Why are medial meniscus tears more common than lateral ones?
The two menisci are different shapes, with the medial meniscus being more C-shaped than the O-shaped lateral meniscus.
The medial meniscus is less mobile, and has fibrous bands tethering it to the outer rim. This lack of mobility makes it vulnerable to twisting forces when that leg is on the ground and the upper body is twisting.
Peer-reviewed papersQuote from peer-reviewed paper:
"....In addition, people with ACL-deficient knees are more at risk for the development of medial meniscal tears, especially if ACL reconstruction is delayed for longer than one year from the time of initial injury...."
Citation: Raj MA, Bubnis MA. Knee Meniscal Tears. [Updated 2023 Jul 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Open Access J Sports Med. 2010 Apr 26;1:45-54. doi: 10.2147/oajsm.s7753. PMID: 24198542; PMCID: PMC3781854.
Can a torn medial meniscus repair itself?
The blood supply to the medial meniscus comes in from the outer edges.
So a tear near the outer edge may heal on its own. However, the inner rim has little or no blood supply and tears here heal less readily.
Peer-reviewed papersQuote from peer-reviewed paper:
"....The medial meniscus has its blood supply concentrated in the peripheral 20-30%, whereas the lateral meniscus is perforated by vessels in 10-25% of its periphery....."
Citation: Bhan K. Meniscal Tears: Current Understanding, Diagnosis, and Management. Cureus. 2020 Jun 13;12(6):e8590. doi: 10.7759/cureus.8590. PMID: 32676231; PMCID: PMC7359983.
What is a meniscal repair?
The surgeon may repair a medial meniscus tear with bio-absorbable sutures or fixation devices.
Because of the importance of the meniscus, this may be attempted even if the likelihood of success is not that good. If the surgeon is sure that healing is unlikely, he/she may trim off the torn part but preserve as much of the meniscus as is feasible.
Peer-reviewed papersQuote from peer-reviewed paper:
"When possible, meniscal repair should be performed to try to maintain meniscal integrity and prevent long-term degenerative changes that occur after meniscectomy. When meniscal repair is not possible, partial meniscectomy can be considered saving as much viable meniscal tissue as possible."
Citation: Maffulli N, Longo UG, Campi S, Denaro V. Meniscal tears. Open Access J Sports Med. 2010 Apr 26;1:45-54. doi: 10.2147/oajsm.s7753. PMID: 24198542; PMCID: PMC3781854.
What is a meniscal substitution?
Sometimes a meniscus is simply too damaged to save, and the surgeon may propose removing it altogether and replacing it with a donor meniscus or a manufactured substitute.
Peer-reviewed papersQuote from peer-reviewed paper:
"....Different types of meniscal substitutes, including allografts, collagen, and synthetic and biodegradable scaffolds have been used in experimental and clinical studies....Synthetic or collagen meniscal scaffold implants are gaining favor....."
Citation: Bryceland JK, Powell AJ, Nunn T. Knee Menisci. Cartilage. 2017 Apr;8(2):99-104. doi: 10.1177/1947603516654945. Epub 2016 Jul 7. PMID: 28345407; PMCID: PMC5358830.