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The meniscus is a C-shaped piece of cartilage that acts as a shock absorber between the femur (thigh bone) and tibia (shin bone) in the knee joint. Meniscal tears are a common knee injury, especially in athletes. They can occur due to acute trauma or degenerative changes in older individuals. Traumatic meniscal tears often happen when the knee is bent and twisted forcefully, such as during a tackle in football or a sudden pivot in tennis.
When a meniscal tear occurs, there are two main treatment options – non-surgical management with physical therapy and activity modification or surgical repair of the torn meniscus. The decision of whether to pursue surgical intervention depends on several factors including the type and location of tear, age of the patient, pre-existing arthritis, and desired activity level.
However, many patients opt for non-surgical treatment, especially if the tear is small or they wish to avoid surgery. A key question is – what is the long-term risk of developing osteoarthritis in the affected knee if a traumatic meniscal tear is treated non-operatively? This report will review the current medical literature to analyze the association between untreated meniscal tears and the development of knee osteoarthritis.
The medial and lateral menisci are two wedge-shaped pieces of fibrocartilage located between the femoral condyles and tibial plateau. They play a crucial role in load transmission, shock absorption, joint stability, proprioception, and lubrication/nutrition of the articular cartilage.
Meniscal tears can be classified based on the tear pattern:
– Longitudinal: Vertical tear along the length of the meniscus
– Radial: Vertical tear that begins at the inner margin and extends towards the capsule
– Horizontal: Parallel to the tibial plateau, splitting the meniscus into upper and lower pieces
– Complex: Combination of tear patterns
– Root: Tear at the meniscal attachment to the tibia
– Bucket handle: Longitudinal tear with the inner fragment displaced into the joint
Tears are also classified based on location:
– Anterior horn
– Body
– Posterior horn
The blood supply to the meniscus is limited to only the outer 10-30% in adults. Therefore, tears in the outer “red-red” zone have the best healing potential, while those in the inner “white-white” zone have limited capacity to heal spontaneously.
The incidence of acute meniscal tears is estimated at 61 per 100,000 persons. In the United States, there are approximately 850,000 meniscal surgeries performed annually. Males aged 21-30 years old have the highest rate of meniscal injuries.
In one study of 541 patients with meniscal tears, 49% were traumatic and 51% were degenerative. Longitudinal tears were the most common traumatic tear pattern. Medial meniscal tears are 2-3 times more frequent than lateral tears.
The menisci protect the articular cartilage from excessive contact stresses. Loss of meniscal tissue from tears or partial meniscectomy increases contact pressures in the knee and alters joint biomechanics. Over time, this leads to degeneration of the articular cartilage and development of osteoarthritis.
Numerous studies have demonstrated the association between meniscal damage and knee osteoarthritis:
– In a study of 294 knees with symptomatic osteoarthritis, 91% had a meniscal tear on MRI. The presence of a tear was associated with more severe cartilage damage.
– A study of 991 subjects found that meniscal damage on MRI increased the risk of developing radiographic osteoarthritis within 30 months by 6 times.
– The Framingham Study followed 1233 knees without osteoarthritis at baseline for over 8 years. 14% developed symptomatic osteoarthritis. Meniscal tears and meniscal extrusion on MRI were associated with a 2.7 and 2.5 times increased risk of incident osteoarthritis respectively.
– In 221 patients undergoing partial meniscectomy, osteoarthritic changes were seen in 48% at 8 year follow-up and 67% at 16 year follow-up.
However, the mere presence of a meniscal tear does not always lead to osteoarthritis. The risk depends on several factors:
– Larger tears are associated with a higher risk of osteoarthritis compared to smaller tears
– Radial and root tears significantly disrupt the ability of the meniscus to dissipate hoop stresses and result in greater cartilage degeneration compared to horizontal tears
– Medial meniscal tears lead to more rapid osteoarthritis progression compared to lateral tears
– Tears in younger patients may have a better long-term prognosis than those in older patients with pre-existing cartilage wear
– Meniscal extrusion (subluxation of the meniscus outside the joint margins) increases osteoarthritis risk and leads to more rapid progression
Non-surgical treatment options for meniscal tears include:
– Rest and activity modification
– Physical therapy to strengthen muscles around the knee
– Anti-inflammatory medications
– Injections (cortisone, hyaluronic acid, PRP)
The METEOR trial randomized 351 patients over age 45 with knee osteoarthritis and meniscal tears to either arthroscopic partial meniscectomy or physical therapy. There was no significant difference in pain or functional outcomes between the two groups at 6 and 12 months. This suggests that many patients with degenerative meniscal tears and osteoarthritis can be treated non-operatively.
However, for younger patients with acute traumatic tears, delaying surgery may increase the risk of osteoarthritis. One study looked at 120 patients with ACL tears, 45 of whom had a concurrent meniscal tear. The patients treated with early ACL reconstruction and meniscal repair had a lower rate of osteoarthritis (11%) compared to those treated with delayed surgery (34%) at 7.5 year follow-up.
The aim of surgical treatment is to preserve as much functional meniscal tissue as possible in order to prevent osteoarthritis. Repair of meniscal tears is preferred over meniscectomy, especially in younger patients.
Meniscal repair is most successful for longitudinal tears in the peripheral red-red or red-white zones. Radial tears extending to the avascular white-white zone have a lower healing rate. Complex and degenerative tears are not amenable to repair.
Partial meniscectomy involves selective removal of the unstable torn portions of the meniscus while preserving stable tissue. However, resection of more than 50% of the meniscal width significantly increases contact pressures. Even with partial meniscectomy, the risk of developing radiographic osteoarthritis is 3.6 times higher than in un-operated knees.
Meniscal allograft transplantation and scaffold implants are options for patients with prior total or subtotal meniscectomy to reduce pain and slow arthritic progression. However, these do not completely restore normal contact mechanics.
In summary, untreated meniscal tears are a significant risk factor for the development of knee osteoarthritis. The degree of risk depends on the type of tear, location, and patient age. Peripheral, longitudinal tears in young patients have a better prognosis than complex, radial tears in older patients.
Non-operative management is appropriate for many degenerative tears and small, stable tears. However, larger, unstable tears in young patients should be considered for early surgical repair to preserve meniscal function and minimize the risk of osteoarthritis. Unfortunately, many tears are not amenable to repair, and even with partial meniscectomy, the risk of osteoarthritis is still increased compared to knees without meniscal injury.
The key to preventing osteoarthritis after meniscal tears is early diagnosis and appropriate treatment tailored to the specific tear pattern and patient characteristics. Preserving meniscal tissue and function, whether through non-operative care or meniscal repair, can help delay or prevent the onset of disabling osteoarthritis. Patients should be counseled that knee osteoarthritis is still a possible long-term outcome even with optimal management.
©2025 Dr Frank McCormick All Rights Reserved.
©2025 Dr Frank McCormick All Rights Reserved.