1 Farrer Park Station Road #13-18 Farrer Park Medical Centre Singapore 217562

Opening Hours : Mon – Fri : 8:30am to 5:30pm | Sat : 8:30am to 12:30pm
  Contact : +65 6908 6933 (Tel) +65 6443 4933 (Fax) +65 6535 8833 (For Emergency)

An anterior cruciate ligament (ACL) injury is one of the most common knee injuries among athletes who play high impact sports like soccer, basketball, skiing, and hockey.

During an ACL injury, the ACL is overstretched and may partially or completely tear. A “pop” in the knee may be heard or felt during an ACL injury. In most cases, the knee will become unstable, swelling will manifest, and bearing weight will become noticeably excruciating. ACL injuries can also occur if the knee joint is bent side to side, twisted, or bent backward. Missing a step on a staircase and falling off a ladder can also be likely causes. Just like most body parts, the ACL can also weaken with age. That being said, a tear becomes more likely in individuals over 40 years of age. Treatment options can range from noninvasive alternatives (rest and rehabilitation exercises) to invasive approaches like surgery. Course of treatment will depend mainly on the severity of the injury.


Majority of ACL injuries often occur during fitness and sports activities that put strain and stress on the knee:

  • Pivoting with the foot firmly planted
  • Landing incorrectly from a jump
  • Making sudden stops
  • Changing directions abruptly
  • Collisions or a direct blow to the knee

ACL injuries are more likely to occur in women than in their male counterparts engaged in the same sports. This can be attributed to the difference in landing techniques between men and women athletes.

Also, it is observed that many women athletes have a strength imbalance in the thighs. Quadriceps are often more stronger than the hamstrings. The latter prevents the shinbone from moving forward too far—overextending the ACL in the process.

People who have had an ACL injury have a higher risk of developing knee osteoarthritis. The condition occurs when the smooth surface of the joint cartilage roughens and eventually deteriorates.


  • “Popping” sound at the time of injury
  • Pain especially when there is weight on the injured leg
  • Swelling knee within the first few hours of the injury
  • Limited knee movement due to swelling and pain


During physical examination, the doctor will look out for tenderness and swelling in the knee and will do a comparison between the injured and healthy knee. Patients will be asked to move the knee in various positions to assess overall joint function and range of motion.

While the diagnosis can be done based on the physical examination alone, other tests might be recommended to determine injury severity and rule out other possible causes.

Recommended tests may include:

Ultrasound – This procedure makes use of sound waves to visualize internal structures. Ultrasound is often done to check for injuries in the muscles, tendons, and ligaments of the knee.

Magnetic Resonance Imaging or MRI – An MRI device employs a strong magnetic field and radio waves to create images of the soft and hard tissues. An MRI can show signs of possible damage in the tissues of the knee as well as the extent of the damage caused by the ACL injury.

X-rays – In most cases, X-rays are prescribed in order to rule out bone fracture.


ACL injuries are best prevented by strengthening and stretching the leg muscles especially the quadriceps and the hamstrings (the front and back thigh muscles respectively).

Other ways to prevent ACL injuries include:

  • Not wearing shoes with cleats especially when engaged in contact sports.
  • Not wearing high-heeled shoes especially for very long periods.
  • Avoiding sports that entail a lot of contact and twisting.


Treatment for ACL injuries will depend on some of the following factors:

  • The ACL condition before the injury—this means partial tears, prior injuries, and changes secondary to age will be taken into consideration.
  • The overall condition and health of the knee before the injury took place.
  • The severity of injury or damage to the ACL. Injuries can be classified as grade l, ll, or lll sprains

First-aid care can be done to help alleviate pain and reduce swelling especially immediately after the injury.

The R.I.C.E. model of self-care is considered ideal.

Rest – Resting is needed for healing and it helps limit weight bearing on the knee.

Ice – Icing the affected knee for 20 minutes every 2 hours is recommended.

Compression – A compression wrap or an elastic bandage should be wrapped around the knee affected.

Elevation – Lying down with the knee propped up on the pillows is considered beneficial.


Treatment approach for ACL injuries will often commence with weeks of rehabilitative therapy. A physical therapist would recommend exercises that can be done at home or with continued supervision.

Using crutches and wearing a brace to help stabilize the knee might also be prescribed.

The main goals of rehabilitation include restoring the knee’s full motion range, strengthening the muscles, and reducing swelling and pain.

This course of treatment is often found effective in treating patients who are engaged in only moderate recreational activities and exercises, those who are relatively inactive, and those that are engaged in sports that do not put much strain on the knees.


Surgery might be the recommended course of treatment if:

  • More than one cartilage or ligament is injured
  • You’re an athlete who wants to continue doing sports that may involve pivoting, jumping, or cutting
  • You are young and active
  • The injury causes the knee to buckle while doing everyday activities

During ACL reconstruction, the damaged ligament is removed and replaced with a segment of tendon. This procedure is called a graft. A tendon from another part of the knee or from a deceased donor will be used. The graft will work as scaffolding where new ligament tissues can grow.

In most cases, successful ACL reconstruction coupled with rigorous rehabilitation can effectively restore knee function and stability. Athletes often resume playing sports after 8 to 12 months.

However, without treatment, the ACL would be unable to control knee movements, and the bones may rub against each other. The abnormal movement might cause tissue damage in the knee joints which may lead to osteoarthritis. It is advisable to see an orthopaedic surgeon  as soon as you notice the symptoms so treatment can be provided before the condition escalates.