ACL and Ramp Lesions: When and How

Courtesy: Moira M. McCarthy, Ashok Shyam, IORG, OrthoTV

 

MENISCUS-ANATOMY

GROSS SHAPE

• MEDIAL MENISCUS
  C-shaped with triangular cross section
• LATERAL MENISCUS
  is more circular (the horns are closer together and approximate the ACL)
  covers a larger portion of the articular surface

ATTACHMENT

1. TRANSVERSE (INTERMENISCAL) LIGAMENT
   connects the medial and lateral meniscus anteriorly
2. CORONARY LIGAMENTS: connects the meniscus peripherally

Medial meniscus has less mobility with more rigid peripheral fixation than the lateral meniscus

3.MENISCOFEMORAL LIGAMENT

• connects the meniscus into the substance of the PCL
• originate from the posterior horn of the lateral meniscus and has two components
• Humphrey ligament (anterior)
• Ligament of Wrisberg (posterior)

FUNCTION

1.FORCE TRANSMISSION
the meniscus functions to optimize force transmission across the knee. It does this by

• increasing congruency
  increases contact area leads to decreased point loading
• shock-absorption
  the meniscus is more elastic than articular cartilage, and therefore absorbs shock
  transmits 50% weight-bearing load in extension, 85% in flexion

2.STABILITY

• the meniscus deepens tibial surface and acts as secondary stabilizer
• posterior horn of medial meniscus is the main secondary stabilizer to anterior translation
• lateral meniscus is less stabilizing and has 2X the excursion of the medial meniscus
  THE MENISCI BECOME PRIMARY STABILIZERS IN THE ACL-DEFICIENT KNEE

COMPOSITION

• Made of fibroelastic cartilage
• interlacing network of collagen, proteoglycan, glycoproteins, and cellular elements
• composed of 65-75% water
• Collagen: 90 % Type I collagen
• Fibers: composed of two types of fibers which allow the meniscus to expand under compressive forces and increase contact area of the joint
• radial and longitudinal (circumferential) fibres help dissipate hoop stresses

BLOOD SUPPLY

• middle genicular artery: supply to posterior horns
• medial inferior genicular artery: supplies peripheral 20-30% of medial meniscus
• lateral inferior genicular artery: supplies peripheral 10-25% of lateral meniscus
• central: 75% receive nutrition through diffusion

MENISCAL TEARS

PATHOPHYSIOLOGY

MEDIAL TEARS

• more common than lateral tears
• the exception is in the setting of an acute ACL tear where lateral tears are more common
• degenerative tears in older patients usually occur in the posterior horn medial meniscus

LATERAL TEARS

• more common in acute ACL tears

DESCRIPTIVE CLASSIFICATION
LOCATION

• red zone (outer third, vascularized)
• red-white zone (middle third)
• white zone (inner third, avascular)

POSITION

• anterior, middle, posterior third, root

PRESENTATION

• pain localizing to medial or lateral side
• mechanical symptoms (locking and clicking), especially with squatting
• delayed or intermittent swelling

PHYSICAL EXAM

• Joint line tenderness is the most sensitive physical examination finding
• Effusion

Provocative tests

• APLEY COMPRESSION
  prone-flexion compression
• THESSALY TEST
  standing at 20 degrees of knee flexion on the affected limb, the patient twists with knee external and internal rotation with positive test being discomfort or clicking.
• MCMURRAY’S TEST
  flex the knee and place a hand on medial side of knee, externally rotate the leg and bring the knee into extension. a palpable pop / click + pain is a positive test and can correlate with a medial meniscus tear.

IMAGING
Radiographs

MRI

• MRI is most sensitive diagnostic test, but also has a high false positive rate
• MRI grade III signal is indicative of a tear

Bucket handle meniscal tears indicated by

• “double PCL” sign
• “double anterior horn” sign

RAMP LESION OF THE MEDIAL MENISCUS – OVERVIEW

• The medial meniscus, anchored to the posterior tibial plateau and articular capsule, plays a crucial role in knee joint stability and biomechanics.
• It functions in shock absorption, joint lubrication, nutrient supply, and stabilization, especially compensating for the anterior cruciate ligament (ACL) when it is deficient.
• The term “RAMP LESION” was coined by Michael J. Strobel in 1988 to describe a peripheral longitudinal tear of the medial meniscus, specifically at the meniscocapsular junction.
• This tear often extends along the posterior horn of the medial meniscus, giving it a ramp-like appearance.

MECHANISM OF INJURY

1. In ACL-deficient knees, the medial meniscus—particularly the posterior horn of the medial meniscus (PHMM)—undergoes increased stress due to excessive anterior tibial translation, leading to ramp lesions
2. The ramp lesion involves a tear or detachment at the menisco-capsular junction or the menisco-tibial ligament (MTL), often due to:

a) Semimembranosus tendon contraction

b) Trapping of the meniscus between the femur and tibia

c) Weak connective tissue (e.g., adipose tissue behind the PHMM)

EPIDEMIOLOGY

• MRL is one of the most common lesions associated with ACL injuries.
• Reported incidence varies from 9% to 42%, depending on the study.
• It may also occur in isolated cases, without a full ACL rupture.

CHALLENGES IN DIAGNOSIS

• MRI has low sensitivity, leading to frequent underdiagnosis or misdiagnosis.
• Intraoperative detection may be difficult due to poor visualization and surgeon inexperience.
• Diagnosis often requires arthroscopic confirmation.

CLINICAL SIGNIFICANCE

• Medial Ramp Lesions significantly increase knee laxity.
• If untreated, they contribute to cartilage degeneration over time in ACL-deficient knees.

MANAGEMENT

• Surgical repair is the most common and definitive treatment.
• Early and accurate diagnosis is crucial to prevent long-term joint damage.

RISK FACTORS FOR MENISCAL RAMP LESION (MRL)

MAJOR RISK FACTORS

• Lateral meniscal lesion ? 1.9x risk increase
• ACL reconstruction (ACLR) revision ? 1.8x risk increase
• Age less than 30 years had a higher incidence

INCIDENCE & ASSOCIATED CONDITIONS

• 23.9% of ACL-injured patients had Medial Ramp Lesions
• Higher Medial Ramp Lesions incidence in complete/near-complete ALL tears (p = 0.043).
• Delayed surgery (>3 months) increases risk of meniscal injury (p < 0.001).

ADDITIONAL RISK FACTORS

• Bone contusion on posterior medial tibial plateau
• Steep medial tibial slope
• Increased meniscal slope
• Contact knee injury
• Lateral meniscal tear

PEDIATRIC CONSIDERATIONS

• Increased joint laxity may predispose to meniscal tears.
• However, Medial Ramp Lesions incidence in children/adolescents (23%) is similar to adults.

PRE-OPERATIVE EVALUATION OF MENISCAL RAMP LESION (MRL)
CLASSIFICATION OF MRL (FIVE TYPES) (ARTHROSCOPIC)

• Type 1: Peripheral menisco-capsular tear (stable).
• Type 2: Partial lesion in the superior portion (stable).
• Type 3: Partial inferior lesion (“hidden” tear, unstable).
• 3A: Peripheral vertical tear (MTL connected to PHMM but not medial meniscus).
• 3B: MTL detachment from PHMM.
• Type 4: Complete longitudinal vertical tear in the red-red zone (unstable).
• 4A: No MCL/MTL damage.
• 4B: MCL and MTL detached.
• Type 5: Two separate tears in the red-red zone (stability unclear).

MRI FEATURES & CHALLENGES
MRI FINDINGS:

• Hyperintense fluid-like signals on T2.
• Peripheral irregularities & posterior medial tibial plateau edema.
• MRI sensitivity & specificity fluctuate across studies, leading to frequent misdiagnosis.
• Knee flexion during MRI can improve diagnostic accuracy.
• Chronic ACL injuries may make MRL more visible due to looser tissue attachments.

ADDITIONAL DIAGNOSTIC CONSIDERATIONS
FINOCHIETTO SIGN:

• Specific for posterior longitudinal meniscal tears.
• Not commonly used clinically; can cause discomfort.
• A negative result does not rule out MRL.
• Other meniscal injury tests haven’t been validated for MRL diagnosis.

FINOCHIETTO SIGN This sign consists of a sudden jerk that appears when the free edge of the posterior horn of the medial meniscus is dislocated anteriorly due to the medial condyle interposition when an anterior drawer test is performed on a knee with a ramp lesion, especially when it is associated with an anterior cruciate ligament tear

ARTHROSCOPY AND REPAIR OF MENISCAL RAMP LESION (MRL)
IMPORTANCE OF ARTHROSCOPY

• Only arthroscopy can definitively diagnose or rule out MRL.
• Untreated MRL leads to poor quality of life, loss of function, and inability to perform sports.
• Chronic ACL injuries increase MRL risk ? ACLR should be performed within 3 months to reduce risk.

ARTHROSCOPIC TECHNIQUES FOR DIAGNOSIS

• Posteromedial portal (knee flexed to 90°) ? Most effective for visualization & treatment.
• Other visualization methods:
  Posterolateral transeptal approach
  Transnotch view (useful for Type 4 & 5 MRL)
  Anterior approach (may reveal Type 3 MRL)

A 70° arthroscope inserted into intercondylar space diagnosed 100% of MRL cases.
Anterior inspection (30° scope) had lower detection rates (38–48%).
CHALLENGES: Large knees, subcutaneous fat may require longer arthroscopes, but availability is limited.

MRL REPAIR TECHNIQUES

• All-inside suture with hook device ? Most popular choice.
• Hybrid technique (all-inside + outside-in/inside-out repair)  Used if MRL extends medially.
• Suture hook repair: Captures both meniscus & MTL, ensuring anatomical repair.

COMPARISON OF REPAIR TECHNIQUES

• Inside-out sutures ? Lower failure rate (2%) than all-inside (11%).
• Higher-level study found no statistical difference in healing rates between techniques.

 

WHEN TO REPAIR VS. CONSERVATIVE MANAGEMENT

• Stable, asymptomatic MRLs may not need suturing.
• RCT findings:
  No significant difference in healing/stability between surgical & conservative treatment (p = 0.543).
  Unstable lesions should always be surgically repaired ? Higher healing rates, better knee stability, lower anterior laxity

POST-OPERATIVE PERIOD FOR MENISCAL RAMP LESION (MRL) REPAIR
OUTCOMES OF MRL REPAIR

• Significant improvement in Lysholm Knee Score and subjective scores.
• FAST-FIX™ technique (all-inside repair):
• Post-op arthroscopy showed 87% success rate (40/46 healed fully, 5 healed partially).
• ULTRA FAST-FIX™ had a lower failure rate (1.25%) than FAST-FIX™ 360 (6.25%).
• Combined ACLR & MRL repair: Better knee stability
• ALL reconstruction + ACLR + MRL repair : Lower risk of MRL repair failure than ACLR + MRL repair alone.
• Anterior tibial translation significantly reduced after MRL repair at 90N load (p < 0.05).

RISK FACTORS FOR FAILURE:

• Past ACLR: 3x higher risk of re-operation for meniscal repair (p 90º PROHIBITED FOR AT LEAST 2 WEEKS.
• Non-weight-bearing/toe-touch weight-bearing for the first 2 weeks.
• Partial weight-bearing for 4 weeks.
• Full weight-bearing allowed between weeks 4–12.
• Full range of motion at 6 weeks.
• Return to strenuous activities (running, swimming) at 6 months.
• Some surgeons allow full weight-bearing immediately post-op, but no consensus exists

CONCLUSION

• Lack of awareness and research on Meniscal Ramp Lesions (MRL) has resulted in limited data on its epidemiology, diagnosis, and treatment standards.
• Growing interest in MRL among orthopedic and sports medicine specialists is driving new research and publications.
• Future studies are expected to improve diagnostic accuracy, optimize surgical techniques, and refine post-operative management.
• Encouragement for more doctors to explore this emerging topic and contribute to its growing body of knowledge