What is a Meniscus Tear?
A meniscus tear is one of the most common knee injuries. The medial meniscus sits between the thigh bone and the shin bone on the inner side of the knee, while the lateral meniscus sits sits on the outside of the knee. The medial and lateral meniscus are made of a tough, rubbery cartilage that is designed to absorb impact and assist with fluid motion within the knee joint. With no menisci, the femur and tibia would rub together and then coating cartilage layer on the ends of these bones would quickly wear away.
Dr. Cunningham is a knee specialist at Vail Summit Orthopaedics. He is an expert at diagnosing and treating meniscus tears for patients in Vail, Summit County, Aspen, and Denver, CO.
How Do Meniscus Tears Happen?
Meniscus tears are typically seen in two age groups: younger adults engaging in cutting or pivoting sports, and older adults as a result of “wear and tear” on the meniscus.
In young adults, meniscus tears can occur when there is a sudden change of direction while running. The sheer force caused by the sudden directional change–usually with the foot planted away from the new direction–can tear the tough, rubbery meniscus. In young adults, isolated meniscus tears are uncommon. Usually, there is also an associated ligament tear in the knee, such as an ACL tear.
In older adults, meniscus tears usually occur with minimal trauma. Often patients report simply squatting down or quickly changing directions while walking and experiencing a pop and pain in the knee. As we age, the tough rubbery cartilage normally decreases in thickness and loses strength. “Degenerative” meniscus tears occur as a result of “wear and tear” changes in the structure of the meniscus which cause it to weaken and fray over time, predisposing it to ultimately tearing with minimal trauma. Patients that are above ideal body weight, or those who have done a lot of physical labor, or those who have done a lot of squatting and lifting are more prone to tear their meniscus.
What is the Difference Between a Medial and Lateral Meniscus?
There are similarities and differences between the medial and lateral meniscus. They are both crescent shaped and positioned in the joint space between the femur and tibia. They both have similar thickness on the outer edges, and then become thinner along their inner surfaces.
Located on the inside of the knee, the medial meniscus is subject to a higher risk of injury due to its positioning and the increased stresses it sees. The lateral meniscus sits on the outside of the knee. It has more mobility than the medial meniscus. The outer edges of the menisci are attached to the top of the tibia by thickenings of the joint capsule. The inner edges of the meniscus are not attached to bone. This facilitates necessary mechanical change to the menisci as the joint moves and functions. There is blood flow to the outer edges of both menisci, but no blood flow to the inner sections. Due to the limited blood supply, there is poor healing potential when tears occur along the inner portion of the meniscus, which is wear most older adults tear.
What Does a Torn Meniscus Feel Like?
The symptoms of a torn meniscus can vary depending if the tear is an acute tear occurring in a young person or a degenerative tear occurring in an older person.
With an acute injury and resultant meniscus tear in a younger patient there is typically:
- A sudden, severe injury often with feeling a pop in the knee
- Immediate and severe pain
- Swelling and stiffness of the knee
- Weakness and limited range of motion
- A sensation of catching or locking in the knee during knee movement
- Often other associated ligament tears causing knee instability and further pain
In contrast, with a degenerative meniscus tear in an older patient there is typically:
- Minimal trauma but often a pop or catch felt in the knee
- Minor to moderate pain
- Minimal swelling
- Pain when squatting or stair climbing or changing directions when walking
- Difficulty straightening and bending the knee fully
- Knee joint locking or catching
A meniscus tear is an injury requiring orthopedic attention, particularly in young adults with acute tears.
How is a Torn Meniscus Diagnosed?
The diagnosis of a torn meniscus begins with a thorough patient history and physical examination by an orthopedic knee specialist. The details of any injury–if known–will help inform the diagnosis. Tenderness over the meniscus at the joint line suggests a tear. A provocative test called a McMurray test can further indicate a torn meniscus.
An xray and MRI is usually required to confirm the diagnosis. An X-ray is used to rule out any arthritis or abnormalities to the bones of the knee joint. An magnetic resonance imaging (MRI) of the knee can provide information about the soft tissue of the knee joint. The knee joint coating cartilage, tendons, meniscus, and muscle can be evaluated for any fraying or partial or complete tears. An MRI can also help determine the presence of other abnormalities within the knee joint.
Does a Torn Meniscus Require Surgery?
Not all patients with a meniscus tear require surgery. In older adults who have a degenerative meniscus tear, but who are minimally symptomatic, surgery is not recommended. Older adults with moderate to severe knee arthritis often have associated degenerative meniscus tears. In these patients, the arthritis is typically the main source of pain, not the meniscus tear. Given this, surgery is not typically recommended but rather non-surgical treatments can help control the pain and swelling due to the arthritis.
Nonsurgical treatments for a degenerative meniscus tear not needing surgery are:
- Resting the knee and limiting activities for a period of time
- A knee compression sleeve
- Ice therapy
- Anti-inflammatory medications
- Physical therapy for restoring full range of motion, strength, and knee biomechanics.
- Possibly injection therapy
Some older patients with degenerative tears, particularly those with large, displaced flaps of meniscus may come to an arthroscopic surgery even if there is also arthritis in the knee. In surgery, the torn flaps of meniscus that are catching are trimmed away. These flaps will not heal if they were sewn together as there is no blood supply to them. These meniscus flaps are also no longer serving as a shock absorber cartilage in the knee and are simply causing pain. These patients can expect to be fully recovered in 4-6 weeks from surgery.
Younger patients with acute meniscus tears are best treated surgically. Without surgery, the meniscus will not typically heal, and if a patient waits too long, the tear can progress, and the tissue then becomes more complexly torn until it is no longer amenable to repair and instead has to eventually be removed.
The outer third of the meniscus is called “the red zone.” This area has blood supply and the meniscus can heal if sutured together. The inner two thirds of the meniscus is called “the white zone.” This area has no blood supply and will not heal, even if sutured together. For tears in the red zone of the meniscus, Dr Cunningham always recommends meniscus repair, so that the entire meniscus can be preserved with no meniscus being removed. Removing a significant portion of the meniscus in a young person will predispose the patient to developing early arthritis in the knee.
Dr Cunningham performs meniscus repairs arthroscopically. Several small incisions are made around the knee and an arthroscope is introduced. Specialized instruments are used to place sutures across the meniscus in order to hold the tissue together so the meniscus can heal. Following surgery, patients go home the same day. They are placed in a knee brace and for most repairs, they are allowed to fully weight bear on the knee as long as the knee is held straight in a brace. When there no body weight being applied to the knee, the knee can be moved through a full range of motion. Patients are otherwise going to physical therapy. Full recovery following meniscus repair surgery can take 3 – 4 months. Dr. Cunningham is a knee specialist at Vail Summit Orthopaedics and Neurosurgery. He is an expert at diagnosing and treating meniscus tears for patients in Vail, Summit County, Aspen, and Denver, CO. Contact Dr. Cunningham today.