What are the different types of meniscal injuries?

Types of Meniscal Injuries

Meniscal tears are classified by their anatomical pattern and location, with the most common types being vertical/longitudinal tears, horizontal tears, radial tears, oblique tears, complex tears, bucket-handle tears, root tears, and ramp lesions. 1

Classification by Tear Pattern

Vertical/Longitudinal Tears

• These tears run parallel to the circumferential fibers of the meniscus and are most amenable to repair, particularly when located in the peripheral vascularized zones (red-red or red-white zones) 2
• Bucket-handle tears represent a specific subtype of vertical tears where a large central fragment displaces into the intercondylar notch, often causing mechanical locking of the knee 3, 4

Radial Tears

• These tears extend perpendicular to the circumferential fibers, typically originating from the inner free edge and extending toward the periphery 1
• Radial tears disrupt the critical hoop stress mechanism of the meniscus and have historically been considered difficult to repair 1

Horizontal Tears

• These tears split the meniscus into superior and inferior portions, running parallel to the tibial plateau 1
• Horizontal tears are commonly associated with degenerative processes in older patients rather than acute trauma 3, 5

Oblique Tears

• These tears follow an oblique path through the meniscal tissue and represent a distinct pattern requiring specific repair considerations 1

Root Tears

• Root tears involve detachment of the meniscal attachment points at the anterior or posterior horn insertions 1
• These tears are functionally equivalent to total meniscectomy because they eliminate the meniscus's ability to resist hoop stresses 1

Ramp Lesions

• Ramp lesions occur at the peripheral attachment of the posterior horn of the medial meniscus to the joint capsule 1
• These injuries are frequently associated with ACL tears and may be missed during standard arthroscopic examination 1

Complex/Degenerative Tears

• Complex tears involve multiple tear patterns within the same meniscus 1
• Degenerative tears occur without specific trauma, particularly in middle-aged and elderly patients with underlying cartilage degeneration 5, 2

Classification by Location and Vascularity

Vascular Zones

• Red-red zone: Peripheral 10-25% of the meniscus with excellent blood supply, highest healing potential 2
• Red-white zone: Middle third with moderate vascularity, intermediate healing potential 2
• White-white zone: Inner avascular zone with minimal healing capacity, typically requiring meniscectomy rather than repair 2

Anatomical Location

• Medial meniscus tears are more common than lateral meniscus tears due to the medial meniscus's intimate attachment to the medial collateral ligament, which restricts mobility 3
• The lateral meniscus is more mobile and less prone to isolated tears, except when associated with ACL injuries 3

Clinical Distinction: Traumatic vs. Degenerative

Traumatic Tears

• Result from acute injury with sudden knee flexion combined with rotational forces 3
• Typically occur in younger, active patients with a specific mechanism of injury 3
• More likely to involve peripheral, well-vascularized tissue amenable to repair 2

Degenerative Tears

• Occur in older patients without specific trauma, often associated with underlying osteoarthritis 5, 2
• Frequently present as horizontal or complex tear patterns in the white-white zone 5
• The majority of people over 70 years have asymptomatic degenerative meniscal tears, making clinical correlation essential 6

Important Clinical Considerations

A critical pitfall is that asymptomatic meniscal tears are extremely common in middle-aged and elderly patients—the likelihood of finding a meniscal tear on MRI is similar whether the knee is painful or asymptomatic in patients 45-55 years of age 6

The classification system guides treatment decisions: peripheral vertical tears in vascularized zones warrant repair attempts, while central degenerative tears in avascular zones typically require partial meniscectomy if symptomatic 2, 1