Medial meniscus tear is one of the most common internal derangements of the knee joint, resulting from disruption of the fibrocartilaginous structure through traumatic or degenerative mechanisms. The medial meniscus tears more frequently than the lateral meniscus (2:1 ratio) because it is firmly attached to the capsular ligaments and medial collateral ligament (MCL), which restricts its mobility and increases susceptibility to injury. The posterior horn is the most commonly affected region (75%). Tears are classified based on intrameniscal signal changes as Grade 1 (globular), Grade 2 (linear, not reaching the surface), and Grade 3 (reaching the articular surface or extending through the full thickness). Bucket-handle tear is a special form of Grade 3 characterized by displaced meniscal fragment; the double PCL sign is pathognomonic. Acute traumatic tears occur in athletes through pivot/rotational forces, while chronic degenerative tears develop in patients >40 years with underlying osteoarthritis from minor trauma. MRI is the gold standard for diagnosis with 90-95% sensitivity/specificity. Sagittal PD fat-suppressed and coronal sequences evaluate intrameniscal signal increase and morphological disruption.
Age Range
15-60
Peak Age
35
Gender
Male predominant
Prevalence
Very Common
The medial meniscus is a crescent-shaped fibrocartilaginous structure located in the medial compartment of the tibial plateau. It is primarily composed of Type I collagen fibers (60-70%) and proteoglycans. Meniscal vascularity is limited to the peripheral 1/3 red zone, supplied by branches of capsular arteries. The central 2/3 white zone is avascular and nourished by diffusion from synovial fluid. This vascularity difference directly determines healing potential based on tear location: peripheral tears can heal, central tears cannot. In traumatic mechanism, sudden rotation and valgus stress during knee flexion overloads the meniscus — the meniscus trapped between femoral condyle and tibial plateau tears apart. The posterior horn tears most frequently because it bears the greatest load in flexion and has the least mobility. In degenerative mechanism, mucoid degeneration develops in the meniscal matrix with age — collagen fibers weaken, proteoglycan content decreases, and the tissue becomes unable to withstand even normal loads. This degeneration appears on MRI as Grade 1-2 intrameniscal signal increase: mucoid material accumulation shows signal close to water content on T2/PD sequences because proteoglycans trap water molecules and increase local proton density. In bucket-handle tear, the central fragment detaching along the longitudinal tear line displaces into the intercondylar notch and extends anterior to the PCL creating a 'double PCL' appearance. This displaced fragment becomes trapped between articular surfaces producing mechanical symptoms (locking, catching).
On sagittal MRI, a second low-signal band structure is seen in the intercondylar notch just anterior to and parallel to the PCL. This structure represents the central meniscal fragment that has detached along the longitudinal tear line and displaced into the intercondylar notch in a bucket-handle tear. Together with the normal PCL, two separate ligament-like structures are visible — this appearance is termed 'double PCL' and is pathognomonic for medial meniscus bucket-handle tear.
On PD fat-suppressed sagittal images, linear or complex hyperintense signal is seen within the meniscus. Grade 1 shows globular, non-surface-reaching signal increase (asymptomatic degeneration). Grade 2 shows linear signal extending within the meniscus but not reaching the articular surface. In Grade 3, signal reaches at least one articular surface representing a true tear. The posterior horn is the most commonly affected region. Tear pattern may be horizontal, vertical, radial, oblique, or complex. Disruption of meniscal morphology (truncation, irregularity, fragmentation) supports the tear diagnosis.
Report Sentence
A linear hyperintense signal reaching the articular surface is seen in the posterior horn of the medial meniscus, consistent with a Grade 3 tear.
On sagittal PD fat-suppressed images, a low-signal band-like structure is seen in the intercondylar notch just anterior to and parallel to the PCL — this is the displaced bucket-handle fragment. Two separate PCL-like structures are visible together with the normal PCL, hence the name 'double PCL sign.' The displaced fragment is slightly thinner and more irregular than the native PCL. Simultaneously, coronal images show the medial meniscus body as absent or significantly truncated (absent body sign). Bucket-handle tears are 3-4 times more common in the medial meniscus than the lateral.
Report Sentence
A low-signal band structure extending parallel to and anterior to the PCL in the intercondylar notch is seen, with the double PCL sign consistent with a bucket-handle tear.
On T2-weighted images, when the meniscal tear extends to the parameniscal region, parameniscal cyst formation occurs from synovial fluid leaking through the tear line. These cysts are most commonly seen with horizontal tears. They appear as T2 hyperintense localized fluid collections at the outer meniscal margin or meniscocapsular junction. Cyst size varies from a few millimeters to 2-3 cm. The cyst is an indirect sign of underlying meniscal tear, and when present, the meniscus should be carefully evaluated.
Report Sentence
A T2 hyperintense parameniscal cyst measuring approximately ___ mm is seen at the outer margin of the medial meniscus posterior horn, associated with underlying meniscal tear.
On coronal PD or T2 images, displacement of the medial meniscus body more than 3 mm beyond the tibial margin is defined as 'meniscal extrusion.' Extrusion indicates disruption of meniscal structural integrity and loss of load distribution function. It is typically seen in the setting of degenerative horizontal or radial tears, particularly with meniscal root tears. Extrusion degree directly correlates with osteoarthritis progression — >3 mm extrusion predicts cartilage loss and bone marrow lesions. Bilateral (medial and lateral) extrusion is rare and suggests advanced degeneration.
Report Sentence
Approximately ___ mm extrusion of the medial meniscus body is seen on coronal images, consistent with meniscal structural disruption and degenerative tear.
On T2 fat-suppressed or STIR sequences, intraarticular effusion (hyperintense fluid) and reactive bone marrow edema and synovitis findings around the meniscal tear are seen. Acute tears show prominent joint effusion, while chronic degenerative tears show minimal effusion. Synovitis appears as thickened and enhancing synovial membrane. Subchondral bone marrow edema (bone bruise) in the tibial plateau and femoral condyle is an associated finding of axial loading and contusion in traumatic tears.
Report Sentence
Moderate joint effusion is seen in the suprapatellar recess and posterior compartment, with associated subchondral bone marrow edema in the medial compartment.
The normal medial meniscus shows a bow-tie appearance on 2 consecutive sagittal sections through the body region — where anterior and posterior horns converge. In bucket-handle tear, displacement of the central fragment causes loss of this bow-tie appearance — bow-tie is seen in only 0 or 1 slice. This finding is synonymous with the 'absent body' sign and has high sensitivity for bucket-handle tear.
Report Sentence
The bow-tie sign is absent in the body segment of the medial meniscus on sagittal images, a finding consistent with bucket-handle tear.
Criteria
Tear line extends in horizontal (parallel) plane within meniscus, separating superior and inferior leaves
Distinct Features
Most common type in degenerative setting, >40 years, frequent association with parameniscal cyst, usually posterior horn
Criteria
Tear line extends in vertical plane parallel to long axis of meniscus — begins in peripheral region
Distinct Features
Traumatic in young athletes, healing potential if peripheral (red zone), may progress to bucket-handle tear if extends
Criteria
Extension of longitudinal tear with central fragment displacing into intercondylar notch — double PCL sign
Distinct Features
Mechanical symptoms (locking), absent bow-tie sign, flounce sign, surgical urgency, 3-4x more common in medial meniscus
Criteria
Tear line extends perpendicular to free edge of meniscus, disrupting circumferential fibers
Distinct Features
Severely disrupts meniscal function (disrupts circumferential hoop stress), associated with meniscal extrusion and root tears
Criteria
Combination of two or more tear patterns — horizontal+vertical or radial+horizontal
Distinct Features
Usually degenerative, low repair probability, requires partial meniscectomy, associated with advanced age and osteoarthritis
Distinguishing Feature
Lateral meniscus tear is seen in the more mobile lateral meniscus, frequently associated with ACL tear and increased risk in discoid meniscus; medial meniscus tear is more common and usually associated with MCL injury
Distinguishing Feature
Chondral lesion involves articular cartilage surface damage at different location from meniscus; cartilage defect/thinning fills with hyperintense fluid on T2, while meniscal tear shows hyperintense signal within the meniscus
Distinguishing Feature
MCL injury is an extra-articular ligament pathology outside the meniscus characterized by periligamentous edema; O'Donoghue triad (ACL+MCL+medial meniscus) co-occurrence should not be forgotten
Distinguishing Feature
Bone contusion is bone marrow edema in a different anatomic location from the meniscal structure; however, it frequently co-occurs with traumatic meniscal tear and indicates injury mechanism
Urgency
urgentManagement
surgicalBiopsy
Not NeededFollow-up
specialist-referralTreatment of medial meniscus tear is determined by tear type, location, and patient age/activity level. Meniscal repair (suture) is preferred in peripheral (red zone) tears and young patients — preserving the meniscus prevents osteoarthritis development. Partial meniscectomy is performed for central (white zone), degenerative, and complex tears. Bucket-handle tear is a surgical urgency because the displaced fragment produces mechanical symptoms (locking) and delay causes cartilage damage. Conservative treatment (physical therapy, NSAIDs) can only be tried for small, stable, peripheral, and asymptomatic tears. After meniscectomy, medial compartment osteoarthritis risk significantly increases within 5-10 years.
Medial meniscus tears are an important cause of knee pain, swelling, and mechanical symptoms (locking, catching). Degenerative tears may respond to conservative treatment, while traumatic tears and bucket-handle tears may require surgical intervention (arthroscopic meniscectomy or repair).