Medial Meniscus Syndrome
Medial meniscus injury is much more common that lateral meniscus injury. Differences in the anatomical attachments of the medial meniscus compared to the lateral mean that the medial meniscus becomes distorted during combined flexion and rotation movements in a manner not experienced on the lateral side.
Mechanism of Injury
Medial meniscal injuries are usually considered as either traumatic or degenerative. Whilst degenerate tears may present with a gradual history of increasing symptoms, traumatic injuries will usually occur as the knee is extended and rotated from a flexed position against resistance. This may occur as a single event during a sports or during a period of unaccustomed squatting such as laying flooring or playing with children. The most commonly injured area is the posterior horn located at the back of the knee.
The exact presentation of a medial meniscal injury will vary according to the extent of tearing. Symptoms of a meniscal tear include:
- Locking: The inability to extend the affected knee to the same extent as the unaffected knee. Locking is due to a mechanical block when the torn piece of meniscus becomes caught between the two bone (femur and tibia). Not only can this be painful, it can also limit range of motion of the knee.
- Pain: This is usually intermittent in nature and associated with activities such as stair climbing or running. Patients will often complain of an inability to fully squat. Often there is tenderness along the joint line of the affected knee.
- Swelling: In large peripheral tears the injury may be associated with a post-traumatic effusion (swelling or “water on the knee”). More commonly, the irritation caused by the damaged meniscus causes recurrent effusions associated with exacerbations of the symptoms. Swelling can be severe and may cause stretching of the tissue surrounding the knee. This can lead to stiffness and pain, particularly with attempted bending of the knee.
- Clicking: Patients will often complain of clicking in the knee when a meniscal tear is present. The clicking may be painful or nonpainful and often times the patient will be able to reproduce the sensation with certain motions or positions of the knee.
This is useful in the assessment of additional knee pathology such as osteoarthritis that may impact on the prognostic information given to the patient.
Indicated in rare cases when an MRI cannot be performed (presence of metal in the body that is not compatible with MRI).
This is the most useful investigation for cases where diagnostic doubt exists. It is highly sensitive and specific but it is important to remember that both false negatives and positives do occur. MRI is typically performed when surgery is being considered and non-operative measures have failed to relieve symptoms.
In the majority of cases, a trial of non-surgical management is appropriate for medial meniscal tears. This includes physical therapy, anti-inflammatories, ice, rest, and avoidance of aggravating activities. Cortisone injections may help decrease inflammation, pain, and swelling in the knee. Some patients find simple knee braces effective in relieve their discomfort.
For cases where symptoms of meniscal tear do not respond to non-surgical treatment, arthroscopic excision may be warranted. In this procedure, the damaged meniscus is trimmed using small instruments inserted through small incisions. Healthy meniscal tissue is left behind to reduce the likelihood of developing arthritis in the future. Typical recovery is from 2-6 weeks.
In certain, specific cases the meniscus may be able to be repaired. This is usually restricted to those cases where a fresh, peripheral tear is identified at arthroscopy in a young patient. The limited application for meniscal repair is due to the poor blood supply found within the meniscus. Recovery from meniscal repair is usually longer than that of meniscal incision and may involve periods of limited weight bearing.
Most the literature regarding prognosis following meniscal excision dates from the pre-arthroscopic era of total open meniscectomy. As such there is a commonly held perception that excision results in arthritis. This is overly pessimistic. Having a meniscal tear is a significant injury to the knee. Ongoing mechanical symptoms indicate ongoing damage to the chondral surfaces of the joint. If an arthroscopic excision is performed before extensive chondral injury has been sustained, many patients do not develop problematic osteoarthritis and will experience long term symptom relief.