Anterior Cruciate Ligament (ACL) Injury

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Original Editors - Stephanie Geeurickx, Kevin Campion

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Search Strategy

Search engines: PubMed, Web of Knowledge
Key words: anterior cruciate ligament + injury/treatment/characteristics/management

Definition/Description

Injuries to the ACL are relatively common knee injuries amongst athletes. They can range from mild such as small tears to severe when the ligament is completely torn. Both contact and non contact injuries occur allthough most common are non contact tears and ruptures.

Clinically Relevant Anatomy

The knee is being stabilized by 4 ligaments:

• Anterior cruciate ligament (ACL)
• Posterior cruciate ligament (PCL)
• Medial collateral ligament
• Lateral collateral ligament

The role of the ACL is to prevent forward movement of the tibia from underneath the femur. It is less thick than the PCL and thus more likely to be injured.

The ligament has a proximal attachment in the fossa on the postero-medial aspect of the lateral condyle of the femur and terminates distally on the tibial plateau in front of and lateral to the anterior tibial spine. The ACL has a multiple bundle structure which allows it to be functional at all knee angles. Two main aspects can be distinguished:

• Anteromedial part which is tight in knee flexion and lax in knee extension. It attaches on the proximal aspect of the femoral attachment and inserts on the anteromedial portion of the tibial insertion.
• Posterolateral band which is lax in flexion and tight in extension and partly prevents hyperextension. The fibers attach to the posterolateral aspect of the tibial attachment.
  

Mechanisms of injury / Pathological process

Three major types of ACL injuries are distinguished:

• Direct contact
• Indirect contact
• Non contact

Most common are the non contact injuries caused by forces generated within the athlete’s body while most other sport injuries involve a transfer of energy from a source external to the athlete’s body. A cut-and-plant movement is the typical mechanism that causes the ACL to tear: sudden change of direction or speed with the foot firmly planted. A direct impact to the front of the tibia or stiff-legged landing are other frequently reported causes. 

Women are three times more prone to have the ACL injured then men. A wider pelvis requieres the femur to angle toward the knee, lesser muscle strength gives less support to the knee and hormonal variations may alter the laxity of ligaments.

Characteristics/Clinical Presentation

• ­ There may be an audible pop or crack at the time of injury
• ­ A feeling of initial instability, may be masked later by extensive swelling
• ­ A torn ACL is extremely painful, in particular immediately after sustaining the injury
• ­ Swelling of the knee, usually immediate and extensive, but can be minimal or delayed
• ­ Restricted movement, especially an inability to fully extension
• ­ Possible widespread mild tenderness
• ­ Tenderness at the medial side of the joint which may indicate cartilage injury
  

Differential Diagnosis

A torn ACL mostly does not occur isolated: over 50% of all ACL ruptures have associated meniscal injuries. If seen in combination with a medial meniscus tear and MCL injury, it is called O’Donohue’s triad. The same characteristics for an ACL injury can be found at knee dislocations and meniscal injuries. Other problems that have to be considered are patellar dislocation or fracture, and a femoral, tibial or fibular fracture. Differentiation can mostly be made based on a thorough anamnesis with particular attention for the mechanism at time of injury. An additional MRI scan can visualize the injury.

Diagnostic Procedures

• Lachman test
• Anterior drawer test
• Pivot shift 

Outcome Measures

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Examination

An organized, systematic physical examination is imperative when examining any joint. Immediately after the acute injury, the physical examination may be very limited due to apprehension and guarding by the patient.

While inspecting, the examiner should look for any gross effusion or bony abnormality. An immediate effusion indicates significant intra-articular trauma. According to Noyes et al, in the absence of bony trauma, an immediate effusion is believed to have a 72% correlation with an ACL injury of some degree. Bony abnormality may suggest an associated fracture of the tibial plateau.

Assessing the patient’s range of motion (ROM) should be carried out to look for lack of complete extension, secondary to a possible bucket-handle meniscus tear or associated loose fragment. Palpation of joint lines and collateral ligaments can rule out a possible associated meniscus tear or sprained ligaments.

Medical Management

Immediately after the trauma, the RICE principle should be applied.

Conservative treatment of isolated ACL tears (including physiotherapy and use of a knee brace) can have good outcome and may be indicated in patients:

• with partial tears and no instability symptoms
• with complete tears and no symptoms of knee instability during low-demand sports who are willing to give up high-demand sports
• who do light manual work or live sedentary lifestyles
• whose growth plates are still open (children)

Surgical treatment is usually advised in dealing with combined injuries and for patients who frequently participate in high demand sports activities. RICE and electrotherapy can be applied during several weeks ahead of the surgery in orde to reduce swelling and pain, to attempt full range of motion and to decrease joint effusion. This will help the patient to regain better motion and strentgh after the surgery.

Physical Therapy Management

Before surgery

Therapy pre-ops can encourage strengthening of the quadriceps and hamstrings. Range of motion exercises should be included if there is no pain involved.

After surgery

• Week 1

Regular icing and elevation are used to reduce swelling. The goal is full extension and 70 degrees of flexion by the end of the first week. The use of a knee brace and crutches are imperative.

Multidirectional mobilizations of the patella should be included for at least 8 weeks. Other mobilization exercises in the first 4 weeks are passive extension of the knee (no hyperextension) and passive and active mobilization towards flexion. Strenthening exercises for the calf muscle, hamstring and quadriceps (vastus medialis) can be performed.

• Week 3-4

The patient must trie to genuinely increase the stance phase in an attempt to walk with one crutch. With good hamstring/quadriceps control, the use of crutches can be reduced earlier.

• Week 5

The use of the knee brace is progessively reduced. (9-11) Passive mobilizations should normalize motility but flexion should not yet be thorough. 9 Tonification of hamstrings and quadriceps (vastus medialis) can start in close chain exercises. The exercises should be started on light intensity (50% of maximum force) and progressively increased to 60-70%. The closed chain exercises should be built from less responsible positions (bike, leg presses, step) to more congested starting positions (ex.squad). The progress of the exercise depends on pain, swelling and quadriceps control. Proprioception and coordination exercises can start if the general strength is good. This includes balance exercises on boards and toll.

• Week 10

Forward, backward and lateral dynamic movements can be included as well as isokinetic exercises.

• Month 3

After 3 months, patient can move on to functional exercises as running and jumping. As proprioceptive and coordination exercises become heavier, quicker changes in direction are possible. To stimulate coordination and control through afferent and efferent information processing, exercises should be enhanced by variation in visible input, surface stability (trampoline), speed of exercise performance, complexity of the task, resistance, one or two-legged performance, etc.

• Month 4-5

Final goal is to maximize endurance and strength of the knee stabilizers, optimize neuromuscular control with plyometric exercises and to add the sport-specific exercises. Acceleration and deceleration, variations in running and turning and cutting manoeuvers improve arthrokinetic reflexes to prevent new trauma during competition. 

Key Research

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Resources

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Clinical Bottom Line

In order to provide the injured athlete with the best care, physiotherapists should have elaborate knowledge of anatomy and functioning of the ACL.

Recent Related Research (from Pubmed)

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