ACL Sprain


An anterior cruciate ligament (ACL) sprain is a sprain to one of the main 4 ligaments of the knee. It is one of the most important ligaments of the knee and is used to provide stability of the knee joint. The anterior cruciate ligament (ACL) originates from the back of the femur (thigh bone) and attaches into the front of the tibia (shin bone). Its role is to prevent the forward movement of the tibia under the femur.
ACL injuries are one of the most feared injuries as they are the most common cause of prolonged absence from sport. They are very common in sports such as football, basketball, netball or skiing. They are also more common in females than they are in men. ThereĀ  are reasons why this may occur: the pelvic angle or the fact that women when jumping use more quadriceps activity than hip extensors when compared to men.

After an ACL repair athletes have a rehabilitation protocol lasting at least 9 months.

Most ACL tears occur when:

  • Landing from a jump.
  • Pivoting.
  • Decelerating suddenly.

The Anterior ligament sprains can be graded into three categories:

Grade 1 tear: A small number of fibres are torn resulting in some pain but allowing full function
Grade 2 tear: A significant number of fibres are torn with moderate loss of function.
Grade 3 tear: All fibres are ruptured resulting in knee instability and major loss of function. Often other structures are also injured such asĀ the meniscus (cartilage) or collateral ligaments. Surgery is often indicated.


Signs and symptoms of an ACL sprain/tear:

  • An ACL sprain is normally extremely painful.
  • Often you will hear a crack or a pop when you tear your anterior cruciate ligament.
  • Associated with a lot of immediate swelling to the knee (haemarthrosis).
  • Restricted movement of the knee.
  • Instability of the knee.
  • Positive special tests diagnosed by a Doctor or Physiotherapist.


For a non surgical grade 1-2 ACL sprain rehabilitation will follow the typical sprain rehabilitation consisting of:

  • Management of pain and swelling.
  • Restoring movement to your knee as allowed.
  • Strengthening your knee.
  • Restoring proprioception and stability to your knee.
  • Sports specific rehabilitation.
  • Improving any faulty biomechanics contributing to your injury such as weak hips, collapsing knees or collapsing arches of your feet.

In the case of requiring surgery a full rehabilitation program needs to be implimented to ensure a complete recovery. If there is time before your operation you need to begin prehabilitation to ensure your knee is as strong as possible before your operation.