Each knee has 2 C-shaped pieces of cartilage between the femur (thigh bone) and the tibia (leg bone), the medial and the lateral meniscus. The medial meniscus is on the inside and the lateral on the outside of the knee. The menisci look like potato wedges. The menisci act as shock absorbers and load sharers. They are the cushions of the knee joint. A torn meniscus is one of the most common knee injuries.
Meniscal tears can usually develop in one of 2 ways, traumatic in the young and degenerative in the old. In younger (<40 years) and active individuals, a torn meniscus can result from forceful twisting of the knee, such as a sudden “stop & turn”, or sudden pivoting of the knee. Essentially what happens is that you twist your bended knee while you put your weight on it. Certain sports increase the risk of this happening, such as tennis, squash, football and skiing.
In older people (>40 years), the menisci start to become weaker and more friable and can tear more easily, even without significant trauma. In fact, many of these occur spontaneously or with innocuous activities, such as kneeling or squatting while you do your house errands or your gardening.
People who get a traumatic meniscal injury may report a sudden onset sharp pain inside the knee accompanied by a crack or pop. It can take several hours for the knee to swell up and it is not uncommon for these people to keep going and the injury. Degenerative tears can be more insidious. Symptoms of a torn meniscus include:
• Sharp pain on the inside or outside of the knee, depending on the involved meniscus
• Pain on deep sitting or squatting, if the back part of the meniscus is involved
• Sometimes there can be a dull ache rather than sharp pain
• Painful clicking and catching or locking. If your knee is locking, you might have an unstable torn meniscus that needs more urgent medical attention
• Your knee may also feel like giving way
The doctor will take a history and perform a gentle physical exam. An x-ray is usually normal but might be necessary to quickly rule out other pathologies, such as fractures. The best test for a suspected meniscal tear is an MRI scan. This will provide high resolution images of the soft tissues of your knee and confirm the torn meniscus or other associated injuries that may occur, such as a torn ACL.
If you have an isolated torn meniscus and your symptoms are mild, you might opt for conservative management. This will involve rest, avoiding activities that aggravate your knee as well as physical therapy. If your pain is severe or getting worse and you don’t seem to improve with the above measures, you are likely to need a knee arthroscopy.
Knee arthroscopy involves putting a camera inside your knee through 2 or 3 small 5mm incisions and having a look around. This is a very common orthopaedic procedure, usually performed under general anaesthetic. It is a day procedure and patients can go home the very same day if they wish. During the procedure, the surgeon will visualize the structures of your knee, diagnose and address any pathology present. A torn meniscus may be treated arthroscopically either by debridement (trimming), or with a meniscal repair. Debridement involves trimming the meniscal tear to smooth edges. Debridement is usually the treatment modality of choice in older patients with old tears, complex tears, or tears of the inner third of the meniscus that have poor supply and are unlikely to heal. The other treatment modality is meniscal repair that involves the use of special arthroscopic devices that use tiny suture anchors loaded in small needles through which the surgeon can introduce and tie sutures in order to repair the torn meniscus (all-arthroscopic repair). Tears that are likely to be amenable to repair are the acute ones (the ones that happened recently), tears in patients < 40 years, vertical peripheral tears, horizontal tears, bucket handle tears that are caught early. It is important to know that meniscal has a poor blood supply. The outer third of the meniscus (red zone) had the best blood supply, whereas the inner third (white zone) has the worst. Surgeons often do this distinction by meniscal region and say that “red-red” will heal, “white-white” won’t heal and “white-white” might heal.
Whether your tear needs debridement or repair is often difficult to determine on MRI grounds only. This is instead typically a determination that is done intraoperatively, meaning that your surgeon will decide what is the right thing to do during the procedure.
Unfortunately, only a minority of torn menisci are amenable to repair (about 25%). However, the good news is that once repaired, your torn meniscus has a great chance to heal (about 90%). So, odds are that you will do well after meniscal repair.
Rehabilitation after meniscal repair is very important. You will typically protect the knee for the first 6 weeks and get it going thereafter with regular physiotherapy, will the intent to return to regular activities 3 months after surgery.
A situation that warrants special attention is the locked knee. A locked knee is a knee that won’t straighten. This kind of situation needs urgent medical attention, as a locked knee is commonly due to a displaced bucket handle tear. This condition needs an urgent MRI scan and likely knee arthroscopy sooner rather than later, as delays may be detrimental and lead to accelerated knee arthritis.
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