Meniscus Injury: Anatomy, Biomechanics, Assessment, Management and Rehabilitation

Prof. Dr Akram Fathy’s lecture covers the menisciMeniscusOne of two semicircular fibrocartilaginous structures between the femoral condyles and the tibial plateau of the knee: the medial and the lateral meniscus. of the knee in six parts: (1) anatomy and blood supply, (2) biomechanicsBiomechanicsHow forces act on and through the body during movement.General meaning, not from the slides (seven functions), (3) mechanism of injury, (4) clinical assessment, (5) classification and management, and (6) rehabilitationRehabilitationExercise and treatment that restore function after injury or surgery.General meaning, not from the slides and return to sportReturn to sport (RTS)Going back safely to training and competition, judged using return-to-sport criteria..

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Objectives and Roadmap

Lecture aim

To equip students with the knowledge and clinical reasoning needed to assess, diagnose and manage meniscalMeniscusOne of two semicircular fibrocartilaginous structures between the femoral condyles and the tibial plateau of the knee: the medial and the lateral meniscus. injuries in athletes and active patients, from anatomy and biomechanicsBiomechanicsHow forces act on and through the body during movement.General meaning, not from the slides through evidence-based treatment, rehabilitationRehabilitationExercise and treatment that restore function after injury or surgery.General meaning, not from the slides and safe return to sportReturn to sport (RTS)Going back safely to training and competition, judged using return-to-sport criteria..

Objectives

By the end of the lecture, students should be able to:

1. Describe the anatomy and structural characteristics of the medial and lateral menisci of the knee.
2. Explain the functions and biomechanical roles of the menisci in normal knee joint function.
3. Discuss the common mechanisms, risk factors, and classifications of meniscal injuries.
4. Perform a comprehensive clinical assessment of patients with suspected meniscal tears using history-taking, physical examinationPhysical examinationThe hands-on examination of the patient by the clinician.General meaning, not from the slides, and diagnostic tests.
5. Develop evidence-based treatment and rehabilitation plans, considering both conservativeConservative managementTreatment without surgery.General meaning, not from the slides and surgical management.
6. Apply evidence-based return-to-sport criteria to determine an athlete’s readiness for safe return to training and competition.

Roadmap

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Anatomy of the Menisci

Anatomical background

The menisciMeniscusOne of two semicircular fibrocartilaginous structures between the femoral condyles and the tibial plateau of the knee: the medial and the lateral meniscus. are two semicircularSemilunarShaped like a half-moon or crescent.General meaning, not from the slides fibrocartilaginousFibrocartilageTough, springy cartilage reinforced with collagen fibers, able to cope with both squeezing and pulling forces.General meaning, not from the slides structures located between the femoral condylesFemoral condylesThe two rounded knobs at the lower end of the femur that sit on top of the tibia and menisci.General meaning, not from the slides and the tibial plateauTibial plateauThe flat top surface of the tibia on which the femur and the menisci rest.General meaning, not from the slides. They are firmly attached to the tibiaTibiaThe shin bone, the larger bone of the lower leg.General meaning, not from the slides through the anterior and posterior meniscal rootsMeniscal rootThe anterior or posterior end where the meniscus is firmly anchored to the tibial plateau. Root attachments fix each horn to the tibia. and connected to the joint capsuleJoint capsuleThe fibrous sleeve that surrounds a joint and holds it together.General meaning, not from the slides by the coronary (meniscotibial) ligamentsCoronary (meniscotibial) ligamentsLigaments that connect the periphery of the meniscus to the joint capsule..

Essential for normal knee function by:

1. Increasing joint congruencyCongruencyHow well two joint surfaces fit together. A better fit gives a more stable joint. and stability
2. Distributing loads across the tibiofemoral jointTibiofemoral jointThe main knee joint, where the femur meets the tibia.General meaning, not from the slides
3. Absorbing shockShock absorptionSoaking up and spreading out impact forces from walking, running and jumping.
4. Reducing contact stressContact stressThe force spread over the touching surfaces of femur and tibia. A larger contact area means less stress on the cartilage.General meaning, not from the slides on articular cartilageArticular cartilageThe smooth cartilage that covers the ends of the bones inside a joint.General meaning, not from the slides
5. Assisting joint lubricationLubricationReducing friction between surfaces with a slippery fluid. and nutrition
6. Contributing to proprioceptionProprioceptionThe body's sense of joint position and movement.General meaning, not from the slides

This list has six items, but the roadmap (slide 3), the Part 2 divider (slide 14) and slides 15–18 speak of seven functions (load distribution and hoop stressHoop stressCompression pushes the meniscus outward and its circumferential fibers resist by developing tensile force, turning vertical load into circumferential tension. are counted as functions 1 and 2, and load sharingLoad sharingThe share of the compressive load carried by the menisci, which rises as the knee bends. is function 4). Both numbers are on the slides; the seven-function list is the one in Part 2.

The slide figure is a labelled front view of the knee: patellaPatellaThe kneecap, a small bone at the front of the knee.General meaning, not from the slides (kneecap), femurFemurThe thigh bone.General meaning, not from the slides, lateral collateral ligamentLCLLateral collateral ligament: the ligament on the outer side of the knee.General meaning, not from the slides (LCL), medial collateral ligamentMCLMedial collateral ligament: the ligament on the inner side of the knee. Its deep fibers attach firmly to the medial meniscus.General meaning, not from the slides (MCL), articular cartilage, lateral meniscus, medial meniscus, anterior cruciate ligamentACLAnterior cruciate ligament: a knee ligament that stops the tibia sliding forward on the femur.General meaning, not from the slides (ACL), posterior cruciate ligamentPCLPosterior cruciate ligament: a knee ligament that stops the tibia sliding backward on the femur.General meaning, not from the slides (PCL), fibulaFibulaThe thinner bone running beside the tibia on the outer side of the lower leg.General meaning, not from the slides and tibia.

Gross anatomy

Each meniscus has five parts:

1. Anterior hornHorn of the meniscusThe front (anterior horn) or back (posterior horn) end of the crescent-shaped meniscus.General meaning, not from the slides
2. Body
3. Posterior horn
4. Anterior root attachment
5. Posterior root attachment

Shared structural characteristics:

Slide 6 says both menisci are crescent shaped, but slide 9 describes the lateral meniscus as nearly circular (O-shaped) and the medial as C-shaped. Both statements are on the slides, so the difference is flagged, not resolved.

Collagen architecture and hoop stress

How hoop stress works:

1. Body weight presses the femur against the tibia and compressesCompressionSqueezing together, such as body weight pressing the femur down on the meniscus. In swelling control it also means pressing on the area, for example with a bandage.General meaning, not from the slides the meniscus.
2. Compression tends to push the meniscus outward.
3. Circumferential fibers stretch and develop tensile force that resists this displacementDisplacedMoved out of its normal position.General meaning, not from the slides: the hoop-stress mechanism.

Radial tie fibersRadial tie fibersFibers running from the inner toward the outer border, crossing the circumferential fibers. They reinforce them and prevent longitudinal splitting. run from the inner toward the outer border, crossing the circumferential fibers. They reinforce them and prevent longitudinalLongitudinal tearA tear running parallel to the collagen fibers, splitting the meniscus into inner and outer parts. splitting.

The slide’s tire analogy: circumferential fibers resist expansion, radial fibers hold them together.

The slide figure labels collagenCollagenThe main structural protein of tendons, ligaments and cartilage.General meaning, not from the slides fibers (random orientation), circumferential collagen fibers and radial collagen fibers.

Meniscal structure at a glance

• The superior-view figure shows the horns, roots and ligament relations: ACL, PCL, MCL, LCL, the medial and lateral menisci, and the anterior and posterior horns of each.
• Anterior and posterior root attachments anchor each meniscus to the tibial plateau.
• The second figure shows meniscal cell populations: its labels are superficial cellsSuperficial cellsCells lying in the surface layer of the meniscus. One of the cell populations labelled on the slide figure.General meaning, not from the slides, fibroblast cellsFibroblast cellsCells that make collagen and other fibers in connective tissue. One of the meniscal cell populations shown on the slide.General meaning, not from the slides and chondrocyte cellsChondrocyte cellsCartilage cells that maintain the cartilage matrix. One of the meniscal cell populations shown on the slide.General meaning, not from the slides, with femur, lateral meniscus, fibula and tibia marked.

Medial vs lateral meniscus

Attachments stabilise the menisci and allow coordinated movement with the femur and tibia.

Attachments on the tibial plateau

The menisci are stabilised by attachments to:

• Tibia: anterior and posterior root attachments fix each horn to the plateau.
• Joint capsule: coronary (meniscotibial) ligaments connect the periphery to the capsule.
• Ligaments and muscles: deep fibers of the MCL (medial); popliteus tendonPopliteus tendonThe tendon of the popliteus muscle at the back of the knee. Its relationship with the lateral meniscus makes that meniscus more mobile. relationship at the popliteal hiatus (lateral).

The slide figure is a view of the tibial plateau marking medial and lateral sides, PCL, ACL, the popliteal hiatus, the anterior intermeniscal ligamentAnterior intermeniscal ligamentA ligament that links the front parts of the medial and lateral menisci.General meaning, not from the slides and numbered zones (Zone 1–6, with 2a and 2b).

The slide does not define these numbered zones, so do not assume they match the red/white vascularVascularHaving a blood supply.General meaning, not from the slides zones (Zone 1–3) on slide 12.

Clinical significance of mobility

Preserving meniscal tissue, by repairMeniscal repairSurgery that preserves meniscal function and lowers long-term osteoarthritis risk. It is the preferred surgical option on the slides. whenever possible, protects joint function and lowers long-term osteoarthritisOsteoarthritis (OA)Wear-related joint disease in which cartilage breaks down, causing pain and stiffness.General meaning, not from the slides risk. Both menisci are critical for normal knee biomechanicsBiomechanicsHow forces act on and through the body during movement.General meaning, not from the slides.

Meniscal vascular supply

Blood arrives from the genicular arteriesGenicular arteriesArteries around the knee that supply blood to the meniscus., which form a peri-meniscal capillary plexusPeri-meniscal capillary plexusA network of tiny blood vessels in the joint capsule around the edge of the meniscus. in the capsule. Vessels enter the meniscus only through its peripheral attachment (coronary / meniscotibial ligaments).

Three zones, from the periphery inward (the slide figure labels them Red Zone aka Zone 1, Red-White ZoneRed–white zoneThe middle third of the meniscus: limited blood supply and lower healing potential, though repair may still succeed in selected cases. aka Zone 2 and White Zone aka Zone 3):

Zone, tear pattern and patient factors together decide whether a tear is repaired or trimmed.

Nutrition of the avascular meniscus

1. No direct blood supply: the inner (avascular) portion has no vessels reaching it.
2. DiffusionDiffusionGradual movement of nutrients from where they are plentiful, here the synovial fluid, into tissue that has no blood vessels. from synovial fluidSynovial fluidThe slippery fluid inside a joint that lubricates it and helps feed the cartilage.General meaning, not from the slides: nutrients are taken up primarily from the synovial fluid.
3. Cyclic loading and unloadingCyclic loading and unloadingRepeated pressing and releasing of the meniscus as the knee moves, which drives exchange of nutrients and waste.: knee movement drives exchange of nutrients and metabolic wasteMetabolic wasteWaste products made by cells as they work.General meaning, not from the slides.
4. Tissue stays viable: meniscal tissue maintains its function despite avascularity.

Clinical link: tears in the avascular white–white zone depend on diffusion alone and have minimal capacity to heal.

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Biomechanics: Seven Functions

The menisciMeniscusOne of two semicircular fibrocartilaginous structures between the femoral condyles and the tibial plateau of the knee: the medial and the lateral meniscus. protect the articular cartilageArticular cartilageThe smooth cartilage that covers the ends of the bones inside a joint.General meaning, not from the slides and keep the knee working normally in seven ways.

Load distribution and hoop stress (functions 1 and 2)

• The menisci enlarge the contact areaContact stressThe force spread over the touching surfaces of femur and tibia. A larger contact area means less stress on the cartilage.General meaning, not from the slides between the femoral condylesFemoral condylesThe two rounded knobs at the lower end of the femur that sit on top of the tibia and menisci.General meaning, not from the slides and tibial plateauTibial plateauThe flat top surface of the tibia on which the femur and the menisci rest.General meaning, not from the slides, spreading load and lowering contact stress on the cartilage.
• They convert vertical compressive loadCompressionSqueezing together, such as body weight pressing the femur down on the meniscus. In swelling control it also means pressing on the area, for example with a bandage.General meaning, not from the slides into circumferentialCircumferential fibersCollagen fibers running around the curve of the meniscus. They give tensile strength and resist the outward push of load. tensionTensile forceA pulling force that stretches a material. Tensile strength is how much pulling it can resist.General meaning, not from the slides (hoop stress), directing force outward to the meniscal attachments.

Without them: faster cartilage degenerationDegenerativeCaused by gradual wear and breakdown of tissue over time.General meaning, not from the slides and a higher risk of knee osteoarthritisOsteoarthritis (OA)Wear-related joint disease in which cartilage breaks down, causing pain and stiffness.General meaning, not from the slides.

Shock absorption (function 3)

≈20% drop in the knee’s shock-absorbing capacity after meniscectomyMeniscectomySurgical removal of all or part of a meniscus.General meaning, not from the slides.

1. The fibrocartilageFibrocartilageTough, springy cartilage reinforced with collagen fibers, able to cope with both squeezing and pulling forces.General meaning, not from the slides dissipates forces generated by walking, running and jumping.
2. It absorbs and redistributes impact loads across the joint.
3. This shields the articular cartilage and subchondral boneSubchondral boneThe layer of bone just beneath the joint cartilage.General meaning, not from the slides from excess stress.
4. After meniscectomy, more impact reaches the joint surfaces.

Load sharing during knee motion (function 4)

FlexionFlexionBending the knee.General meaning, not from the slides increases meniscal loading. The share of compressive load carried by the menisci is:

This is why the menisci matter most in squatting, kneeling and stair climbing.

Stability, lubrication and proprioception (functions 5, 6 and 7)

• Function 5, joint stability: better femurFemurThe thigh bone.General meaning, not from the slides–tibiaTibiaThe shin bone, the larger bone of the lower leg.General meaning, not from the slides congruencyCongruencyHow well two joint surfaces fit together. A better fit gives a more stable joint. increases stability, especially in flexion and in ligament-deficient kneesLigament-deficient kneeA knee with a torn or missing ligament, for example after ACL injury. such as after ACLACLAnterior cruciate ligament: a knee ligament that stops the tibia sliding forward on the femur.General meaning, not from the slides injury.
• Function 6, lubrication and nutrition: movement spreads synovial fluidSynovial fluidThe slippery fluid inside a joint that lubricates it and helps feed the cartilage.General meaning, not from the slides over the joint surfaces, reducing friction and helping nutrients reach avascularAvascularHaving no blood vessels. The inner meniscus is avascular and takes nutrients from the synovial fluid. areas of the menisci and cartilage.
• Function 7, proprioception: mechanoreceptorsMechanoreceptorsSensors in the peripheral menisci that sense joint position, movement and load. in the peripheralPeripheryThe outer rim of the meniscus, where it attaches to the joint capsule.General meaning, not from the slides menisci sense joint position, movement and load, supporting neuromuscular controlNeuromuscular controlHow well the nervous system coordinates the muscles to control movement and protect the joint.General meaning, not from the slides and dynamic stabilityDynamic stabilityA joint's stability while it is moving, provided by muscle control.General meaning, not from the slides.

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Mechanism of Injury

Epidemiology: tears are common and often silent

Framingham cohortFramingham cohortThe group of 991 adults older than 50 in the slide's study who had knee MRI regardless of knee pain.: 991 adults older than 50 years who underwent knee MRIMRIMagnetic resonance imaging: a scan that shows soft tissues such as menisci and ligaments.General meaning, not from the slides regardless of knee pain.

Clinical message: a meniscal finding on MRI is not automatically the source of symptoms. Always interpret imagingImagingScans such as MRI that show the inside of the body.General meaning, not from the slides together with the history and examination.

Source on the slide: Englund M, et al. N Engl J Med 2008 (summary: Am Fam Physician 2011, AAFP Journal Club).

Traumatic and degenerative mechanisms

Injuries result from acuteAcuteSudden and recent, as opposed to long-standing.General meaning, not from the slides trauma or degenerativeDegenerativeCaused by gradual wear and breakdown of tissue over time.General meaning, not from the slides change, depending on age, activity level and the condition of the meniscal tissue.

Acute traumatic tears in younger individuals

Typically occur in sports or other high-demand activities with rapid changes of direction, pivoting or landing.

1. Twisting or pivoting: on a weight-bearingWeight bearingPutting body weight through the leg.General meaning, not from the slides knee with the foot firmly planted; commonly produces longitudinalLongitudinal tearA tear running parallel to the collagen fibers, splitting the meniscus into inner and outer parts. or bucket-handle tearsBucket-handle tearA longitudinal tear whose displaced fragment causes locking, loss of terminal extension and catching..
2. RotationRotationTwisting around an axis.General meaning, not from the slides with flexionFlexionBending the knee.General meaning, not from the slides: sudden rotational forces with knee flexion during cutting, pivoting or changing direction.
3. Jump landing: landing with excessive femorotibial rotationFemorotibial rotationTwisting movement between the femur and the tibia.General meaning, not from the slides or axial loadingAxial loadingForce pushing straight down along the long axis of the limb.General meaning, not from the slides.
4. Contact injury: valgusValgusAngled so that the lower leg points outward from the thigh, giving a knock-kneed alignment.General meaning, not from the slides or varusVarusAngled so that the lower leg points inward toward the midline, giving a bow-legged alignment.General meaning, not from the slides stress with rotation or hyperextensionHyperextensionBending a joint backward beyond its normal straight position.General meaning, not from the slides; may cause associated ligament injuries.

Acute injury vs degenerative change

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Clinical Assessment

Clinical presentation of a meniscal tear

Pain, swelling and mechanical symptomsMechanical symptomsLocking, clicking and grinding of the knee. are typical. Severity depends on the type, size and location of the tear.

• Joint line tendernessJoint line tendernessLocalised tenderness along the medial or lateral joint line, one of the most reliable findings of a meniscal tear.: localised tendernessTendernessPain or discomfort when a body part is pressed.General meaning, not from the slides along the medial or lateral joint line is one of the most reliable findings. Best assessed with the knee flexed to 45–90°.
• Joint effusionJoint effusionExtra fluid in the joint that causes swelling.General meaning, not from the slides: mild to moderate swelling may develop within 24–48 hours of injury. It is common, but its absence does not exclude a tear.
• Pain: localised to the affected joint line; aggravated by deep squatting, kneeling, twisting, pivoting or stairs. Posterior hornHorn of the meniscusThe front (anterior horn) or back (posterior horn) end of the crescent-shaped meniscus.General meaning, not from the slides tears hurt in deep flexionFlexionBending the knee.General meaning, not from the slides.
• Mechanical symptoms: lockingLockingTrue knee locking: a displaced meniscal fragment becomes trapped and mechanically prevents full extension., clickingClickingA snapping sound or sensation in the joint during movement.General meaning, not from the slides, grindingGrindingA rough, gritty feeling or sound in the joint during movement.General meaning, not from the slides.

True knee locking

• What it is: a displacedDisplacedMoved out of its normal position.General meaning, not from the slides meniscalMeniscusOne of two semicircular fibrocartilaginous structures between the femoral condyles and the tibial plateau of the knee: the medial and the lateral meniscus. fragment, most commonly from a bucket-handle tearBucket-handle tearA longitudinal tear whose displaced fragment causes locking, loss of terminal extension and catching., becomes trapped between femurFemurThe thigh bone.General meaning, not from the slides and tibiaTibiaThe shin bone, the larger bone of the lower leg.General meaning, not from the slides and mechanically prevents full extensionExtensionStraightening the knee.General meaning, not from the slides.
• How it feels on examination: a firm or springy mechanical block to extension, rather than pain-limited motion.
• Prompt orthopedicOrthopedicRelating to bones, joints and muscles.General meaning, not from the slides evaluation: a displaced tear often needs surgery.

The slide photo shows a model knee with a displaced meniscus (caught in the joint) that blocks the knee from straightening; the inset compares a normal knee (meniscus in normal position) with a locked knee (torn meniscus flipped into the joint causing a block).

Physical examination

No single test confirms or excludes a meniscal tear. Combine history, clinical findings and imagingImagingScans such as MRI that show the inside of the body.General meaning, not from the slides when indicated. The more findings are present, the higher the likelihood of a tear.

Findings that raise suspicion of a tear

Slide 28 repeats the examination findings as a checklist:

• Twisting or pivoting injury to a weight-bearing knee
• Locking, catching or clicking
• Localised joint line tenderness
• Pain on forced hyperextension (modified bounce home test)
• Pain on maximal passive flexion
• McMurray test: pain or palpable/audible click
• Positive Thessaly test

Combine findings: no single sign is diagnostic. Next step: confirm with special tests, and with imaging when it would change management.

Palpation: joint line tenderness

• 45–90° of knee flexion exposes the joint line for palpation of the medial and lateral sides.
• Why it matters: palpation of the medial and lateral joint lines is one of the most valuable components of the physical examinationPhysical examinationThe hands-on examination of the patient by the clinician.General meaning, not from the slides.
• Interpretation: localised tenderness over the involved meniscus is highly suggestive of a tear, particularly with an appropriate injury mechanism.

Slides 25 and 29 call joint line tenderness one of the most reliable or most valuable findings and highly suggestive of a tear, while slides 27, 28 and 31 say no single test or sign is diagnostic. Both are on the slides: use joint line tenderness together with the other findings.

Special tests for meniscal injury

These tests apply compressionCompressionSqueezing together, such as body weight pressing the femur down on the meniscus. In swelling control it also means pressing on the area, for example with a bandage.General meaning, not from the slides, rotationRotationTwisting around an axis.General meaning, not from the slides or stress to the meniscus to reproduce pain, clicking, locking or joint line tenderness.

How accurate are the clinical tests?

PooledMeta-analysisA study that combines the results of several earlier studies.General meaning, not from the slides diagnostic accuracy (%), from a systematic reviewSystematic reviewA structured review that gathers and summarises all the studies on a question.General meaning, not from the slides and meta-analysis:

• Joint line tenderness was the most sensitive (83%). Thessaly at 20° was the most specific (87%).
• The review authors found the evidence heterogeneousHeterogeneousMade up of differing parts, here studies that differ from one another.General meaning, not from the slides and low quality, and concluded that none of these tests alone can be recommended for diagnosis. Use clusters of findings.

Source on the slide: Smith BE, et al. Evid Based Med 2015.

Stoller MRI grading of meniscal degeneration

Grades 1 and 2 are common with aging and often asymptomaticAsymptomaticCausing no symptoms.General meaning, not from the slides: interpret them with the history and examination. Only Grade 3 is a true tear on MRI.

Supporting evidence: in adults older than 50, MRI meniscal damage was found in 35% and about 55% of tears were asymptomatic (Englund 2008).

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Classification of Tears

Tear pattern, location and vascularVascularHaving a blood supply.General meaning, not from the slides zone guide whether a tear can be repaired.

The slide shows two sets of figures: a labelled illustration of the knee with six tear types (intrasubstance/incompleteIntrasubstanceWithin the substance of the meniscus, without reaching its surface.General meaning, not from the slides, horizontalHorizontal tearA tear running parallel to the tibial plateau, splitting the meniscus into superior and inferior parts., radialRadial tearA tear starting at the free inner edge and extending toward the peripheral rim, crossing the collagen fibers., flapFlap tearA tear arising from a horizontal or oblique tear that leaves an unstable fragment., bucket-handleBucket-handle tearA longitudinal tear whose displaced fragment causes locking, loss of terminal extension and catching., complexComplex tearA tear combining two or more tear patterns (longitudinal, horizontal, radial or flap).) and a panel of meniscusMeniscusOne of two semicircular fibrocartilaginous structures between the femoral condyles and the tibial plateau of the knee: the medial and the lateral meniscus. outlines labelled normal, vertical longitudinalLongitudinal tearA tear running parallel to the collagen fibers, splitting the meniscus into inner and outer parts., vertical radial, horizontal, obliqueOblique tearA tear running at a slant across the meniscus.General meaning, not from the slides, complex/degenerativeDegenerativeCaused by gradual wear and breakdown of tissue over time.General meaning, not from the slides.

A. Longitudinal (vertical)

Runs parallel to the collagenCollagenThe main structural protein of tendons, ligaments and cartilage.General meaning, not from the slides fibers, splitting the meniscus into inner and outer parts.

• Usually traumaticTraumaticCaused by a sudden injury.General meaning, not from the slides; common in young athletes.
• Often in the vascular peripheryPeripheryThe outer rim of the meniscus, where it attaches to the joint capsule.General meaning, not from the slides; heals well if repaired early.
• Bucket-handle tear: displacedDisplacedMoved out of its normal position.General meaning, not from the slides fragment causes lockingLockingTrue knee locking: a displaced meniscal fragment becomes trapped and mechanically prevents full extension., loss of terminal extensionTerminal extensionThe last few degrees of straightening the knee.General meaning, not from the slides, catchingCatchingA sensation of the knee snagging during movement.General meaning, not from the slides.

B. Horizontal

Runs parallel to the tibial plateauTibial plateauThe flat top surface of the tibia on which the femur and the menisci rest.General meaning, not from the slides, splitting the meniscus into superior and inferior parts.

• Common in degenerative menisci.
• Seen in middle-aged and older adults.
• May communicate with meniscal cystsMeniscal cystA fluid-filled swelling next to a meniscus.General meaning, not from the slides and extend obliquely.

C. Radial

Starts at the free inner edgeFree edgeThe thin inner border of the meniscus that faces the middle of the joint.General meaning, not from the slides and extends toward the peripheral rim, crossing the collagen fibers.

• Disrupts hoop stressHoop stressCompression pushes the meniscus outward and its circumferential fibers resist by developing tensile force, turning vertical load into circumferential tension. and raises tibiofemoralTibiofemoral jointThe main knee joint, where the femur meets the tibia.General meaning, not from the slides contact pressureContact stressThe force spread over the touching surfaces of femur and tibia. A larger contact area means less stress on the cartilage.General meaning, not from the slides.
• May cause meniscal extrusionMeniscal extrusionThe meniscus being pushed out from its normal position at the edge of the joint.General meaning, not from the slides.
• Large tears act like meniscectomyMeniscectomySurgical removal of all or part of a meniscus.General meaning, not from the slides; repairMeniscal repairSurgery that preserves meniscal function and lowers long-term osteoarthritis risk. It is the preferred surgical option on the slides. whenever feasible.

D. Flap (parrot-beak)

Arises from a horizontal or oblique tear, leaving an unstable fragment.

• Causes intermittent pain and mechanical symptomsMechanical symptomsLocking, clicking and grinding of the knee..
• Fragment may catch between femurFemurThe thigh bone.General meaning, not from the slides and tibiaTibiaThe shin bone, the larger bone of the lower leg.General meaning, not from the slides.
• Mostly degenerative, but can follow trauma.

E. Complex

Combines two or more tear patterns (longitudinal, horizontal, radial or flap).

• Most common in degenerative menisci.
• Frequently associated with osteoarthritisOsteoarthritis (OA)Wear-related joint disease in which cartilage breaks down, causing pain and stiffness.General meaning, not from the slides.
• Extensive tissue involvement; repair is less successful.

F. Root

Disrupts the anterior or posterior rootMeniscal rootThe anterior or posterior end where the meniscus is firmly anchored to the tibial plateau. Root attachments fix each horn to the tibia., so the meniscus loses its fixation to the tibia.

• Most often the posterior root of the medial meniscus.
• Causes extrusion; effects comparable to total meniscectomyTotal meniscectomySurgical removal of the entire meniscus.General meaning, not from the slides.
• Early repair reduces rapid cartilageArticular cartilageThe smooth cartilage that covers the ends of the bones inside a joint.General meaning, not from the slides degeneration and OA.

Comparison of the six patterns

Slide 35 says horizontal tears are “common” in degenerative menisci, while slide 36 says complex tears are “most common” in degenerative menisci. Both wordings are kept as written.

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Management

Meniscal preservation: healing by zone

Why preserve: healthy meniscalMeniscusOne of two semicircular fibrocartilaginous structures between the femoral condyles and the tibial plateau of the knee: the medial and the lateral meniscus. tissue maintains normal knee biomechanicsBiomechanicsHow forces act on and through the body during movement.General meaning, not from the slides, reduces contact stressContact stressThe force spread over the touching surfaces of femur and tibia. A larger contact area means less stress on the cartilage.General meaning, not from the slides and lowers the long-term risk of cartilageArticular cartilageThe smooth cartilage that covers the ends of the bones inside a joint.General meaning, not from the slides degenerationDegenerativeCaused by gradual wear and breakdown of tissue over time.General meaning, not from the slides and osteoarthritisOsteoarthritis (OA)Wear-related joint disease in which cartilage breaks down, causing pain and stiffness.General meaning, not from the slides.

Clinical pearl: repair over meniscectomy

Repair over meniscectomyMeniscectomySurgical removal of all or part of a meniscus.General meaning, not from the slides for repairable tears.

• Best candidates for repair: longitudinalLongitudinal tearA tear running parallel to the collagen fibers, splitting the meniscus into inner and outer parts., bucket-handleBucket-handle tearA longitudinal tear whose displaced fragment causes locking, loss of terminal extension and catching., radialRadial tearA tear starting at the free inner edge and extending toward the peripheral rim, crossing the collagen fibers. and root tearsRoot tearA tear that disrupts the anterior or posterior root, so the meniscus loses its fixation to the tibia. in vascular regions.
• Why preserve tissue: better long-term knee function and a lower risk of osteoarthritis.

Conservative management

Best suited for:

• Small, stable tears
• Tears in the vascular red–red or red–white zones
• Degenerative tears without significant mechanical symptomsMechanical symptomsLocking, clicking and grinding of the knee.
• Minimal pain and preserved knee function
• Patients who are not surgical candidates

Structured program:

• Education and activity modification
• Short-term pain and swelling control
• Progressive physical therapyPhysical therapyTreatment with exercise and hands-on techniques to restore movement and function.General meaning, not from the slides; restore range of motionRange of motionHow far a joint can move.General meaning, not from the slides
• QuadricepsQuadricepsThe large muscle group at the front of the thigh.General meaning, not from the slides, hamstringHamstringThe muscle group at the back of the thigh.General meaning, not from the slides and hip strengthening
• NeuromuscularNeuromuscular controlHow well the nervous system coordinates the muscles to control movement and protect the joint.General meaning, not from the slides and proprioceptiveProprioceptionThe body's sense of joint position and movement.General meaning, not from the slides training
• Gradual return to functional and sporting activities

Many degenerative tears improve with structured rehabilitationRehabilitationExercise and treatment that restore function after injury or surgery.General meaning, not from the slides and do not require surgery.

Surgical management

Considered when conservative treatmentConservative managementTreatment without surgery.General meaning, not from the slides fails or the tear is unlikely to heal without surgery.

Routine arthroscopic partial meniscectomy is discouraged for degenerative tears without mechanical lockingLockingTrue knee locking: a displaced meniscal fragment becomes trapped and mechanically prevents full extension..

Indications for surgical intervention

1. Persistent mechanical locking from a displacedDisplacedMoved out of its normal position.General meaning, not from the slides meniscal fragment
2. Symptomatic bucket-handle or root tears
3. Large, unstable traumatic tears
4. Tears with ACL ruptureRuptureA complete tear or break of a tissue such as a ligament.General meaning, not from the slides or other ligament injury needing reconstruction
5. Persistent pain, swelling or limitation despite 3–6 months of conservative care
6. Young or highly active patients who need normal knee biomechanics restored

Evidence: degenerative tears, surgery vs sham (FIDELITY trial)

• RandomisedRandomised, double-blindPatients are assigned to treatments by chance (randomised), and neither patients nor assessors know who got which treatment (double-blind).General meaning, not from the slides, double-blind, shamSham surgeryA pretend operation, used in trials to test whether the real operation works.General meaning, not from the slides-controlled (Finland).
• 146 patients aged 35–65 with a degenerative medial meniscus tear and no osteoarthritis.
• Arthroscopic partial meniscectomy vs sham surgery.
• Follow-up: 12 months.

Improvement from baseline at 12 months (points):

No significant between-group differences in Lysholm, WOMET or knee pain after exercise. Outcomes after partial meniscectomy were no better than after sham surgery.

Source on the slide: Sihvonen R, et al. N Engl J Med 2013.

Clinical pearl: match treatment to tear type

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Rehabilitation and Return to Sport

Rehabilitation considerations

RehabilitationRehabilitationExercise and treatment that restore function after injury or surgery.General meaning, not from the slides depends on:

• Type of injury
• Treatment approach (conservativeConservative managementTreatment without surgery.General meaning, not from the slides or surgical)
• Healing status of the meniscusMeniscusOne of two semicircular fibrocartilaginous structures between the femoral condyles and the tibial plateau of the knee: the medial and the lateral meniscus.

Primary goals:

• Reduce pain and swelling
• Restore knee function
• Regain muscle strength
• Return safely to daily activities and sport while protecting the healing meniscus

Three pathways: non-operativeNon-operativeWithout surgery.General meaning, not from the slides, after partial meniscectomyPartial meniscectomySurgery that removes only the unstable or irreparable portion of the meniscus, preserving healthy tissue., and after meniscal repairMeniscal repairSurgery that preserves meniscal function and lowers long-term osteoarthritis risk. It is the preferred surgical option on the slides..

Pathway 1: non-operative rehabilitation

For stable or degenerativeDegenerativeCaused by gradual wear and breakdown of tissue over time.General meaning, not from the slides tears without significant mechanical symptomsMechanical symptomsLocking, clicking and grinding of the knee..

Rehabilitation goals:

• Control pain and joint swelling
• Restore full knee range of motionRange of motionHow far a joint can move.General meaning, not from the slides
• Maintain and build quadricepsQuadricepsThe large muscle group at the front of the thigh.General meaning, not from the slides and lower-limb strength
• Improve neuromuscular controlNeuromuscular controlHow well the nervous system coordinates the muscles to control movement and protect the joint.General meaning, not from the slides, balance and proprioceptionProprioceptionThe body's sense of joint position and movement.General meaning, not from the slides
• Return gradually to functional and sporting activities

Avoid early on:

• Deep squatting
• Pivoting and twisting
• Cutting movements
• Running and jumping

Resume the avoided activities gradually as symptoms and function improve.

Pathway 2: after partial meniscectomy

Recovery is generally rapid because no meniscal healing is required. Routine immobilisationImmobilisationKeeping a joint still, for example in a brace.General meaning, not from the slides is not recommended unless the surgeon specifies it.

Pathway 3: after meniscal repair

Weight bearing

Follow the surgeon’s protocol: restrictions vary with tear pattern, repair technique, associated procedures (e.g., ACLACLAnterior cruciate ligament: a knee ligament that stops the tibia sliding forward on the femur.General meaning, not from the slides reconstructionReconstructionSurgery that rebuilds a torn ligament, for example the ACL.General meaning, not from the slides) and any intraoperativeIntraoperativeHappening during an operation.General meaning, not from the slides complications.

Range of motion

Early controlled motion is encouraged; prolonged immobilisation impairs meniscal nutrition and collagenCollagenThe main structural protein of tendons, ligaments and cartilage.General meaning, not from the slides organisation.

• Restore extension gradually
• Progress flexionFlexionBending the knee.General meaning, not from the slides in a controlled manner
• Avoid loaded flexion beyond 90° for the first 6–8 weeks
• Delay deep squatting and kneeling until healed

Two different time frames appear here: weight bearing (limited for the first 4–6 weeks, up to 6–8 weeks for complex or root repairs) and loaded flexion beyond 90° (avoid for the first 6–8 weeks).

Strengthening progression

1. Quadriceps activation and strengthening
2. Closed-chain exercisesClosed-chain exercisesExercises in which the foot stays fixed on the ground or a surface.General meaning, not from the slides within permitted range
3. Balance and proprioceptive training
4. Functional movement training
5. Sport-specific rehabilitation before return to playReturn to sport (RTS)Going back safely to training and competition, judged using return-to-sport criteria.

Limb alignment considerations

Return to sport after meniscal repair

Caveat: criteria across studies are heterogeneousHeterogeneousMade up of differing parts, here studies that differ from one another.General meaning, not from the slides and the evidence is low level (Level IVLevel IV evidenceA low level of evidence, as the slide describes the return-to-sport criteria.). Individualise decisions and follow the surgeon’s protocol.

Source on the slide: Schwach M, et al. Orthop Traumatol Surg Res 2023 (scoping reviewScoping reviewA review that maps the research available on a topic.General meaning, not from the slides of return-to-sport criteria after isolated meniscus sutureSutureA stitch, or the repair of tissue with stitches.General meaning, not from the slides).

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Key Takeaway and Sources

Protect the menisciMeniscusOne of two semicircular fibrocartilaginous structures between the femoral condyles and the tibial plateau of the knee: the medial and the lateral meniscus., protect the cartilageArticular cartilageThe smooth cartilage that covers the ends of the bones inside a joint.General meaning, not from the slides. Losing meniscal tissue exposes the cartilage to higher stress and raises the risk of osteoarthritisOsteoarthritis (OA)Wear-related joint disease in which cartilage breaks down, causing pain and stiffness.General meaning, not from the slides. The menisci spread load, absorb shockShock absorptionSoaking up and spreading out impact forces from walking, running and jumping., and stabilise and lubricate.

Sources cited on the closing slide:

1. Englund M, et al. Incidental meniscal findings on knee MRIMRIMagnetic resonance imaging: a scan that shows soft tissues such as menisci and ligaments.General meaning, not from the slides in middle-aged and elderly persons. N Engl J Med 2008.
2. Summary of Englund 2008. Am Fam Physician 2011 (AAFP Journal Club).
3. Sihvonen R, et al. Arthroscopic partial meniscectomyPartial meniscectomySurgery that removes only the unstable or irreparable portion of the meniscus, preserving healthy tissue. versus sham surgerySham surgeryA pretend operation, used in trials to test whether the real operation works.General meaning, not from the slides for a degenerativeDegenerativeCaused by gradual wear and breakdown of tissue over time.General meaning, not from the slides meniscal tear. N Engl J Med 2013.
4. Smith BE, et al. Special tests for assessing meniscal tears within the knee: a systematic reviewSystematic reviewA structured review that gathers and summarises all the studies on a question.General meaning, not from the slides and meta-analysisMeta-analysisA study that combines the results of several earlier studies.General meaning, not from the slides. Evid Based Med 2015.
5. Schwach M, et al. Return-to-sportReturn to sport (RTS)Going back safely to training and competition, judged using return-to-sport criteria. criteria after isolated meniscus sutureSutureA stitch, or the repair of tissue with stitches.General meaning, not from the slides: scoping reviewScoping reviewA review that maps the research available on a topic.General meaning, not from the slides of the literature. Orthop Traumatol Surg Res 2023.

The slide states that the original lecture content, images and Stoller gradingStoller gradingA 3-grade MRI scale for meniscal signal changes. Only Grade 3 is a true tear. are by Prof. Dr Akram Fathy, and that the slides added in this version are: objectives and roadmap, epidemiologyEpidemiologyThe study of how common a condition is and who it affects.General meaning, not from the slides, test accuracy, FIDELITYFIDELITY trialA randomised, double-blind, sham-controlled trial from Finland: arthroscopic partial meniscectomy versus sham surgery in 146 patients. evidence and return-to-sport criteria.