The meniscus is 2 C-shaped fibro-cartilage within the knee joint that is wedged in between the 2 bone ends of the knee joint. One is located on the inner aspect of the knee joint (medial meniscus) and the other is located on the outer aspect (lateral meniscus).
Its main role is to act as a shock absorber to cushion the impact on the cartilage lining the articulating surface of the bones. On top of that, the meniscus also serves to provide stability to the knee joint and aid to distribute the load evenly across the knee joint.
Injury to the meniscus occurs due to the huge amounts of compressive loads applied onto the knee joint or due to twisting or rotational forces across the knee joint. These compressive or twisting forces gets absorbed by the meniscus substance and can result in a tear.
Meniscus injury typically occurs in 2 main groups of patients: the young patients, who usually sustain an acute meniscus tear from a twisting injury during sports or a traumatic accident to the knee; and the middle to older age group patients, who typically develop a degenerative meniscus tear from repetitive compressive overload over a period of time, with minimal or no acute trauma precipitating the tear at all.
Patients with a traumatic meniscus tear will report sudden onset pain and swelling of the knee immediately after the injury.
The other symptoms patient complains of is ‘locking’, or a sensation that something is periodically stuck out of its place within the knee joint.
Lastly, some patients also notice an inability to extend or bend their knee fully as if something is trapped within and limiting the knee movement.
As mentioned, the young athletic individuals typically sustain a meniscus tear as a result of a twisting injury to the knee during a high impact or pivoting sport like soccer, basketball, netball, skiing.
These meniscal tears can also occur together with accompanying injuries, like an anterior cruciate ligament tear, in which case the patient may also experience the sensation of the knee giving way.
Older non-athletic individuals also can get a meniscus tear from a low impact injury or no trauma at all, largely as a result of the deteriorating quality of the ageing meniscus.
Middle to older individuals sometimes reports a pop sound and a sharp pain developing at the back of the knees without significant trauma to the knee.
This is typical of a degenerative meniscus posterior root tear that can have a significant consequence if left untreated.
In the examination of the knee with a torn meniscus, there will usually be tenderness along the knee joint, and with significant injuries, a notable swelling or effusion (fluid within the joint) in the knee can be present.
Special provocative tests to stress the torn meniscus will be performed to confirm the site of the meniscus tear.
Lastly, we will examine and assess the knee to look out for other associated injuries, like a ligament or cartilage injury.
An MRI scan is the standard imaging modality to confirm the diagnosis of a meniscus injury. This is a pain-free, non-invasive scan that has no radiation.
It is very sensitive to detect even small meniscus tears, and it also helps to evaluate the extent and severity of the meniscus tear and thereby allowing your doctor to decide if the tear can be left alone to heal on its own, or if it needs a surgical repair.
A significant proportion of degenerative meniscus tears, or tears that do not give rise to any symptoms, can be left alone without surgical intervention. Some of these smaller meniscus tears can also go on to heal on their own. The location of the tear also helps us decide on the healing potential of the tears, with peripheral tears more like to heal than central tears.
Traumatic sizeable tear, unstable vertical tears, meniscus tears associated with an ACL injury, and significant tears like a bucket handle tear will do better with arthroscopic surgical repairs.
More recently, there is growing evidence of accelerated joint degeneration as a result of untreated meniscus root tears, and we now recommend treating persistently symptomatic root tears with arthroscopic repair to prevent early onset arthritis in the middle age individual.
Almost all meniscus tears can be successfully treated using minimally invasive arthroscopic keyhole technique. This is essentially the use of 2 to 3 sub-centimetre skin incisions to introduce a camera (arthroscope) and minimally invasive instruments to perform the meniscus procedure under direct magnified vision from the camera.
The meniscus tear is either partially debrided (removal of the torn portion) or repaired with sutures. We generally try to preserve and hence repair meniscus tears as much as possible.
But not all meniscus tears will heal, and some patient will do better with partial or limited resection of the damaged meniscus.
The decision to repair or debride the tear will be dependent on many factors, including the age of the patient, the location and duration of the tear, the type of tear pattern, and the presence or absence of other joint injuries (eg. ACL tear). Your surgeon will have an in-depth discussion with you on the surgical plan prior to embarking on surgery.
The procedure is usually performed as day surgery and you can be discharged 2-4 hours post-procedure.
Depending on whether a debridement or repair is done, you will be allowed to put varying amounts of weight on the operated leg immediately after surgery. Range of motion exercises are typically started immediately after surgery, but once again the absolute range that is allowed will depend on the surgery performed.
Most patients will weight bear fully on their operated knee without much discomfort and regain good functional range of motion by 6 weeks after meniscus surgery.
Meniscus tears are very common knee injuries. With a proper diagnosis, treatment, and rehabilitation, patients often recover full and return to their pre-injury abilities.