The meniscus is a cushion in the knee that acts as a shock absorber. There are two meniscii in each knee.
They function in the same way that the plastic ring in a bicycle helmet works by distributing the force of a direct impact, and in so doing protect the joint cartilage and bone from injury and wear and tear. The meniscus also has a minor function in stabilizing the joint.
One can tear the meniscus in a traumatic event such as in a twisting injury while participating in sports. In the older individual, meniscal tears are usually degenerative in origin and are due to structural deterioration and wear and tear.
Unfortunately, the blood supply to the meniscus is poor and tears to the meniscus do not heal very well. Some tears have very little healing potential.
When one tears a meniscus, one may experience pain in that side of the knee and the knee may swell up.
In certain types of tears, the torn meniscus may also displace and get in the way of normal joint movement, thereby ‘locking-up’ the knee.
With a torn meniscus, the protective shock-absorption function is reduced and the knee joint is exposed to more damage, which may lead to early arthritis in the knee.
Small tears may be left alone with good resolution of the pain and swelling. A period of rest and physiotherapy will help in regaining the strength and function in the knee.
Should the symptoms persist, or should the tear be big or lock-up the knee, surgery may be indicated. This is usually in the form of a meniscus repair, or a partial meniscectomy, which involves resecting the damaged part of the meniscus.
Not all meniscal tears are repairable. Simple tears have a higher chance of healing after a repair. Healing rates for complex tears may be as low as 0-5%. A meniscal repair usually involves stitching the torn fragments together in a keyhole operation.
Tears located nearer the front of the knee may be repaired through small incisions around the knee. After surgery, it is important to protect the repaired fragments from too much strain and movement in order to allow the torn segment to heal.
One may require a few weeks in a brace and on crutches, after which a course of physiotherapy will help to regain the function in the knee.
Partial meniscectomy involves removing the torn part of the meniscus and is usually performed for tears that have a very low chance of healing after a repair.
The remaining meniscus will thus be smaller and less functional than the original meniscus, which may lead to early arthritis.
Modern techniques are evolving to improve the success rates of meniscal repairs. These techniques now give patients a better chance of preserving the meniscus and its shock-absorption function, and in so doing prevent the onset of early knee osteoarthritis.
In severe cases where the meniscus is completely damaged or missing and the patient has significant pain, other surgical procedures may be of help. These include bony realignment operations to off-load the part of the knee which has the deficient meniscus, or meniscus transplants.
During meniscus transplant surgery, a human meniscus from a deceased donor is transplanted into the knee to replace the missing meniscus. This operation carries significant risk with an average success rate. The transplanted meniscus may also wear out with time. It is important for patients to have a comprehensive assessment and discussion to determine if they are indeed a candidate for transplant surgery.
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