An anterior cruciate ligament (ACL) injury frequently occurs among sports and physically active adults. Although the primary emphasis is frequently on restoring stability and resuming athletic activities, it is important to recognize a substantial long-term consequence: the heightened chance of developing knee osteoarthritis (OA). Let us explore this relationship and the measures you might use to alleviate the risks involved.
ACL Injuries and the Accelerated Path to OA
Osteoarthritis is a degenerative joint disorder marked by the degradation of cartilage, the smooth tissue that cushions the ends of bones in joints. A torn anterior cruciate ligament (ACL) significantly increases the likelihood of developing knee osteoarthritis, regardless of whether surgical reconstruction is performed. Within 15 to 20 years post-injury, approximately half of individuals with an ACL tear exhibit signs of osteoarthritis in the knee. This is particularly concerning as many ACL injuries occur in individuals under 30, potentially leading to osteoarthritis during their prime working years. Such injuries often affect teenagers and young adults, resulting in premature disability.
Why Does ACL Injury Lead to OA?
The precise mechanisms linking ACL injury to OA are complex and not fully understood, but several factors are thought to contribute:
- Initial Trauma: The force of the first injury might harm the cartilage and bone of the knee joint. ACL injuries frequently cause bone bruising, also known as hidden osteochondral lesions, which can lead to cartilage deterioration. The development of OA following ACL damage may be due to the initial injury to the subchondral bone and hyaline cartilage.
- Instability: A ruptured ACL causes aberrant knee mechanics and instability. This changed biomechanics can put more stress on the cartilage and other joint tissues, hastening their deterioration. ACL insufficiency impairs normal physiological knee bending, resulting in greater anterior tibial translation and internal tibial rotation. Under anterior and rotational loading, the posterior medial and lateral compartments experience greater mean contact stresses.
- Associated Injuries: ACL injuries often occur alongside other knee injuries, such as meniscal tears. Damage to the meniscus, which acts as a shock absorber in the knee, further destabilizes the joint and accelerates cartilage wear. The published frequency of knee OA following an isolated ACL tear is 13%. When meniscal injury is present with an ACL tear, this percentage increases to 21–48%.
Can OA be Prevented After an ACL Injury?
While an ACL injury increases the risk of OA, there are steps you can take to mitigate this risk:
- Rehabilitation: A comprehensive rehabilitation program is crucial to restore knee stability, strength, and function. Gait retraining should be incorporated into recovery.
- Address Associated Injuries: Prompt treatment of meniscal tears and other knee injuries can help minimize further damage.
- Maintain a Healthy Weight: Excess weight exerts additional stress on the knee joint, hastening cartilage deterioration.
- Low-Impact Exercise: Regular low-impact sports, such as swimming or cycling, can help preserve joint mobility and muscle strength without overworking the knees.
Conclusion
The correlation between knee osteoarthritis and ACL injuries is well-documented. Although an ACL injury increases the likelihood of developing OA, it does not ensure it. Recognizing the risk factors and taking early action to protect your knee will significantly reduce your chances of contracting this serious condition, allowing you to live an active and healthy lifestyle for many years.
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