How can you tell if you tore your acl?

Exam and MRI: A good physical exam can indicate an ACL tear: firmly hold the thigh in place, and with the knee bent 90 degrees, firmly pull the lower leg forward. If the lower leg freely moves forward much more than the other without a firm endpoint, this may indicate an ACL tear. The same test in opposite direction would indicate PCL tear. It need not be painful. See a doctor for exam, you may need an mri.

Effusion post trauma: Quick intrarticular effusion post trauma are frequently acl tears see an orthopedist. For exam.

See below: Symptoms of an acute tear of the acl include swelling of the knee, severe pain, often bruising seen as black and blue marks on the knee and a knee that may feel unstable and will feel like it will give way. Right after the injury, it may be hard for a doctor to make the diagnosis because of the swelling. The physical exam after the swelling has gone down and usually an MRI will confirm.

A good exam then MRI: Although most people think a MRI is necessary to diagnose a torn acl, most knee specialists can tell from a couple of simple test that can be done. With a high suspicion, a MRI is often then ordered and used then to confirm the findings of the exam. My suggestion for you is to see a md who is well trained and experianced in acl's and even revision surgery. Get their opinion.