Grades of Injury
An ACL injury is classified as a grade I, II, or III sprain.[35]
Grade I Sprain
The fibers of the ligament are stretched, but there is no tear.
There is a little tenderness and swelling.
The knee does not feel unstable or give out during activity.
No increased laxity and there is a firm end feel.
Grade II Sprain
The fibers of the ligament are partially torn or incomplete tear with hemorrhage.
There is a little tenderness and moderate swelling with some loss of function.
The joint may feel unstable or give out during activity.
Increased anterior translation yet there is still a firm end point.
Painful and pain increase with Lachman's and anterior drawer stress tests.
Grade III Sprain
The fibers of the ligament are completely torn (ruptured); the ligament itself is torn completely into two parts.
There is tenderness, but limited pain, especially when compared to the seriousness of the injury.
There may be a little swelling or a lot of swelling.
The ligament cannot control knee movements. The knee feels unstable or gives out at certain times.
There is also rotational instability as indicated by a positive pivot shift test.
No end point is evident.
Haemarthrosis occurs within 1-2 hours.