What is an Anterior Cruciate Ligament Injury?
The Anterior Cruciate Ligament (ACL) is a very important stabiliser of the knee joint. Ligaments connect bone to bone, providing stability. An ACL injury results when this important ligament is damaged. It is the most commonly injured ligament in the knee.
What can cause it?
The classically described injury mechanism involves an indirect valgus (knee bent inwards) force coupled with a twist of the knee.
What are the symptoms and signs?
In the acute stage pain is a factor, however, this rapidly settles and the main symptoms are a feeling of instability or loss of confidence in the knee following repeated episodes of giving way.
There is often an instantaneous swelling of the knee following the injury. There may even be an audible ‘pop’ or ‘click’ heard at the time.
Can the problem get worse?
In isolated anterior cruciate ligament ruptures the natural history is often quite difficult to predict.
Some patients’ symptoms do settle with a dedicated course of ACL rehabilitation physiotherapy, which is directed towards neuromuscular optimisation of the knee joint.
A recent Scandinavian cohort/observational study, published in the British Medical Journal, showed that a significant proportion of patients do settle with just physiotherapy alone.
In summary symptoms following an anterior cruciate ligament injury include:
- Popping sensation at the time of the injury
Once the acute swelling and bruising have settled, a thorough clinical examination is performed including the following special tests:
- Lachman’s test
- Anterior drawer +/- a pivot shift
Your knee surgeon Mr. Mann will also examine you to rule out or confirm the presence of any associated injury such as:
- Focal meniscal injury
- Osteochondral damage
- Medial collateral ligament injury
- Lateral collateral ligament injury
- Posterior cruciate injury
- Posterolateral corner injury
We recommend the PRICE regime:
Protection – minimise the risk of re-injury, for moderate to severe sprains, the use of crutches is recommended as well as the use of a knee brace
Rest – by avoiding walking on the knee while it remains painful and swollen (at least 48 hrs)
Ice – apply immediately or as soon as possible following the injury to minimise swelling (make sure ice is wrapped in a towel and you apply until area becomes numb, remove and discontinue the ice at this stage, continued application following numbing may result in tissue damage)
Compression – bandages and dressings help immobilise the injured knee, reducing pain and swelling
Elevation – of the knee to at least heart level to help minimise swelling and aid soft tissue healing
During the initial stages of this injury, it is often difficult to perform a meaningful clinical examination as the knee is too painful. Your surgeon will guide you according to the grade of your ligament injury.
Effective rehabilitation is critical to ensuring full recovery: resolution of painful symptoms, swelling and restoration of stability. It is also important as it will prevent the risk of chronic knee instability. Using an experienced physiotherapist can help with your recovery and rehabilitation.
The different stages of rehabilitation include:
Stage 1 – this involves resting, protecting the knee and reducing the swelling (week 1)
Stage 2 – this involves restoring the range of motion, strength, flexibility and most importantly proprioception exercises of the knee (week 2-3)
Stage 3 – at this stage return to activities that do not require twisting or turning, and commence pool based exercises
Stage 4 – return to activities that require sharp, sudden turns (cutting activities) such as tennis and football (weeks to months)
Operative intervention is often reserved for elite athletes or those with recurrent instability despite neuromuscular optimisation who have a complete rupture of their ACL. While there are no high-quality clinical studies which reveal an association between instability and the early onset of degenerative joint disease, in practical terms the association of chronic instability and the onset of early degenerative joint disease, does not appear to be an unreasonable one. Click here for more information on ACL reconstruction surgery.
The key specific complications are:
- functional failure
- structural failure/re-rupture
- the need for revision surgery
- fixation failure
- blood clots
Reconstruction can be performed with a hamstring or bone patella tendon bone graft which is harvested from the knee at the same time as the reconstruction. Other options are available. The exact type of reconstruction along with fixation methods and tunnel placements will form part of an evidence-based shared decision-making process in the office.