Medial Meniscus - Sarah and Bryn

Task – Medial Meniscus

The medial meniscus is a fibrocartilage band that spans the medial knee, and lies on the head of the tibia.
Its anterior end is attached to the anterior intercondyloid fossa of the tibia, in front of the anterior cruciate ligament.
Its posterior end is fixed to the posterior intercondyloid fossa of the tibia, between the attachments of the lateral meniscus and the posterior cruciate ligament.
The medial meniscus separates the tibia and femur and serves as a shock absorber, to increase the contact area between the bones, reducing the peak contact force experienced. It also reduces friction between the two bones to allow smooth movement in the knee

Meniscus tear

There are three types of tear to the meniscus that can occur and these lead to another three types.

Longitudinal tear - Bucket handle tear
Radial tear - Parrot beak tear
Horizontal tear - Flap tear

The medial meniscus has a rich supply to its periphery, a tear there healing fast and usually quite well. However a deeper tear may not heal as well.

The neuroanatomy of the meniscus is not well described. But it is believe to be enervated in a similar manner to the arteries, more on the periphery less deeper, these nerve endings are believed to play a role in sensory feedback and proprioception.

Mechanism of Injury
• The meniscus both medial and lateral are often torn by a twisting injury, common in sporting injuries, which involve twisting and bending of the knee.
• Can also be damaged in the elderly as it becomes weaker, and more likely to tear.

Investigation
• When taking a history these things should be noted:
o Tears sometime related to significant trauma, but not always.
o The injury often results from twisting or bending of a weight bearing knee in various degrees of flexion and extension.
o Pain is often intermittent and results from synovitis or abnormal motion of the unstable meniscus fragment.
o The pain is usually localised at the joint line.
o Patients can complain of: clicking, scratching, catching, locking, pinching or the sensation of giving way.
o Swelling usually occurs as a delayed symptom or may not occur at all. Immediate swelling indicates a tear in the peripheral vascular aspect.
o Degenerative tears often manifest with recurrent effusion due to synovitis.

Examination
• Associated findings such as a perimeniscal cyst or ligamentous laxity suggest a higher likelihood of a meniscus injury.
• Joint line tenderness – is an accurate clinical sign, found in 77 – 86% of cases of people with meniscus tears.
• The tenderness must be differentiated from a collateral ligament tear, this pain will extend above and below the joint line towards the ligament attachments.
• Effusion occurs in approx 50% of tears.
• Range of motion
o A mechanical block to motion or frank locking can occur with displaced tears.
o Restricted motion caused by pain or swelling is also common.
• Tests that can be performed are:
o The McMurray test: elicits pain: The medial meniscus is evaluated by extending the fully flexed knee with the foot/tibia internally rotated while a varus stress is applied.
o The Steinmann test: Tibial rotation is performed with the patient seated and the knee flexed 90º. Asymmetric pain is created with external rotation when testing the medial meniscus.
o The Apley test: This maneuver is performed with the patient prone and the knee flexed 90º. An axial load is applied through the heel as the lower leg is internally and externally rotated. This grinding maneuver is suggestive of meniscal pathology if pain is elicited at the medial or lateral joint.

Management
• Physical Therapy/medical management:
A home physical therapy program or simple rest with activity modification, ice, and nonsteroidal anti-inflammatory drugs (NSAIDs) is the non-operative management of possible meniscus tears. The physical therapy program goals are to minimize the effusion, normalize gait, normalize pain-free range of motion, prevent muscular atrophy, maintain proprioception, and maintain cardiovascular fitness. Choosing this course of treatment must include consideration of the patient's age, activity level, duration of symptoms, type of meniscus tear, and associated injuries such as ligamentous pathology. A trial of conservative treatment should be attempted in all but the most severe cases, such as a locked knee secondary to a displaced bucket-handle tear.’
• Surgical Intervention
If symptoms persist, if the patient cannot risk the delay of a potentially unsuccessful period of observation (eg, elite athletes), or in cases of a locked knee, surgical treatment is indicated.
The basic principle of meniscus surgery is to save the meniscus. Tears with a high probability of healing with surgical intervention are repaired. However, most tears are not repairable and resection must be restricted to only the dysfunctional portions, preserving as much normal meniscus as possible.
Surgical options include partial meniscectomy or meniscus repair (and in cases of previous total or subtotal meniscectomy, meniscus transplantation). Arthroscopy, a minimally invasive outpatient procedure with lower morbidity, improved visualization, faster rehabilitation, and better outcomes than open meniscal surgery, is now the standard of care.
Partial meniscectomy is the treatment of choice for tears in the avascular portion of the meniscus or complex tears that are not amenable to repair. Torn tissue is removed, and the remaining healthy meniscal tissue is contoured to a stable, balanced peripheral rim.
Meniscus repair is recommended for tears that occur in the vascular region (red zone or red-white zone), are longer than 1 cm, involve greater than 50% of the meniscal thickness, and are unstable to arthroscopic probing. A stable knee is important for successful meniscus repair and healing. Thus, associated ligamentous injuries must be addressed. The most commonly associated ligamentous disruption is complete tear of the ACL, which must be reconstructed to prevent recurrent meniscal tears. Fortunately, the increased blood and growth factors in the knee during meniscal repair combined with cruciate reconstruction significantly improves the outcome of the meniscal repair. In ACL-intact knees with isolated meniscal tears, healing rates are less than those in ACL-reconstructed knees, but they are higher than those in ACL-deficient knees.
The principles of repair include smoothing and abrading the torn edges and bordering synovium to promote bleeding and healing. Likewise, needle trephination of the meniscal body (poking holes to create vascular channels) can be performed.
Human allograft meniscal transplantation is a relatively new procedure but is being performed increasingly frequently. Specific indications and long-term results have not yet been clearly established. Meniscus transplantation requires further investigation to assess its efficacy in restoring normal meniscus function and preventing arthrosis.

Complications of Surgury:

Can be intraoperative or postoperative

Intraoperative
-anesthetic problems
-articular cartilage damage
-vessel or nerve injury
-instrument failure

Postoperative
-anesthetic concerns
-thrombophlebitis
-hemarthrosis
-infection
-stiffness
-persistent pain
-effusion
-synovitis

Prognosis
Healing of a medial meniscus tear is slow. If surgery is required and the meniscus is removed there is an increase risk of osteoarthritis in later life.

References
• http://www.emedicine.com/SPORTS/topic160.htm