Twisted your knee? Heard a pop? How to tell what you’ve injured and when to seek treatment
Orthopaedic specialists explain the differences between meniscus, ACL and MCL injuries, why early treatment matters, and whether knee braces and compression sleeves actually work.
(Photo: Pexels/Towfiqu Barbhuiya)
New: You can now listen to articles.
This audio is generated by an AI tool.
Read a summary of this article on FAST.
Get bite-sized news via a new
cards interface. Give it a try.
Click here to return to FAST
Tap here to return to FAST
FAST
Your knees are some of the most hardworking joints in your body. They don’t just support your weight, they also absorb the impact of every step you take, which according to studies, is about 2.5 to 2.8 times your body weight.
Every time you run, you’re subjecting your knees to six to eight times your body weight – with each leg bearing the load around 500 to 700 times for every mile (or 1.6km) you run.
Trouble is, you don’t make it easier on your knees. Weight gain is one of the most common ways you add to their load; for every additional kilogram gained, the pressure on the knees increases by around four times.
And that’s not including the punishing movements you put your knees through, like pivoting and making sudden changes in direction, common when playing sports – and increasingly experienced at CrossFit and Hyrox events, said Dr Francis Wong Keng Lin, an orthopaedic surgeon-scientist from Oxford Cartilage & Sports Centre.
You don’t have to be sporty to have heard of meniscus injuries, and tears in the ACL (short for anterior cruciate ligament) or MCL (short for medial collateral ligament). Neither does age play a part. “We see meniscus tears in everyone from young athletes to middle-aged active adults and even in elderly patients,” said Dr Wong.
WHAT IS THE ANATOMY OF THE KNEE?
Each knee has two menisci and four major stabilising ligaments, explained Adjunct Assistant Professor Wang Ming, a consultant with Division of Sports, Shoulder & Elbow Surgery at Alexandra Hospital and National University Hospital.
The two menisci are the shock absorbers, and they’re located on the inner side of the knee (medial meniscus) and the outer side (lateral meniscus), continued Adj Asst Prof Wang.
“These are crescent-shaped structures of specialised fibrocartilage that sit between the femur (thigh bone) and tibia (shin bone). Without healthy menisci, the forces transmitted through the knee become concentrated over a small area, increasing the risk of cartilage damage and osteoarthritis over time.”
But don’t confuse the meniscus with the kneecap, Adj Asst Prof Wang highlighted. Known medically as the patella, the kneecap is a small bone located at the front of the knee that acts as a pulley to straighten your knee. “In contrast, the menisci are located deep within the knee joint between the femur and tibia, and function primarily as shock absorbers and load distributors.”
You’ve probably heard about the ACL and MCL because they’re the most commonly injured. There are four ligaments in each knee, including the lateral collateral ligament (LCL) and posterior cruciate ligament (PCL). All four are rigid, supportive bands of collagen tissue that connect the femur to the tibia, and are the reasons your knee doesn’t twist, collapse or move in any unnatural direction.
“The ACL is located in the centre of the knee joint,” said Adj Asst Prof Wang. “Its primary function is to prevent excessive forward movement of the tibia, and control rotational movements during activities such as running, jumping and changing directions.”
The MCL, he said, is located along the inner side of the knee. “It helps to stabilise the knee against forces that push the knee inward, known as valgus stress, and plays an important role in maintaining side-to-side stability.”
The lesser-known LCL and PCL also provide stability to the knee, according to Cleveland Clinic. The LCL stabilises the outside knee, while the PCL crosses behind the ACL to form an “X” at the back of the joint.
HOW IS THE KNEE INJURED? WHICH PART IS THE MOST PRONE TO INJURY?
Between the menisci and ligaments, said Dr Wong, meniscus injuries are the most common. “This is because the meniscus acts as the knee’s shock absorber, and can be injured both acutely during sports and gradually through age-related wear and tear. It also serves a secondary function as a knee stabiliser when other structures such as ACL and MCL are injured or compromised.”
Acute meniscus tears sustained during sports are typically caused by “twisting mechanisms, particularly when the knee is flexed and the foot remains planted”, said Adj Asst Prof Wang. Signs of such tears, he said, include pain along the inner or outer joint line of the knee, and swelling over the next 24 to 48 hours. There may also be mechanical symptoms such as catching, locking or clicking of the knee.
The trouble with acute meniscus tears is, some patients may initially be able to continue their sporting activity before symptoms intensify – and end up worsening the condition, said Adj Asst Prof Wang.
Contrary to popular belief, said Adj Asst Prof Wang, most ACL injuries occur without direct contact. Instead, ACL injuries arise from actions such as sudden changes in direction, pivoting on a planted foot, rapid deceleration, or landing awkwardly from a jump. You’ll know that something is wrong, said Dr Wong, when you experience a “pop”, immediate swelling, and a feeling that the knee is unstable after a twisting knee injury.
Meanwhile, “degenerative meniscus tears usually present more gradually, with intermittent aching pain, stiffness, or swelling that develops over time”, said Adj Asst Prof Wang. “Symptoms are often aggravated by squatting, kneeling or prolonged walking.”
MCL injuries, on the other hand, usually occur when a force pushes the knee inward either through contact from another player or during a movement that causes the knee to excessively collapse inward, said Adj Asst Prof Wang. The MCL ends up getting overstretched or sprained, and creates pain and tenderness on the inner side of the knee, added Dr Wong.
The good news is, the MCL is one of the more forgiving structures, said Dr Wong, “and most MCL injuries heal without surgery”. “However, close attention and bracing might be needed in most cases to ensure it heals well without residual laxity”.
Sometimes, all three injuries can occur together, said Dr Wong. Termed the “unhappy triad”, it is “classically due to a valgus and rotation injury that can occur in pivoting sports”, he said. First, the ACL suffers a tear, leading to instability. An MCL tear follows due to that instability. The meniscus tries its best to be the stabiliser but when the force is too great, a meniscus tear occurs, explained Dr Wong. “This causes intense pain and instability, and the patient usually is unable to walk after the injury.”
ARE YOU LESS LIKELY TO INJURE YOUR KNEE IF YOU DON’T PLAY SPORTS?
The sports most frequently associated with injuries of the menisci and ligaments include soccer, basketball, netball, handball, rugby, martial arts, badminton, squash, tennis, and the increasingly popular pickleball, according to Adj Asst Prof Wang.
“These sports involve rapid acceleration and deceleration, cutting, pivoting, jumping, and sudden changes in direction – all of which increase stress on the knee ligaments and menisci.”
But you’re not entirely off the hook if you don’t play sports. Slipping on a wet floor, missing a step while descending the stairs, tripping and twisting the knee during a fall, and rapidly changing direction while carrying heavy objects are examples of daily activities that can derail your knees, said Adj Asst Prof Wang.
“Meniscus tears are particularly common in middle-aged and older adults, and may occur during relatively low-energy activities such as squatting, kneeling, rising from a chair, or turning while standing,” said Adj Asst Prof Wang. “In older individuals, age-related degeneration of the meniscus can make it more susceptible to tearing with minimal trauma.”
HOW DOES SEEKING TREATMENT EARLY HELP WITH BETTER RECOVERY?
Early diagnosis can prevent minor injuries from becoming severe, lead to better outcomes, and may help avoid surgery altogether, said Dr Wong.
“Often, we see patients who describe their clinical scenario where they might already have felt the symptoms of a partial ACL tear or subtle meniscus tear, and yet, persisted to continue in their sporting activities, leading to a full tear requiring surgery,” said Dr Wong. “Unfortunately, the knee usually wins the argument. These situations can be avoided if early diagnosis was made and early non-surgical intervention was provided.”
To prevent long-term complications, certain meniscus tears are best repaired early, continued Dr Wong. “Delayed treatment may result in tears becoming irreparable, requiring tissue removal instead. Similarly, untreated ACL injuries can lead to secondary meniscus and cartilage damage.”
See a doctor as soon as possible when you experience rapid swelling, an inability to bear weight, knee instability, locking or giving way and/or persistent pain that does not improve over several days, advised Dr Wong.
SYMPTOMS TO LOOK OUT FOR
- Meniscus tear: Pain with squatting and twisting as well as locking, catching or clicking sensations.
- ACL injury: Instability, giving way, swelling and inability to return to pivoting sports.
- MCL injury: Pain on the inner side of the knee and discomfort with side-to-side movements.
Collapse
Expand
WHY IS SURGERY NOT ALWAYS NEEDED? AND WHAT IS DONE TO “REPAIR” THE INJURIES?
Other than assessing your knee’s degree of instability and pain as well as your imaging results (which could be via X-ray or MRI), doctors also take into account your level of athletic function to determine if surgery is needed, said Dr Chia Zi Yang, a consultant from Singapore General Hospital’s Department of Orthopaedic Surgery.
“Patients who lead a sedentary lifestyle can be good candidates for conservative, non-surgical management,” said Dr Chia. “In these cases, the ligaments and menisci can scar down and regain just enough strength to serve these patients well in their daily activities.”
Surgeons often strive to preserve and restore normal knee function with minimal surgical trauma, said Dr Wong, which usually means using arthroscopic and minimally invasive techniques. “The philosophy today is preservation rather than removal,” he said.
For example, “the meniscus is repaired with sutures, and the procedure can usually be carried out entirely through keyhole incisions”, said Dr Chia. In some selected patients, added Dr Wong, the meniscus repair may be combined with platelet-rich plasma (PRP) or bone marrow aspirate concentrate (BMAC).
Both PRP and BMAC are regenerative therapies that use the body’s natural healing properties to promote tissue repair, and reduce pain and inflammation. The difference between PRP and BMAC lies in the source of the biological substances injected into the knee. In PRP, blood is drawn and its platelets and growth factors are concentrated; in BMAC, stem and regenerative cells are harvested from bone marrow, usually from the hip.
To further help preserve the meniscus, Dr Wong also uses arthroscopic matrix-based meniscus repair (AMMR) technique, “which combines conventional suturing with a collagen matrix scaffold placed arthroscopically”.
When it comes to the ACL, “surgery usually involves reconstructing the ligament as the residual tissue is often not robust enough to be repaired directly”, said Dr Chia. This means reconstructing the ACL using a tendon graft, which is typically taken from the patient’s hamstring or quadriceps tendon, said Dr Wong (see video above). Sometimes, a donor graft is used.
Most MCL injuries are treated without surgery, said Dr Wong, but if they are, the ligament is repaired or reconstructed using, again, minimally invasive techniques. “Most MCL injuries can be successfully treated with bracing and rehabilitation, avoiding surgery altogether,” he said, adding that PRP injections have also been used successfully to aid MCL injuries that are not healing well.
DO COMPRESSION SLEEVES AND PATELLAR BANDS HELP WITH INJURY PREVENTION AND REHAB?
There are many over-the-counter products that claim to minimise knee pain – and you may have even tried some of them. Find out what the doctors say about them:
KNEE COMPRESSION SLEEVE
This snug elastic knee band may reduce mild pain and swelling – and can be useful for acute injuries when combined with RICE (rest, ice, compress and elevate) treatment, said Dr Wong. But note that the sleeve provides little stabilisation, said Adj Asst Prof Wang, which is what your injured knee needs.
If you already feel better with just a compression sleeve, Dr Chia said it usually means your knee is quite stable to begin with. “This can be due to a number of reasons, including mild or partial tears, strong compensatory muscles, or low functional demand on the knee.”
PATTELA BRACE AND BAND
A patella brace is typically a compression sleeve with adjustable straps and a silicone buttress that helps guide the kneecap during movement.
On the other hand, a patella strap, also known as an infrapatellar strap, is worn just below the kneecap. “The strap alters the distribution of forces within the patellar tendon and may reduce tendon strain during physical activity,” said Adj Asst Prof Wang, which may relieve some pain during jumping and running.
However, both products are not meant for ACL, MCL or meniscus injuries – and do not protect you from those injuries, said both Dr Wong and Dr Chia.
KINESIOLOGY TAPE
It is an elastic therapeutic tape applied to the skin around the knee with the aim of improving proprioception, modifying pain perception, and facilitating muscle activation, said Adj Asst Prof Wang.
Taping your knee does not provide any structural support as it works mainly through tactile feedback, said Dr Chia. Dr Wong added that the tape “may provide temporary pain relief and proprioceptive feedback, although scientific evidence suggests only modest benefits”.
You may feel more confident to move your knee when you use the abovementioned products – and may even gain some pain relief – but “the improvements in joint position sense are relatively small”, said Adj Asst Prof Wang. The “improvements” also don’t “translate into meaningful reductions in the incidence of ligamentous or meniscal injuries”.
THE VERDICT
In summary, you’re better off not spending money on these products. “Current scientific evidence does not support the use of knee compression sleeves, patella braces, patella straps, or kinesiology tape as effective methods to prevent ACL, MCL or meniscus injuries in athletes,” said Adj Asst Prof Wang.
Instead, “the most effective protection comes from strong muscles, proper movement patterns and the timely treatment of injuries”, said Dr Wong. “My honest advice to patients is still this: the best brace for the knee is still a well-conditioned leg”, which he summed up as strength (build strong muscles), mobility (range of motion) and balance (dynamic control and body awareness).
Source: CNA/bk
RECOMMENDED
Get bite-sized news via a new
cards interface. Give it a try.
Click here to return to FAST
Tap here to return to FAST
FAST
About The Author
