Lateral Meniscus Tear

Inside the knee joint, apart from the articular cartilages that cover the articulating bone surfaces, there are also small pads of fibrocartilagenous tissue that act as a cushion between the two articulation bones.These are called menisci, and are two in number; on the inside is the medial meniscus and on the outside is the lateral meniscus.

The lateral meniscus is semi lunar in shape (as is the medial one). It’s concave on top and flat underneath (having a wedged cross section). Placed on the outer side of the upper surface of the shin bone, it forms a concavity on the almost flat articulating surface of the tibia (shin bone). This concavity holds the rounded articulating end of the femur (the thigh bone). This structural arrangement provides functional stability to the joint.

The meniscus acts as a cushion, taking up about one third of the impact load as the upper and lower leg bones make contact during joint movement. It disperses this load uniformly to the adjacent bone and thus prevents excess stress being concentrated at any one point.

Due to its location and function, the meniscus is subjected to a great amount of stress. When this stress exceeds the bearing capacity of the meniscus, injury occurs in the form of a small or large tear.

Cause:

The lateral meniscus is less frequently damaged than the medial meniscus. The tearing usually results from an abnormal/sudden twisting of the knee in the bent position, with the foot planted firmly on the ground.

In young people, especially athletes, the tearing is a result of a twisting injury or a direct trauma, while in the elderly the degenerative changes in the meniscal structure are usually responsible for the injury.

Symptoms:

• Pain and swelling are the most common complaints.
• Pain starts gradually and involves the outer side of the knee.
• In case of trauma, pain may be immediate and bleeding may lead to sudden swelling. Otherwise, swelling develops over a day or two as a result of accumulation of inflammatory fluid.
• Pain intensifies on bending or rotating the knee.
• The knee hurts while rolling over in bed at night (Cooper’s sign)
• Tenderness around the front or back of the knee when pressure is applied
• Cracking or popping sounds
• Locking of the joint when a torn piece catches in between the two articulating bone ends, causing severe pain.

Diagnosis:

The history indicates the injury, as well as a positive McMurray’s test. In this test the knee is hyper-flexed and, placing one hand on the inner side of the knee with the other holding the foot, the lower leg is rotated internally while extending the knee. Pain or a popping sound on extension indicates a torn lateral meniscus. This test mostly helps to detect tearing in the posterior part of the lateral meniscus. Arthroscopy and MRI give a conclusive diagnosis.

Treatment:

Non-surgical treatment works best for a tear that is recent and small, present on the outer side of the meniscus where circulation is better. However, when the symptoms do not subside, or if the tear is large or detached, or if an athlete has to remain on the field, surgery may be a better solution.

Surgery is mostly performed through arthroscopy.

Repairing the torn meniscus:

A longitudinal tear is repairable, while a horizontal or oblique tear generally isn’t. A tear present near the outer edge repairs well, as the blood supply is good.

Partial or Complete Menisectomy:

Where repair is not possible, the torn part of the meniscus is removed. It is better to preserve as much of the meniscus as possible, because otherwise the joint deteriorates more rapidly.

Rehabilitation:

After surgery, the knee is supported through a hinged brace and/or crutches. Rehabilitation focuses on improving movement at the joint, keeping it pain free, and strengthening the leg muscles to delay joint deterioration

The period of rest after the operation varies according to the intensity of the injury. Nevertheless, once pain and swelling have subsided, rehabilitation should commence.

Mobility exercises:

First start with static contractions and light stretching/bending.

Flex and extend the knee to the pain-free limit. In the early stages, support the knee using a band or towel wrapped around the foot.

Improve the range of motion gradually; perform the flexion in a standing position, against gravity. And later on, placing your foot on a stool, bend forward, flexing the knee to its full range.

Stretching the leg muscles:

Stretch to the pain-free limit; hold the stretch for a few seconds. Repeat.

Strengthening exercises:

Work on your quadriceps and hamstrings. Strong leg muscles decrease the load on the joint, which now lacks the normal cushioning provided by the meniscus. This allows for better healing of a repaired meniscus or in its absence (partial or complete menisectomy) delays further deterioration of the joint.

Start with mild exercises and then progress to more difficult level.

Care must be taken to avoid over-exertion and stressing the healing wound.

Provided the movement is comfortable you can start cycling and swimming as well.