Sports injuries account for a high proportion of ACL rupture. Tears can result from a variety of mechanisms but tibial internal rotation and valgus/abduction (Pivot Shift) most important
ACL tears common in skiing, football and netball. There is a 6% 5 year incidence in professional soccer players , 4% of australian rules football and 2% of NFL footballers.
Typically the patient notices an audible pop, followed by haemarthrosis occurring two to three hours later.
PRIMARY SIGNS OF ACL TEAR
• non visualisation or
• clear loss of continuity of AMB
• Loss of contact with femoral attachment (bare wall sign)
• Avulsion fracture of tibial attachment
SECONDARY SIGNS
Primary signs carry a strong predictive values for ACL rupture, especially when coronal and axial images are also used. Secondary signs of anterior cruciate ligament rupture can be divided into three groups:
• 1) those that involve a bony injury: posterolateral tibial (micro)fracture, osteocondral fracture lateral femoral condyle, segond fracture, central slip semimembranosus avulsion
•, 2) those reflecting soft tissue injury eg abnormal angulation of the ACL
• 3) those that reflect anterior tibial translation. More than 1cm anterior migration of post tibial margin wrt posterior femoral margini>
An ACL rupture Report should include:
• Site of rupture
• Whether displaced anteriorly
• Whether any longitudinal tear (ramp lesion)
• State of posterolateral corner
• Size/position of footprint and diameter of ligament for ACL reconstruction
Some ACL's do not look frankly ruptured, but appear discontinuous, kinked or otherwise abnormal. Others demonstrate enlarged sheaths with fibres separated by fluid material. To differentai partial from complete tears, all imaging planes should be assessed first. If there is still doubt, signs of anterior tibial translation should be sought. If these are positive, a high grade tear is more likely. Even if negative, the presence of clinical instability points to a high grade (complete rather than partial) tear. ACL reconstruction is unlikely to be performed in the absence of clinical instability.
The aetiology and clinical significance of cruciate ganglia is uncertain. Many are like asymptomatic though some symptoms resolve following aspiration. Whether they are the result of mucoid degeneration or injury is also unresolved.
