The fundamental reason for surgical treatment of ACL rupture is to stop symptomatic instability which can produce recurrent injury- especially meniscal tears. Not all patients with ACL rupture have this instability pattern especially if they modify their activites. Hence predicting instability and need for early surgery is important to understand both by the patient and healthcare professionals (GP, Physiotherapist and orthopaedic surgeon).

The patient:

ACL rupture can occur both with contact and noncontact injury and quite often the patient can hear a pop/snap at the time of injury

Usually the swelling occurs soon after the injury

A knee that has persistent swelling for more than a few weeks after an injury and ‘not feeling right’ requires formal assessment

ACL rupture/instability can often be associated with meniscal or articular cartilage injury that can affect long-term outcomes

The healthcare professional:

Predicting instability is based on careful history taking, clinical examination and understanding patient symptoms and activity levels.

Poor results from ACL reconstruction can often be due to presence of significant meniscal and chondral injuries from chronic instability.

Preinjury hours and type of sports participation, laxity measurements and age are good predictors of need for ACL reconstruction

Presence of a meniscal tear or chondral injury requiring repair techniques also shifts the decision to ACL reconstruction

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Reference
Fithian et al, Prospective trial of a treatment algorithm for the management of the anterior cruciate ligament-injured knee. Am J Sports Med. 2005 Mar;33(3):335-46