6 Napier Road #02-10 Gleneagles Medical Centre
Singapore 258499


+65 64712674

Anterior Cruciate Ligament Sprain

Brief Outline of Anterior Cruciate Ligament Sprain

ACL Tear

The anterior cruciate ligament (ACL) is one of the four ligaments of the knee and it holds the knee together from the front. It is commonly injured in sports where there are a lot of direction changes and possible impacts. Football, lacrosse, and other fast moving games that require quick changes often result in ACL sprains. The most common mechanism for this injury is when the knee rotates while the foot is planted. Sharp pain at the time of the injury accompanied by swelling in the knee joint may be a sign of an ACL tear.

Anatomy and physiology

The anterior cruciate ligament extends obliquely upwards, laterally and backwards from theĀ anterior intercondylar area of the tibia to the medial surface of theĀ lateral femoral condyle. This ligament prevents posterior displacement of the femur on the tibia, and also helps check hyperextension of the knee. When the foot is planted ficing the tibia in place, and the knee is rotated forcefully, the stress can cause a tear in the ACL. This can range from minor tearing of a few fibres to a complete tear. It can also be torn as the result of a hard blow to the knee; usually other ligaments and the meniscus are involved as well.

Knee Structure

Cause of ACL Sprain

Forceful twisting of the knee when the foot is planted. Occasionally a forceful blow to the knee, especially if the foot is fixed as well.

Signs and symptoms

Pain immediately that may go away. Swelling in the knee joint. Instability in the knee, especially with the tibia.

Complications if left unattended

If left unattended, this injury may not heal properly. The instability in the joint could lead to injury to other ligaments. Chronic pain and instability could lead to future limitations.

Medial Collateral Sprain


  • Ice
  • Immobilisation
  • Seek medical attention

Rehabilitation and treatment

Once stability and strength return and pain subsides, gradual introduction of activities such as stationary biking can be undertaken. Range of motion and strengthening exercises are an important part of rehabilitation. Swimming and other non-weight bearing exercises may be used until the strength returns to normal. Strengthening the muscles of the quadriceps, hamstrings, and calves will help to protect the anterior cruciate ligament. Proper conditioning before beginning high impact activities will also provide protection.

Long-term prognosis

ACL sprains that involve a complete tear often require surgery to reattach the ligament. Minor sprains can often be healed completely without surgery. Return to full activity may be a prolonged process and some activities may be limited.

Joint Pain Tel