Can You Tear the Same ACL Twice? Risks & Prevention

The anterior cruciate ligament (ACL) is a strong band of tissue in the knee connecting the thighbone (femur) to the shinbone (tibia). It prevents the shinbone from sliding too far forward and limits excessive twisting, providing knee stability. For individuals who have experienced an ACL injury, re-injury is a common concern. It is possible to re-tear an ACL, whether the original ligament after non-surgical treatment or, more commonly, a reconstructed one.

The Reality of Re-Tearing

Re-tearing the same ACL can refer to several scenarios. This includes failure of the reconstructed graft itself, where the new tendon tears again. Graft failures can occur due to a new traumatic event, improper tunnel placement during surgery, or graft stretching. A re-injury could also mean a new tear to another part of the same knee, or an injury to the ACL in the opposite knee.

Re-tear rates for the reconstructed ACL range from 5% to 15%. However, considering injuries to either the reconstructed knee or the opposite knee, the overall re-injury rate can exceed 20% in some groups, especially young, active athletes. Research suggests almost 30% of young athletes returning to pivoting sports experience a second ACL injury within 24 months of their initial surgery and return to sport. These re-injuries often involve new trauma to the knee, but can also stem from technical issues during the initial surgery, such as misplaced tunnels for the graft, or problems with the graft’s biological integration.

Factors Influencing Re-Injury Risk

Several factors increase re-tear risk. Younger patients, especially those under 25, face higher rates, possibly due to higher activity levels and intense sports participation. Females also have a higher likelihood of re-tearing an ACL or tearing the opposite ACL compared to males, potentially linked to differences in anatomy, muscle strength, and hormones.

Returning to high-impact activities too soon after surgery increases re-injury risk. Many re-tears occur when individuals return to sport within nine months of ACL reconstruction, before the knee has fully healed and regained strength. Inadequate or incomplete rehabilitation also plays a significant role. Proper physical therapy is essential for restoring muscle strength, joint stability, and neuromuscular control, which involves the brain’s ability to coordinate movement and balance.

The type of graft used can influence re-tear rates. Allografts (donor tissues) are associated with higher re-tear rates, particularly in younger patients, compared to autografts (patient’s own tissue like patellar, hamstring, or quadriceps tendon). Other knee injuries, such as meniscal tears or damage to other ligaments, can complicate recovery and contribute to higher re-injury risk. Sports involving frequent cutting, pivoting, and sudden stops, like soccer, basketball, and skiing, inherently carry a greater risk of ACL injury.

Proactive Prevention Measures

Minimizing the risk of a second ACL tear requires a proactive approach. Adhering to the full rehabilitation protocol is important, even after the knee feels better, to ensure the reconstructed ligament and surrounding structures are strengthened for activity. Neuromuscular training is a key prevention strategy, focusing on improving balance, proprioception, and proper landing and cutting mechanics to help the body react effectively to movements that could strain the knee.

Targeted strength and conditioning exercises are beneficial. Strengthening the quadriceps, hamstrings, glutes, and core muscles provides greater support and stability to the knee. A balanced strength between the quadriceps and hamstrings is important, as imbalances can increase stress on the ACL. Implementing gradual return-to-sport protocols is important; rushing back to full competition too soon can increase re-injury risk. Many protocols suggest waiting at least 9 to 12 months after surgery before a full return to high-demand sports, allowing for graft healing and strength restoration.

Practicing proper movement patterns, such as landing softly from jumps with bent knees and keeping knees aligned over the feet, can reduce strain on the ACL. Avoiding awkward or “knock-kneed” landing positions is also important. Paying attention to the body’s signals, such as persistent pain or instability, can indicate potential issues and warrant medical consultation before pushing activity levels further.

Managing a Subsequent ACL Tear

If an ACL re-tear occurs, revision ACL surgery, a second procedure to reconstruct the ligament, is often considered. This surgery can be more complex than the primary reconstruction, as it may involve addressing issues from the first surgery, such as bone tunnel enlargement, and may require different graft choices. The surgeon will conduct a thorough evaluation to determine the most appropriate approach, which might include using a different type of graft or performing additional procedures to stabilize the knee.

For less active individuals or if surgery is not medically advisable, non-surgical management might be considered. This approach focuses on extensive rehabilitation to maximize knee function and activity modification to avoid instability. Recovery from a revision surgery is often longer and more challenging than the first ACL reconstruction. Beyond the physical aspects, experiencing a second ACL tear has an emotional impact. Acknowledging this and seeking support is an important part of the recovery process, helping individuals maintain resilience throughout rehabilitation.