Final answer:
An ACL tear is the injury that includes instability of the knee with pain and swelling.
Step-by-step explanation:
The injury that includes instability of the knee with pain and swelling is C. ACL tear. An ACL tear refers to a tear or sprain of the anterior cruciate ligament, which is a major stabilizing ligament in the knee joint. When the ACL is injured, it can lead to knee instability, pain, and swelling.
Learn more about ACL tear