Meniscal Vascular Zones and Repair Potential
The zone a meniscus tear sits in, not the tear pattern alone, predicts whether a repair heals or a partial meniscectomy is the more honest plan.
Takeaways
- The meniscus has three vascular zones, and only the outer third gets a direct blood supply. A perimeniscal capillary plexus fed by the lateral, medial, and middle genicular arteries penetrates the peripheral 10-25% of the meniscus (the red-red zone), leaving the inner white-white zone dependent on diffusion from synovial fluid. (Arnoczky and Warren, Am J Sports Med 1982;10:90-95, PMID 7081532).
- Zone location predicts whether a meniscus repair heals. A 2021 meta-analysis of second-look arthroscopy across 41 studies found complete healing in 84% of red-red zone repairs versus 67% of red-white zone repairs, and red-red location was independently associated with higher healing on metaregression (p=0.026). (Dai et al, Orthop J Sports Med 2021;9:23259671211038289, PMID 34708138).
- No study has ever reported a healing rate for a repaired white-white zone tear. Of the 15 studies in the same meta-analysis that tracked healing by histologic zone, none included a white-white repair cohort, which is the practical reason an isolated avascular-zone tear is usually resected rather than repaired. (Dai et al, Orthop J Sports Med 2021;9:23259671211038289, PMID 34708138).
- Two techniques can push a repair into the avascular zone. Trephination (drilling a vascular access channel to the periphery) gave good or excellent results in 90% of incomplete tears, and adding an exogenous fibrin clot cut isolated-repair failure from 41% to 8%. (Fox et al, Arthroscopy 1993;9:451-455, PMID 8216578; Henning et al, Clin Orthop Relat Res 1990;252:64-72, PMID 2406075).
- Meniscectomy trades symptom relief for joint-destroying contact pressure, and the trade gets worse with more tissue removed. In cadaver knees, total meniscectomy dropped tibiofemoral contact area by about 75% and raised peak local contact stress by about 235%, while partial meniscectomy dropped contact area by only 10% and raised stress by about 65%. (Baratz et al, Am J Sports Med 1986;14:270-275, PMID 3755296).
- The lateral meniscus moves more than twice as far as the medial meniscus during flexion. On 3D MRI reconstruction, posterior horn excursion averaged 11.2 mm for the lateral meniscus against 5.1 mm for the medial meniscus, with the anterior horn more mobile than the posterior horn on both sides. (Thompson et al, Am J Sports Med 1991;19:210-215, PMID 1867329).
- Repairing a meniscus at the same time as ACL reconstruction improves the odds it heals. In the same 2021 meta-analysis, complete healing reached 79% when the meniscus was repaired alongside ACL reconstruction versus 69% for an isolated repair in a stable knee (p=0.029 on metaregression). (Dai et al, Orthop J Sports Med 2021;9:23259671211038289, PMID 34708138).