Meniscus injuries are very common athletic injuries of the knee. The meniscus is a shock absorbing cartilage in the knee. It is a C-shaped cartilage that is located between the femur (the top portion of the knee) and the tibia (the bottom portion of the knee). The medial meniscus is located on the inner aspect of the knee and the lateral meniscus is located on the outer aspect of the knee. The role of the meniscus is to provide load transmission, joint stability, lubrication, and nutrition. When the forces on the meniscus exceed the capacity of the meniscus to deform, a tear occurs. This usually occurs with a twisting injury of the knee in younger patients. In older patients, these tears may be degenerative, meaning that they occur as a result of wear and tear over time, or may occur as a result of a minor event such as squatting or kneeling.
Normal Medial Meniscus
Arthroscopic Surgery for Meniscus Tears
Evaluation and Diagnosis
Most meniscus tears can be diagnosed based on history and physical examination. Examination typically reveals joint line tenderness where the examiner pushes along the meniscus resulting in tenderness. There may be swelling of the knee. X-rays are recommended to evaluate for other conditions including arthritic changes, which may have an impact on the result of treatment of meniscus tears. An MRI is also recommended to confirm the diagnosis and to fully evaluate the condition of the knee such as joint surface cartilage wear and other problems that may need t be addressed
MRI showing medial meniscus tear (arrow)
Not all meniscus tears require surgery, especially if they are not causing symptoms. Meniscus tears that are not symptomatic or tears in patients with arthritis may be treated nonoperatively. The tears generally do not heal, but may not cause symptoms. If the tear continues to cause pain, arthroscopic surgery is recommended.
The majority of meniscus tears do not heal on their own due to a poor blood supply. The majority of the meniscus obtains its nutrition from the joint fluid and only the outer 20-30% of the meniscus has a blood supply. Most tears of the meniscus occur in the portion of the meniscus that does not have a blood supply and therefore, arthroscopic surgery to remove the torn portion of the meniscus is how these tears are typically treated. Arthroscopic surgery to remove a part of the meniscus is called arthroscopic meniscectomy and it has an approximately 90% success rate.
Over time, the success rate diminishes following the surgery due to the impact of having less meniscus cartilage. Having less meniscus cartilage places greater stress on the joint surface cartilage in that compartment of the knee, eventually leading to arthritic changes. The size of the tear and amount of meniscus removed along with factors such as a person’s weight and knee alignment play a role in how fast the arthritic changes occur. Those patients with arthritis may improve with surgery, but they may not or may get worse depending on the severity of the arthritis.
Vertical tears in the portion of the meniscus that has a blood supply can be repaired thereby maintaining the meniscus and its shock-absorbing function. Meniscus repair is preferable for those tears that are amenable to repair and the results of arthroscopic meniscus repair are as high as 80-90%. The success rate of meniscus repair is improved when performed in conjunction with an ACL reconstruction due to the increased bleeding and release of growth factors and other cells that can aid healing. Younger patients have a better rate of healing than older patients.
Arthroscopic Surgery of the knee
Flap Tear of Medial Meniscus
Medial Meniscus following removal of flap tear
Degenerative Medial Meniscus Tear in a runner
Medial Meniscus after partial removal of a degenerative tear in a runner
Large Peripheral Medial Meniscus Tear
Front of repairable tear (black arrow) showing it is next to the joint capsule (red tissue) with a good blood supply
Repaired front portion of meniscus
Rehabilitation following arthroscopic partial meniscectomy typically involves a short period of decreased activity and protected weight bearing. Ice and compression are very important in the immediate postoperative period. Physical therapy is recommended to decrease swelling, regain range of motion, and regain strength and endurance. It typically takes a few weeks for younger patients to return to their previous activity level and sports. It takes longer for middle-aged or older patients to return to their previous activity levels based on the amount of arthritic change present in the knee.
Dr. Khalfayan’s Tip: It’s helpful to decrease swelling early. Patients can move their knee as tolerated and can perform gentle quadriceps strengthening immediately after surgery.
After a meniscus repair, partial weight bearing is allowed and a brace may be used. Squatting is restricted for the first 3-4 months depending the size of the tear. Return to sport following arthroscopic meniscus repair can take 3-4 months depending on the severity of the tear and the sport.
Dr. Khalfayan’s Tip: After a meniscus repair, it is important not to squat until cleared to do so by your physician as squatting places the highest amount of stress on the meniscus.