You ask me, I answer, comprehensive understanding of meniscus injury

Author: Yuan Feng, Chief Physician, Shanghai Sixth People's Hospital

Zhang Chengyuan, attending physician at Shanghai Sixth People's Hospital

Qiu Yongjia Chief Technician, Shanghai Sixth People's Hospital

Reviewer: Zhao Jinzhong, Chief Physician, Shanghai Sixth People's Hospital

Q1: What is the meniscus?

The meniscus is two fibrocartilaginous discs in the knee joint, located on the inner and outer sides of the tibial plateau. The edges are thicker and closely connected to the joint capsule, while the center is thinner and free. The blood supply of the meniscus comes from the branches of the internal and external knee arteries, but there is no blood supply to the central part. Therefore, except for the possibility of self-repair after damage to the edges, the rest of the meniscus cannot repair itself after rupture. A normal meniscus has the function of increasing the concavity of the tibial condyle and lining the internal and external condyles of the femur, which can increase the stability of the joint, disperse the load, absorb shock, and help lubricate the joint and reduce friction.

Figure 1 Copyright image, no permission to reprint

Q2: I have never been injured, so how could I have meniscus damage?

There are usually two situations in which meniscus injuries occur. One is caused by indirect violent trauma due to knee twisting, and the other is the result of long-term accumulated weight.

For young people, if they are engaged in certain special jobs, such as squatting frequently at work, it will cause wear and even tear of the meniscus. Some sports, such as people who do breaststroke for a long time, are prone to medial meniscus injuries. Of course, sometimes, inadvertent injuries to the knee joint can also affect the meniscus. Especially for middle-aged and elderly people, because the meniscus itself has degenerative changes and poor texture, injuries can occur inadvertently when squatting or going up and down stairs, and there is not necessarily an obvious history of trauma.

Q3: I experience knee pain after exercise and suspect that I have meniscus injury. What should I do?

Generally, for knee pain after exercise, if there is no obvious sprain or trauma, you can rest and avoid exercise. If you have not recovered within 1 week, it is recommended to go to the hospital for examination. For those who have obvious knee trauma, hear tearing sounds in the knee during exercise, or have obvious knee swelling after trauma, it is recommended to go to the hospital immediately and take further treatment measures based on the examination results.

Q4: Why do we need arthroscopic surgery for meniscus injury?

The meniscus is a cushion that protects the joints. If it is damaged, it becomes a foreign body that damages the joints. You can imagine that there is a foreign body in the knee joint that constantly gets stuck in your joint. Every time you feel pain, your articular cartilage is being worn away. To put it in another way, it's like a stone stuck in a gear, and the wear and tear will eventually become more and more serious. If the meniscus is damaged to the 3rd degree, or if a 1st or 2nd degree injury causes long-term pain, you can recover by removing the "stone" or grinding it flat through arthroscopic surgery. If a meniscus injury is not treated for a long time, it will cause irreversible sequelae such as wear of the articular cartilage.

Q5: Can meniscus injury be sutured?

To determine whether the meniscus can be sutured, we must first understand the blood supply of the meniscus, because not all meniscus injuries are suitable for suture. Based on the blood supply of the knee meniscus, the knee meniscus is divided into three zones on the horizontal plane [1]:

① Zone I: Red-red zone, 1-3 mm from the edge of the knee meniscus (synovial edge), blood supply comes from the inner, outer and middle branches of the knee artery, with rich blood supply, called the knee meniscus blood supply zone, with the potential for complete healing, this part of the injury can be sutured;

② Zone II: Red-white zone, 3 to 5 mm inside the red-red zone of the knee meniscus, located at the edge of the blood supply zone, supplied with blood by the terminal branches of the capillaries in the red-red zone of the knee meniscus, has the potential to heal, and suture may also be considered for injuries in this part;

③ Zone III: White-white zone, the inner part of the red-white zone of the knee meniscus. It is the non-vascularized area of ​​the knee meniscus, and its nutrition is completely supplied by synovial fluid. It is not recommended to suture this part of the injury.

Figure 2 Copyright image, no permission to reprint

MRI examination of the knee joint can determine whether the meniscus is damaged, and can also roughly see the location and area of ​​the meniscus tear. However, imaging examination is only an auxiliary diagnostic method, and arthroscopy is the gold standard for diagnosis.

Q6: Can meniscus injury be treated conservatively? Under what circumstances is surgery necessary?

Regarding this issue, there are several suggestions[1,2]:

(1) For acute injuries, if the knee joint has obvious or mild symptoms and MRI shows a 3rd degree meniscus injury signal, arthroscopic surgery is recommended as soon as possible.

(2) For acute injuries, the knee joint has obvious symptoms or mild symptoms, and MRI shows 1 or 2 degree meniscus injury signals. Conservative treatment is recommended first. A brace can be worn for at least 1 month. After 1 month, appropriate weight-bearing activities can be started, and activities should be restricted and exercise should be avoided for 3 months. If the patient recovers after 3 months, surgery is not required. If symptoms persist after 3 months, arthroscopic surgery can be performed.

(3) For pain without obvious causes or caused by chronic strain, with obvious or mild symptoms in the knee joint, MRI showing a grade 3 injury signal, and positive physical examination signs, arthroscopic surgery can be performed as soon as possible. For MRI showing a grade 1 or 2 meniscus injury signal, and symptoms persisting for more than 3 months, arthroscopic surgery can also be considered.

(4) If there are no positive signs on physical examination, even if MRI shows abnormal meniscus signals, conservative treatment can be given first and the patient can be observed afterwards.

It should be noted that for most 3rd degree meniscus injuries, the pain will not be obvious, especially for injuries to the posterior horn of the medial meniscus. There will be no obvious discomfort when walking on a flat surface, and discomfort will only occur when squatting or going up and down stairs. In this case, arthroscopic surgery is recommended.

Funded Projects:

1.Shanghai Xuhui District Science Popularization Innovation Project (xhkp-HM-2024009)

2. Shanghai Health Science Popularization Youth Talent Capacity Enhancement Project (JKKPYC-2024-B06)

3. "City Six-Lingang" Close-knit Health Consortium Science Popularization Project (JKLHT002)

References:

1.OZEKI N, SEIL R, KRYCH AJ, et al. Surgical treatment of complex meniscus tear and disease: State of the art[J]. J ISAKOS, 2021,6(1):35-45.

2. PETERSEN W, KARPINSKI K, BIERKE S, et al. A systematic review about long-term results after meniscus repair[J]. Arch Orthop Trauma Surg, 2022,142(5):835-844.