By Dr. Paul Rothenberg, MD · Orthopedic Surgery · 6 min read
One of the more debated questions in knee surgery is whether a medial meniscus posterior root repair (MMPRR) is worth performing when the patient already has significant cartilage damage in the medial compartment. The concern is intuitive: if the joint surface is already worn down to grade 3 or 4, does repairing the meniscus root still make a meaningful difference?
A recent cohort study with a mean follow-up of five years and a post hoc power exceeding 0.99 provides some of the clearest midterm data yet on this question — and the findings are more encouraging than many surgeons might expect.
Why Medial Meniscus Posterior Root Tears Matter
The posterior root of the medial meniscus is a critical anchoring point. When it tears, the meniscus loses its ability to function as a load-distributing structure — contact pressures in the medial compartment rise sharply, and the joint begins to behave biomechanically as though the meniscus were absent entirely. Left untreated, this accelerates cartilage loss and can progress to end-stage arthritis relatively quickly.
MMPRR has been shown to reverse these harmful biomechanical effects, restoring more normal load distribution across the medial compartment. What has remained less clear is how much benefit patients receive when the cartilage is already significantly damaged at the time of surgery — specifically, whether the presence of Outerbridge grade 3 or 4 chondral loss changes the outcome enough to reconsider repair.
“The overall median survival was 11 years, with an 80% survival rate at 8 years — and no significant differences in failure rate or functional outcomes between patients with minimal and advanced chondral damage.”
About the Study
This was a consecutive cohort study of 170 patients who underwent primary isolated MMPRR at a single institution between July 2003 and November 2022, with a minimum follow-up of one year. Patients were divided into two groups based on intraoperative Outerbridge grading of the medial compartment:
- →Outerbridge grades 0–2 (minimal to moderate chondral loss): 74 patients
- →Outerbridge grades 3–4 (severe to full-thickness chondral loss): 96 patients
Failure was defined as reoperation of the index knee. Patient-reported outcomes (PROs) collected included the International Knee Documentation Committee (IKDC) score, visual analog scale (VAS) for pain, and Marx activity scale scores. PRO analysis required a minimum follow-up of two years. There were no significant baseline differences between the two groups.
What the Results Showed
Survival and Failure Rate
The median survival across the entire cohort was 11 years, with an overall 80% survival rate at 8 years. Broken down by group, survival at 8 years was 80% for grades 0–2 and 7 years for grades 3–4 — a one-year difference that did not reach statistical significance. The overall failure rate was 17.6%, with no significant difference between groups, and the mean time to reoperation was 5.3 years.
Functional Outcomes (IKDC)
The mean postoperative IKDC score was 64.1 ± 23.0. More importantly, the mean change in IKDC score was 27.6 ± 29.7 — well above the established minimal clinically important difference (MCID) of 10.17. Both groups exceeded this threshold, and there were no significant differences between them.
Pain (VAS)
VAS pain scores decreased meaningfully from a preoperative mean of 6.1 ± 2.2 to a postoperative mean of 3.0 ± 3.0 — a clinically significant reduction. Again, no significant differences were found between the two chondral damage groups.
| Outcome | Grades 0–2 | Grades 3–4 |
|---|---|---|
| Survival at 8 years | 80% | 80% at 7 years |
| Failure rate | No significant difference | No significant difference |
| IKDC change | Exceeded MCID | Exceeded MCID |
| VAS pain (pre → post) | 6.1 → 3.0 | No significant difference |
| Median survival | 11 years (overall cohort) | |
What This Means in Practice
The clinical implication is significant. It has been common practice — or at least common hesitation — to hold back on meniscus root repair in patients with advanced chondral damage, on the assumption that the joint is too far gone to benefit meaningfully. This data challenges that assumption directly.
Patients with Outerbridge grades 3 and 4 showed comparable survival, comparable functional improvement, and comparable pain reduction to patients with grades 0 to 2. The repair held up over a meaningful timeframe — a median of 11 years across the cohort — and the degree of functional improvement exceeded what is considered clinically meaningful in both groups.
Equally important is what MMPRR does biomechanically even in an arthritic knee: by restoring more normal load distribution, the repair may slow the rate of further cartilage deterioration, effectively buying the patient meaningful time before more definitive intervention such as osteotomy or arthroplasty becomes necessary.
Key takeaway: Intraoperative Outerbridge classification grades alone should not dissuade orthopedic surgeons from performing MMPRR. Advanced chondral damage at the time of surgery does not preclude durable, clinically meaningful improvement.
Study Limitations Worth Noting
As with any cohort study at level of evidence 3, there are inherent limitations. Patient selection was consecutive but not randomized, meaning unmeasured confounders may influence results. The failure definition — reoperation — captures surgical revision but does not reflect patients who may have experienced functional decline without returning for surgery. Follow-up, while meaningful at a mean of five years, is not yet long enough to draw conclusions about outcomes beyond the 11-year median survival point.
That said, the post hoc power exceeding 0.99 gives confidence that the study was adequately powered to detect differences between groups — and the absence of significant differences is therefore a meaningful finding, not simply a null result from an underpowered analysis.
Frequently Asked Questions
What is a medial meniscus posterior root tear?
The posterior root is the attachment point of the medial meniscus to the tibia at the back of the knee. When this root tears, the meniscus loses its ability to distribute load effectively — contact pressures in the medial compartment rise significantly, accelerating cartilage wear. These tears are often associated with a popping sensation and sudden medial knee pain, frequently in middle-aged patients with some degree of pre-existing degeneration.
What does Outerbridge grading mean?
The Outerbridge classification is a system used during arthroscopy to grade cartilage damage. Grade 0 is normal cartilage. Grade 1 shows softening, grade 2 involves partial-thickness defects, grade 3 represents deep fissuring without exposed bone, and grade 4 indicates full-thickness cartilage loss with exposed subchondral bone. Grades 3 and 4 represent the more advanced end of the spectrum.
If I have arthritis in my knee, can I still benefit from a meniscus root repair?
Based on this data, yes — patients with significant cartilage damage (Outerbridge grades 3 and 4) achieved comparable functional improvement and comparable survival to those with less cartilage damage. Every patient is different, and the decision depends on multiple factors including the degree of deformity, overall joint health, and patient goals — but advanced chondral grading alone is not a reason to avoid the repair.
What happens if the repair fails?
The overall failure rate in this study was 17.6%, with mean time to reoperation of 5.3 years. Reoperation options depend on the clinical picture at that time — possibilities include revision repair, osteotomy to offload the medial compartment, or arthroplasty if arthritis has progressed significantly. Importantly, undergoing MMPRR does not close off these options.
Bottom line: MMPRR is durable and effective regardless of intraoperative chondral status. With an 11-year median survival and clinically meaningful functional improvement in both low- and high-grade chondral damage groups, this data supports offering repair to appropriately selected patients even in the presence of advanced cartilage loss.
Dealing With a Meniscus Root Tear?
If you have been diagnosed with a medial meniscus posterior root tear — or are experiencing medial knee pain with or without a known diagnosis — the right next step is a thorough evaluation to determine whether repair is appropriate for your specific situation, including the condition of the surrounding cartilage.
Dr. Paul Rothenberg is a board-certified, fellowship-trained orthopedic surgeon specializing in knee surgery and joint preservation, serving patients across northern New Jersey. Contact our office to schedule a consultation and review your imaging and options.
References
- Medial Meniscus Posterior Root Repair: Midterm Survival and Patient-Reported Outcomes Based on Intraoperative Outerbridge Grade. Cohort Study; Level of Evidence, 3. Single institution consecutive series, July 2003 – November 2022.
- Allende F, Saad Berreta R, Khan ZA, et al. Establishing the minimal clinically important difference and Patient Acceptable Symptom State after isolated arthroscopic posterior medial meniscal root repair. Orthop J Sports Med. 2025;13(7):23259671251326940. PubMed
- Bernard CD, Kennedy NI, Tagliero AJ, et al. Medial meniscus posterior root tear treatment: a matched cohort comparison of nonoperative management, partial meniscectomy, and repair. Am J Sports Med. 2020;48(1):128-132. PubMed
- Briggs M, Closs JS. A descriptive study of the use of visual analogue scales and verbal rating scales for the assessment of postoperative pain in orthopedic patients. J Pain Symptom Manage. 1999;18(6):438-446. PubMed
- Brophy RH, Wojahn RD, Lillegraven O, Lamplot JD. Outcomes of arthroscopic posterior medial meniscus root repair: association with body mass index. J Am Acad Orthop Surg. 2019;27(3):104-111. PubMed