Anterior Cruciate Ligament (ACL) Injury

Patient Information

The knee is the largest joint of the body consisting of 3 bones and an extensive network of ligaments and muscles

  • The 3 main bones are femur, tibia and patella
  • Movements of the knee Joint; FLEXION (bending) and EXTENSION (straightening) occur between the femur, [patella and tibia which are covered in articular cartilage which is extremely hard yet smooth designed to reduce friction
  • Ligaments of the knee:

              > Medial collateral l ligament (MCL)

              > Lateral Collateral Ligament (LCL)

              > Anterior Cruciate Ligament (ACL)

              > Posterior Cruciate Ligament (PCL)


How Injury can occur:

The three main types of ACL injury occur because of:

Direct contact

Indirect contact

Non contact

  • Most common are due to NON CONTACT injuries caused by forces generated within the body.
  • While most others occur due to a sudden change of direction or speed while the foot is placed firmly on the ground.

Women are at greater risk than men of this injury due to

wider pelvis

Greater Ligament laxity

Neuromuscular Factors



The treating Consultant/ Physician and Physiotherapist will best provide information on level of your injury.

Grade 1 Sprain (Minor Injury)

> The fibers of ligament are stretched but there is no tear

> There is little tenderness & swelling

> The knee does not feel unstable or give way during activity

Grade 2 Sprain (Moderate Injury)

> The fibers of the ligament are partially torn or incomplete tear with bleeding (hemorrhage)

> There is little tenderness

> Moderate swelling and some loss of function

> The joint may feel unstable or give out during activity

Grade 3 Sprain (Severe Injury)

> The fibers of the ligament are completely torn (ruptured)

> The ligament cannot control knee movements

> The knee wilI feel unstable or gives out at certain times


Injuries to ACL rarely occur in isolation. Some common associated injuries include:

  • Meniscal Lesions:

        Over 50% OF al I ruptures have associated meniscal injuries


Acute Stage

> Directly after injury regardless of whether surgery w ill take place, physiotherapy aims are to :

>  Regain range of movement

> Strength

> Proprioception (sense of body’s position in space )

> Stability

Some exercises that may be performed at this stage are:

> Static quads/ SLR

> Knee flexion (bending), dorsiflexion/ plantar flex ion, circumduction

>Knee flex ion (bending)/ Knee extension (straightening) in sitting.

> Patellar mobilization.

> Neuromuscular electrical stimulation (NMES). 

Before Surgery

> Rest, Ice, Compression , Elevation (RICE) & Electrotherapy can be applied. during several weeks prior to surgery in order to decrease swelling and pain.

> To attempt full ROM and to reduce joint effusion (excess fluid in or around the knee joint ).

> Therapy prior to surgery can also include strengthening of the quadriceps. (muscles at back of the thigh)  and hamstrings  (muscles at the front of the thigh).

After surgery 

Week l:

> Regular icing and elevation are used to decrease swelling.

> The goal is full extension and 70 degrees of flexion by the end of lst week (ideally).

> Use of knee brace and crutch.

> Other mobilization exercises in the first 4 weeks include passive extension of the knee.

> Active mobilization towards flexion.

> Strengthening exercises for the calf muscle , hamstrings and quadriceps. Week 3-4:

> Patient must try to increase the stance phase in an attempt to walk with l crutch.

> With good hamstring I quadriceps control the use of crutches can be reduced.

Week 3-4:

> Patient must try to increase the stance phase in an attempt to walk with l crutch.

> With good hamstring I quadriceps control the use of crutches can be reduced.

Week 5:

The use of knee brace is progressively decreased.

> Passive mobilization should be normalize mobility but flexion should not yet be through.

> Exercises should be started on light intensity (50% of maximum force) progressively increased to 60-70% of effort.

>  Exercises should be built up using for example bike , leg press ,step-completion of these depends on pain , swelling and quadriceps control

> Proprioception & coordination exercises on stair can be attempted, if the general strength is good

Week 10:

> Forward I backward and lateral dynamic ic movements can be included.

Month 3:

> After 3 months clients should   move onto functional exercises for example running and jumps.

Month 4-5:

> Final goal is to maximize endurance and strength of the knee stabilizer

> Acceleration (speeding up) and deceleration (slowing down I stopping) in running & turning