or root tear, can substantially reduce normal meniscal function.

Blood Supply

The peripheral meniscus has the best vascular supply.

Traditionally, the meniscus is divided into:

Red-red peripheral vascular zone

Red-white transitional zone

White-white central avascular zone

Healing Potential

Tears in the peripheral vascular portion have greater capacity to heal.

Tears involving the inner two-thirds have poorer spontaneous healing potential because vascularity is limited.

Degeneration

Repeated microtrauma and aging produce:

Collagen disorganization, loss of tissue strength, mucoid degeneration, and eventual tearing.

Differential Diagnosis

Important alternative or associated diagnoses include:

Articular cartilage lesion

ACL tear

Collateral ligament injury

Plica syndrome

Infrapatellar fat-pad impingement

Osteoarthritis

Patellofemoral chondral disease

Subchondral insufficiency fracture or osteonecrosis

Treatment

General Principles

Initial management is often nonoperative, particularly when there is no true mechanical locking.

Treatment may include:

Activity modification

NSAIDs or other simple analgesics

Ice

Physical therapy

Progressive strengthening

Degenerative Meniscal Tears

Degenerative tears associated with osteoarthritis are generally treated initially with:

Exercise-based therapy, activity modification, weight management when appropriate, and analgesia.

Arthroscopic partial meniscectomy is not routinely beneficial for uncomplicated degenerative tears without persistent mechanical symptoms.

Activity

Weight bearing is generally allowed as tolerated unless another associated injury requires protection.

Activities involving:

Deep squatting, twisting, pivoting, or impact loading

may be temporarily reduced if they reproduce symptoms.

Medication

NSAIDs may be used for pain and inflammation when medically appropriate.

Medication treats symptoms but does not heal the tear itself.

Physical Therapy

Rehabilitation should emphasize:

Restoration of range of motion

Quadriceps and hamstring strengthening

Hip and core strengthening

Neuromuscular control

Gradual return to functional activity

Surgery

Surgical treatment is considered when symptoms remain significant despite appropriate nonoperative care or when a mechanically unstable tear requires intervention.

Indications for Arthroscopy

Possible indications include:

Persistent symptoms affecting work or daily activities

True mechanical locking

Recurrent catching from an unstable tear

Persistent joint-line tenderness and effusion despite treatment

Repairable acute tear in an appropriate patient

Meniscal Preservation

Whenever feasible, preserving functional meniscal tissue is preferred because loss of meniscus increases contact pressure and the long-term risk of osteoarthritis.

Meniscal Repair

Tears most suitable for repair include:

Longitudinal vertical tears

Peripheral vascular-zone tears

Many traumatic tears in younger patients

Meniscal root tears in appropriate patients

Selected radial tears

Classic Repair Criteria

Historically favorable tears include:

Complete vertical tears longer than approximately 10 mm

and

Tears within approximately 3–4 mm of the meniscocapsular junction or peripheral 10–30% of the meniscus.

Modern repair indications are broader because improved techniques permit repair of some radial, complex, and root tears that previously would have been resected.

ACL Reconstruction and Meniscal Repair

Meniscal repairs performed together with ACL reconstruction often have higher healing rates.

Possible reasons include:

Improved knee stability and the biologic environment created by drilling during ACL reconstruction.

Partial Meniscectomy

When a tear is irreparable and remains symptomatic, unstable fragments may be removed with arthroscopic partial meniscectomy.

The objective is to remove only unstable damaged tissue while preserving as much healthy meniscus as possible.

Total Meniscectomy

Total meniscectomy is avoided whenever possible.

Loss of the entire meniscus markedly increases:

Tibiofemoral contact stresses and the risk of accelerated degenerative arthritis.

Postoperative Rehabilitation

After partial meniscectomy, rehabilitation usually progresses relatively quickly.

Goals include:

Reducing swelling

Restoring full motion

Regaining quadriceps strength

Normalizing gait

Return After Partial Meniscectomy

Many patients resume unrestricted activity within approximately several weeks to 2–3 months, depending on symptoms, strength, activity demands, and associated pathology.

Rehabilitation After Meniscal Repair

Recovery following repair is generally slower than after partial meniscectomy because the repair must be protected while healing occurs.

Weight-bearing and flexion restrictions vary according to:

Tear pattern, repair technique, location, and surgeon protocol.

Return to pivoting sports usually occurs only after adequate healing, strength, and functional recovery.

Follow-Up

Patients should undergo progressive:

Range-of-motion exercises, strengthening, gait normalization, and functional rehabilitation.

Return to unrestricted activity should be based on:

Pain, effusion, motion, strength, stability, and sport-specific function rather than time alone.

Prognosis

Many acute traumatic tears have good outcomes when appropriately repaired or treated.

Prognosis is influenced by:

Patient age

Tear pattern

Vascularity

Meniscal tissue quality

ACL stability

Presence of osteoarthritis

Complications

Complications after arthroscopy are uncommon but may include:

Infection

DVT

Neurovascular injury

Portal-site pain or dysesthesia

Persistent swelling

Recurrent meniscal tear

Failure of repair

Progressive osteoarthritis

Nerve Injury

The infrapatellar branch of the saphenous nerve may occasionally be irritated or injured during portal placement, producing:

Localized numbness, pain, or dysesthesia.

Long-Term Degeneration

The risk of osteoarthritis increases when substantial meniscal tissue is lost.

Therefore, the modern guiding principle is:

Preserve and repair the meniscus whenever biologically and mechanically reasonable.

Key Principle

A meniscal tear should not be treated based on the MRI appearance alone.

The most appropriate management depends on the combination of:

Symptoms, mechanical findings, physical examination, tear pattern, patient age, activity level, associated ligament injury, and degree of osteoarthritis.