The Guide to Knee Meniscus Tears

The medical machine acts quickly. This is a good thing when situations are dire and life or limb are at stake. However, in less serious situations the expediency of the process may result in a failure to consider all the current evidence regarding diagnosis, treatment options, and their influence on prognosis. The urgency of the process may at first seem reassuring to the patient, instilling confidence that the clinician knows what they are doing. This process should be collaborative, but often it becomes authoritative. Patients are expected to make quick decisions as a layperson to the field. Thus, the process necessitates trust. Trust in the clinician, trust in the decision making, and trust that the information being delivered to them is the best we have (hopefully based on current research evidence).

This discussion could quickly become about informed consent; however, let's focus on prevalent issues in the musculoskeletal world that are often accompanied with imaging and a question of how we should manage this issue. This particular article will be about the knee meniscus. We will set out to answer the question: How significant is the meniscus, and when damaged, what should we do about it based on current best evidence?

So, what is the meniscus?

The meniscus is a fibrocartilaginous structure located in the tibiofemoral joint (i.e., the knee). Its anatomy and location are consistent with a function of shock absorption and force transmission. In each knee there is a meniscus on the medial (inner aspect) and lateral (outer aspect) side.

The meniscus may be altered from traumatic injuries or due to age-related changes over time. Meniscal injuries are considered the second most common knee injury, with an incidence of 12% – 14% (61 cases / 100,000 people in U.S.). It is estimated that 10-20% of all orthopedic surgeries involve the knee meniscus (850,000 patients / year). Logerstedt 2010

Classification of meniscal damage is typically based on location and orientation of a tear. Mordecai 2014

Tears can be vertical longitudinal, vertical radial, horizontal, oblique, and complex. Mordecai 2014 A complete vertical tear has the potential to fold over within the joint space, creating what is known as a “bucket-handle” tear. Mordecai 2014 Typically a bucket-handle tear is considered “unstable”, and classically is thought to provoke mechanical symptoms such as “locking” of the joint. Previously, such symptoms were thought to warrant surgical intervention. Silhvonen 2016 However, recent evidence has emerged contradicting this usual practice, more on this later.

The underlying problematic theme for addressing this issue is the premise of a structural finding being directly causative of patient symptoms.

If you’ve been following our work, it should be apparent that things are becoming harder to label as “pathologies” or even as abnormalities based on radiologic imaging alone. The knee is no different. For example, meniscal damage and osteoarthritis are readily identifiable in asymptomatic populations (no reported pain and/or disability). Recently an article investigated the prevalence of “abnormal” imaging findings in 115 asymptomatic individuals (230 knees) using MRI. Some background data on the included cohort:

• 51 males, 64 females

• Median age: 44 years (ranged between 25 - 73 years of age)

• Based out of London

• Median Body Mass Index (BMI): 25 (ranged from 19.6 - 38.1 kg/m2)

• Physical activity (low intensity) was 2 hours / week (ranged from 0 - 4)

• Purposefully included sedentary individuals (not meeting activity guidelines)

The authors’ primary findings:

Nearly all knees (227/230; [97%]) of asymptomatic individuals showed abnormalities in at least one of the knee structures on MRI, of varying grades of severity. These findings included meniscal tears, cartilage abnormalities, bone marrow oedema and tendon and ligament abnormalities." Horga 2020

To further demonstrate these individuals were indeed asymptomatic and functional, the mean Knee Injury and Osteoarthritis Outcome Score (KOOS) for each item was 90/100. Specific to our discussion, the authors identified 30% prevalence of meniscal tears and 18% of meniscal degeneration in participants’ knees. A variety of tear types were identified - horizontal (23% knees), complex (3%), vertical (2%), radial (2%), and bucket handle tears (1%). Finally, 3% of knees demonstrated meniscal extrusion, a situation where the meniscal margin is extending beyond the tibial margin. The authors conclude:

Our study questions clinical decision-making regarding arthroscopy and its efficacy in reducing symptoms and treatment. The high rate of asymptomatic adults with knee joint abnormalities on MRI may indicate why arthroscopy and other surgical interventions for these do not result in better outcomes than sham surgery. For example, there is no evidence to suggest that meniscectomy benefits patients presenting with meniscal tear symptoms more than sham surgery does. Moreover, meniscectomy and other surgical interventions could lead to further complications or deterioration of the articular cartilage and increase the risk of osteoarthritis. Horga 2020

(For more, Not Your Image, references for the knee see Culvenor et al, Beals et al, Pappas et al, van der Heijden et al, and Guermazi et al).

With this in mind we will now discuss the current evidence regarding the best management of people dealing with knee pain being attributed to meniscal tears given that imaging has likely already been done, regardless of necessity.

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