Residency · Residency · Orthopedic Surgery
Meniscal Injuries: Repair, Preservation, and Transplantation
Introduction
The menisci are C-shaped fibrocartilaginous structures that play critical roles in load transmission, shock absorption, joint stability, lubrication, and proprioception. Meniscal injuries are the most common indication for knee arthroscopy. The treatment paradigm has shifted from routine meniscectomy toward meniscal preservation, given the well-documented association between meniscal loss and accelerated osteoarthritis.
Anatomy and Function
The medial meniscus is semicircular, covering approximately 50% of the medial tibial plateau. It is firmly attached to the deep MCL and joint capsule, making it less mobile. The lateral meniscus is more circular, covering approximately 70% of the lateral tibial plateau, and is more mobile due to the popliteus hiatus and lack of posterior capsular attachment. Together, the menisci transmit 50% of load in extension and 85% of load at 90 degrees of flexion. The vascular supply is divided into three zones: the red-red zone (peripheral one-third) is well-vascularized with the best healing potential, the red-white zone (middle one-third) has intermediate vascularity, and the white-white zone (inner one-third) is avascular with poor healing potential. The meniscal roots anchor the menisci to the tibial plateau and are essential for hoop stress distribution.
Classification of Meniscal Tears
Vertical longitudinal tears run parallel to the circumferential fibers and include bucket-handle tears. Horizontal cleavage tears divide the meniscus into superior and inferior leaves. Radial tears run perpendicular to the circumferential fibers and disrupt the hoop stress mechanism. Complex or degenerative tears are irregular and multidirectional, common in older patients. Root tears occur at or near the meniscal attachment and are functionally equivalent to total meniscectomy.
Clinical Evaluation
Symptoms include joint line pain, mechanical catching or locking, effusion, and giving way. The McMurray test is a rotational maneuver with varus or valgus stress in which a click or pain suggests meniscal pathology. The Thessaly test is performed at 20 degrees of flexion with rotation. MRI provides 90 to 95% sensitivity and specificity for meniscal tears, allowing evaluation of the tear pattern, location, and vascularity zone. A locked knee with inability to fully extend suggests a displaced bucket-handle tear requiring urgent intervention.
Treatment Options
Nonoperative Management
Nonoperative management is appropriate for stable, small (less than 1 cm), partial-thickness tears in the periphery, as well as degenerative tears in patients over 40 without mechanical symptoms. Physical therapy focuses on quadriceps strengthening and activity modification.
Partial Meniscectomy
Partial meniscectomy is indicated for irreparable tears in the avascular zone with mechanical symptoms. The goal is to remove unstable fragments while preserving the maximum amount of stable meniscal tissue. The remaining meniscus is contoured to a stable rim, avoiding aggressive resection. This procedure is associated with increased contact pressures and long-term degenerative changes.
Meniscal Repair
| Technique | Method | Best Indication | Advantages | Risks |
|---|---|---|---|---|
| Inside-out | Vertical mattress sutures via posterior incision | Gold standard; posterior horn/body | Strong fixation; proven outcomes | Neurovascular injury (posterior incision) |
| Outside-in | Needle from capsule into joint | Anterior horn tears | Safe; avoids posterior structures | Limited posterior access |
| All-inside | Suture-based devices placed arthroscopically | Posterior horn tears | No accessory incision; most common today | Device-related chondral injury |
Repair is indicated for tears in the vascular zone (red-red or red-white), vertical longitudinal tears greater than 1 cm, acute tears, and those occurring with concomitant ACL reconstruction, which augments the healing environment. The inside-out technique is the gold standard, using vertical mattress sutures placed from inside the joint through a posterior accessory incision, with a risk of neurovascular injury. The outside-in technique passes a needle from outside the capsule into the joint and is ideal for anterior horn tears. The all-inside technique uses suture-based devices placed entirely arthroscopically and is most commonly used for posterior horn tears. Healing rates reach 80 to 90% with concurrent ACL reconstruction and 60 to 70% with isolated repair.
Meniscal Root Repair
Root tears eliminate hoop stress function, resulting in extrusion and biomechanics equivalent to total meniscectomy. The standard technique is a transtibial pullout repair, which produces the best outcomes when performed before advanced cartilage degeneration (Outerbridge grade less than 3). Medial meniscal posterior root tears are increasingly recognized in middle-aged women.
Meniscal Transplantation
Meniscal transplantation is indicated for a symptomatic meniscal-deficient compartment in young patients (under 50 years) with normal alignment, a stable knee, and intact articular cartilage. Contraindications include advanced osteoarthritis, uncorrected malalignment, obesity, and inflammatory arthropathy. Allografts are size-matched using plain radiographs or MRI measurements. Techniques include bone plug, bone bridge, and soft tissue fixation. Outcomes show 70 to 85% survivorship at 10 years with pain relief and improved function.
Rehabilitation After Meniscal Repair
Rehabilitation involves protected weight-bearing for 4 to 6 weeks, restriction of deep flexion beyond 90 degrees for 6 weeks, and avoidance of squatting, pivoting, or cutting for 4 to 6 months. Return to full activity occurs at 4 to 6 months, which is slower than recovery from partial meniscectomy.
Clinical Pearls
Meniscal preservation should be prioritized whenever possible to prevent accelerated osteoarthritis. Tears in the red-red zone have the best healing potential, and concomitant ACL reconstruction enhances repair healing rates. Root tears are functionally equivalent to total meniscectomy and warrant repair when feasible. Meniscal transplantation is a salvage option for the young, meniscal-deficient knee with preserved cartilage. Aggressive meniscectomy should be avoided because every millimeter of meniscal tissue contributes to load sharing.
References
- Beaufils P, Becker R, Kopf S, et al. "Surgical Management of Degenerative Meniscus Lesions: The 2016 ESSKA Meniscus Consensus." Knee Surgery, Sports Traumatology, Arthroscopy. 2017;25(2):335-346.
- Chahla J, Dean CS, Moatshe G, et al. "Meniscal Ramp Lesions: Anatomy, Incidence, Diagnosis, and Treatment." Orthopedic Journal of Sports Medicine. 2016;4(7):2325967116657815.
- Nepple JJ, Dunn WR, Wright RW. "Meniscal Repair Outcomes at Greater Than Five Years: A Systematic Literature Review and Meta-Analysis." Journal of Bone and Joint Surgery. 2012;94(24):2222-2227.
- LaPrade RF, Matheny LM, Moulton SG, et al. "Posterior Meniscal Root Repairs: Outcomes of an Anatomic Transtibial Pull-Out Technique." American Journal of Sports Medicine. 2017;45(4):884-891.