ACL Injuries

Knee brace

ACL Injuries

The ACL – Anterior Cruciate Ligament is an important stabilising structure in the knee and one commonly injured in the athlete; especially those involved in sports that require a fast change of direction or pivoting actions.

ACL Function:

  • Anterior tibial translation stability
  • 2° stabiliser to tibial rotation and valgus forces
  • Limits hyperextension

Injuries can be mild to severe and even career ending for some athletes.


  • 70% of ACL injuries occur with no contact – landing a jump, pivoting or rapid deceleration
  • 30% of ACL injuries occur with direct contact with another player
  • Women are 3 times more prone to ACL injury than men
  • The ACL is at risk playing sports that require fast ‘change of direction’

Mechanisms of an ACL tear

  • Hyperextension
  • Flexion and internal rotation
  • Recovery from falling backwards – skiing
  • Direct blow to the posterior proximal tibia or anterior blow to distal femur with foot fixed

An ACL tear may range from a small partial tear resulting in minimal pain, to a complete rupture of the ACL resulting in significant pain and disability, requiring comprehensive rehabilitation and potentially surgery.

Grades of Injury

An ACL tear can be graded as follows:

  • 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. With these injuries, other structures are also often injured, such as the menisci or collateral ligaments. Comprehensive rehabilitation is required to return to full sporting activity and often surgery is performed to reconstruct the ligament, and/or repair other structures.

It is possible to function in normal ADLs (average daily living) without a normal ACL, but high demand sports may prove difficult to return to pre injury level. Athletes are often faced with the decision to undergo surgery in order to return to their previous level of competition or sport for that matter at a lower level of competence. ACL injuries have been known to curtail many promising sporting careers.

Diagnosis of an ACL tear

A thorough subjective and objective examination from one of our experienced physiotherapists at our clinic is usually sufficient to diagnose and ACL tear.

There are four main features of the history that indicate ACL damage.

  • Mechanism of injury
  • Hearing/feeling a ‘pop’ or crack
  • Haemarthrosis within 2 hours – usually significant pain and swelling of the knee joint
  • Feeling of instability especially when changing direction

On clinical knee examination the following tests are performed to test ACL integrity:

  • Lachmans
  • Pivot shift
  • Anterior drawer

An MRI will often be done to confirm diagnosis and determine the extent of damage or involvement of other structures within the knee.

ACL injury treatment

The first line of treatment following injury to the ACL should be those of the RICED principle. Early review by a physiotherapist is important to reduce swelling, improve movement and minimise muscle wasting. Your physiotherapist will also check other structures involved and provide relevant management.


Physiotherapy is vitally important to hasten the healing process, ensure an optimal outcome and reduce the likelihood of future recurrence of ACL injury.

Physio treatment may comprise of:

  • Exercises to improve flexibility, strength, lower limb balance and control
  • Soft tissue massage
  • Joint mobilisation
  • Taping/bracing
  • Education & activity modification advice
  • Biomechanical and neuromuscular correction
  • A gradual return to running and sport program
  • Sport specific exercise and
  • Return to sport testing

Surgical or non-surgical treatment?

The optimal management of an ACL rupture if often debated – surgery or non-surgical. However there is excellent evidence that show an extensive rehabilitation is vital in either decision. This decision often depends on age, fitness level and exercise goals.

Injury prevention programs are required by all patients with ACL injury to prevent recurrence.

A review by an Orthopaedic Surgeon and decision on whether to follow surgical or non-surgical management is usually made based on a number of factors:

  • Age
  • Inability to heal or conservative management failed
  • Functionally unstable
  • Other structures at risk: Meniscal or other pathology, Osteoarthritic changes
  • Lifestyle factors (e.g. occupation fireman)
  • Sport requirements (desire to return to sports that require pivoting & jumping)

Surgery for an ACL tear

The best outcomes from reconstructive surgery have been shown to occur in people whose knees have had some time to stabilise and recover; time suggested may vary onwards of 3 weeks but generally less than 6 months.

ACL Reconstruction

Generally comprises of arthroscopic surgery to reconstruct or repair the ACL using a graft to replace the torn ligament to restore stability to the injured limb – usually the hamstring or patella tendon. Some surgeons may also use the allograft or synthetic grafts. The hamstring is graft of choice according to current literature.

In those patients who undergo surgical intervention, rehabilitation should commence from the time of injury, not from the time of surgery. This is essential to minimise swelling, improve range of movement and strength and ensure an optimal outcome following surgery.

Post Surgical ACL Rehabilitation

Post-operative ACL rehabilitation is one of the most important aspects of ACL reconstruction surgery. The most successful and quickest outcomes result from the guidance and supervision by an experienced physiotherapist.

Basic outcomes or timeframes:

  • 6-12 months rehab
  • Return to sport 9-12 months

Focus on:

  • Full knee motion, strength, power and endurance
  • Balance, proprioception and agility retraining
  • Specific sporting & functional needs

The PEP program (Prevent injury & Enhance Performance Program) and/or FIFA 11+ program has been shown to decrease both first time ACL injuries and further ACL injuries after reconstruction. These programs are highly specific – the importance of proper technique especially in landing jumps cannot be overestimated.

PEP/FIFA 11+ programs should be continued after return to sport/activity.

Credit: BDG physiotherapy for information & Peter Hogg APA titled Sports Physiotherapist.

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PEP program (Prevent injury & Enhance Performance Program)

Peter Hogg

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