Jerky movements, sudden starts and stops, as well as sideways running or hopping, can all lead to an ACL injury. Soccer, tennis, basketball players and skiers are most at risk of acquiring ACL injuries, especially females. The reason behind the higher incidence of ACL injuries in females is yet unclear; however, anatomical differences and hormonal influence are suspected to be factors.
How the injury occurs:
A direct impact such as an accident or a bad collision during contact sports may cause tearing of the ACL; however, the cause is most often suddenly slowing down and rotating the knee at the same time (to change direction), landing on a twisted or outward extended knee, knee hyper extension, etc.
- A popping sound may signal the ligament injury at the time of the incident.
- There is a sudden onset of moderate to severe pain on the back and outside of the knee
- The joint feels wavering and unstable
- Placing weight on the affected leg aggravates the pain
- Swelling develops soon thereafter and limits joint movement
An acute injury may convert to a chronic problem, referred to as Chronic ACL Deficiency. The knee joint is unsteady, as the ACL is unable to play its role in holding the leg bones together and controlling the movement at the joint. The knee gives way under load; this abnormal pattern of movement may damage adjacent joint structures such as the cartilage covering the joint ends of the bones, and may predispose to bone inflammation (osteoarthritis).
Several orthopaedic tests are used for definitive diagnosis such as the Lachman test, Anterior drawer test and Pivot shift test.
The Lachman test is considered the most reliable diagnostic test. With the patient lying supine on the table, the examiner pulls the lower leg anteriorly, keeping one hand on the thigh. This gives the relative anterior shift of the lower leg bone, which in the case of a damaged ACL is 2 mm or more.