What are the symptoms of anterior cruciate ligament injury i should be looking for?

Instability: The hallmark of an acl deficient knee is instability or giving way of the knee with higher level activities involving cutting, jumping, pivoting, etc. Some individuals may experience this with routine day to day activities. The initial injury is often described as feeling a "pop" in the knee and followed by development of considerable swelling and variable pain.

Instability: Pain, swelling, and mostly instability. Buckling or shifting of the knee, as if it is dislocating when you change directions. The knee can appear normal outwardly most of the time with normal activities.

Pain and instability: Pain and an unstable feeling especially with pivoting type activities may indicate an acl injury.