The journey from silent epidemic to solved mystery: Where we stand and the path forward in meniscal root preservation surgery

Less than a decade ago, a particular subset of meniscal injuries—meniscal root tears—captured the attention of knee preservation surgeons worldwide [4]. It became clear that we were facing a silent epidemic, with these injuries occurring in up to 20% of all meniscal tears diagnosed in clinical practice [4]. Often overlooked, meniscal root tears can have devastating consequences, severely compromising joint stability and long-term function if left untreated.

What was once largely ignored is now front and centre, driving substantial progress in tackling a clinical challenge that had remained underrecognized for years. With increased recognition has come a surge of innovative treatment strategies aimed at restoring function and preventing long-term joint damage. No longer relegated to the sidelines, meniscal root tears are now a key focus for knee preservation surgeons, pushing the boundaries of what we thought possible in joint preservation. This shift in attention has resulted in novel augmentation techniques, enhanced outcomes and a greater understanding of the critical role these tears play in the overall context of knee homeostasis.

Over the past several years, the scientific community has made impressive strides in studying the natural history, diagnosis, biomechanical consequences and repair techniques for both lateral and medial root tears [21, 25]. Key differences between the medial and lateral meniscal roots—both anatomically and biomechanically—have become pivotal to treatment strategies [19]. Notably, lateral root repairs often result in better clinical and radiographic outcomes, largely due to differences in patient demographics and, more critically, the distinct biomechanical properties of lateral roots which also benefit from meniscofemoral attachments [10]. In contrast, medial meniscus posterior root repairs (MMPRR) pose greater challenges, primarily because medial meniscus posterior root tears (MMPRTs) are more common in older patients with age-related degeneration, making the healing process more difficult [10].

The available literature highlights favourable outcomes following meniscal root repair [12]. A systematic review conducted in 2021 reported functional benefits and consistent improvements in clinical outcome scores among 994 patients who underwent MMPRR [2]. But it is not all good news. The authors found that despite these positive clinical outcomes, 49% of patients experienced radiographic progression of at least one grade on the Kellgren–Lawrence scale at a mean follow-up of 4 years, and 23% showed cartilage degeneration progression on MRI over a mean follow-up of 31.6 months [2]. A separate meta-analysis also highlighted that 22% of patients who underwent MMPRR exhibited osteoarthritic progression compared to 66% who underwent meniscectomy [16]. Finally, an experimental study in rabbits confirmed this, showing cartilage damage and meniscal extrusion (ME) persisted following MMPRR [8, 9].

While patient-reported outcomes continue to improve, the suboptimal reduction of post-operative ME remains a significant concern [5, 12]. This distinction between clinical outcomes and radiographic findings has prompted a deeper examination of whether current treatments adequately address post-operative ME, a key factor in osteoarthritis (OA) progression despite technically successful root repairs [22]. Furthermore, residual ME has a negative correlation with post-operative healing status observed during second-look arthroscopy in patients undergoing MMPRR [10, 14]. Given that a higher body mass index is well established as a risk factor for MMPRT and is associated with increased ME [28], it is not surprising that weight loss can enhance meniscal healing after MMPRR [11]. These observations raise two important questions: Are our current treatment approaches adequately targeting ME, and what tools do we have at our disposal to address it?

Early post-operative ME appears to correlate with the progression of cartilage damage over time, underscoring the need for strategies that more effectively mitigate this issue [13, 26]. Innovative procedures are being developed to augment traditional repair techniques and address the persistent challenge of ME. Biomechanical studies have shown that meniscal centralization can restore the load-distributing function of the meniscus and reduce ME [6, 23]. Clinical outcomes from recent studies are promising. For example, a study of 25 patients who underwent MMPRR with centralization suture reported improved clinical outcomes, reduced ME and no progression to OA at a minimum follow-up of 1 year [17]. However, low post-operative MRI follow-up rates limit the ability to draw definitive conclusions regarding the long-term efficacy of this technique.

In addition to clinical risk factors, certain anatomic factors predispose patients to meniscus root injuries. While considerable attention has been given to evaluating the effect of posterior tibial slope (PTS) on anterior cruciate ligament graft tension, recent evidence suggests a potential association between PTS and meniscus root tears [7, 15, 27].

Another significant concern with MMPRR is unaddressed lower leg malalignment. It is well-established that medial ME is associated with varus deformity [1, 26]. Given that root tears may be a consequence rather than the cause of ME [18], it is not surprising that numerous studies have reported a higher incidence of root injuries in patients with varus alignment [1, 20, 26]. Biomechanical data underscore the detrimental effects of uncorrected varus alignment on the medial compartment [24]. Consistent with these findings, clinical research shows that correcting varus alignment concurrently with MMPRR can reduce post-operative ME and improve overall healing rates [3]. The challenge now is determining the optimal threshold for correcting varus alignment and how much ME we need to target. In the meantime, clinicians should tailor their decisions on a case-by-case basis, using the best available evidence to optimize clinical outcomes and enhance joint survival for their patients.

In summary, while considerable progress has been made in meniscal root preservation surgery, many questions remain unanswered. The silent epidemic of meniscal root tears is far from fully resolved, and further research is crucial to refine treatment strategies, tackle challenges such as ME, and ultimately improve long-term joint preservation outcomes. The road ahead is long, but recent progress offers a promising outlook for the future of this evolving field.

Lika Dzidzishvili and Marko Ostojic serve on the Basic Science Committee of the European Society of Sports Traumatology, Knee Surgery, and Arthroscopy (ESSKA). Jorge Chahla reports a relationship with the American Orthopaedic Society for Sports Medicine (AOSSM): Board or committee member; Arthrex, Inc: Paid consultant; Arthroscopy Association of North America (AANA): Board or committee member; CONMED Linvatec: Paid consultant; International Society of Arthroscopy, Knee Surgery, and Orthopaedic Sports Medicine (ISAKOS): Board or committee member; Ossur: Paid consultant; Smith & Nephew: Paid consultant; Paid presenter or speaker.