ACL Injuries in Athletes: Causes, Diagnosis, and Your Treatment Options
How the ACL Gets Injured
The anterior cruciate ligament is one of two cruciate ligaments inside the knee joint, positioned diagonally to control forward tibial displacement and rotational stability. For athletes in cutting and pivoting sports — soccer, basketball, football, lacrosse, skiing — the ACL is under considerable load every time they change direction at speed.
Most ACL tears occur without contact. The common scenario involves a deceleration followed by a sudden directional change, a jump landing with the knee in valgus (caving inward), or a planted foot while the body rotates above it. In these moments, force on the ACL exceeds its tensile strength before surrounding muscles have time to respond. Contact-related ACL tears — from a direct blow to the knee — make up the remaining minority of injuries and often involve concurrent damage to other structures.
Several factors increase susceptibility: female sex (due to anatomic and neuromuscular differences), younger age with incomplete neuromuscular maturation, prior ACL or knee injury, muscle fatigue, and playing on synthetic turf surfaces with higher shoe-surface friction.
Recognizing an ACL Tear
Athletes who sustain an ACL tear often describe a sudden pop, either felt or audible, at the moment of injury. Pain is immediate and typically severe. Within two to four hours, swelling from a hemarthrosis (bleeding into the joint) causes the knee to appear visibly distended. Attempting to continue playing is difficult, and when weight is placed on the leg, the knee often feels unstable or threatening to buckle.
Not all ACL injuries present dramatically. Partial tears may produce more subtle swelling and a knee that feels functional in straight-line activity but unstable with cutting movements. If you have knee pain after a pivoting injury that is not rapidly improving, an evaluation is appropriate rather than attempting to push through the season.
On examination, a physician will perform specific tests — the Lachman test and the pivot shift — to assess ligamentous integrity. MRI confirms the diagnosis, grades the injury, and identifies associated injuries to the meniscus, collateral ligaments, and cartilage, which are present in a significant proportion of ACL tears.
Treatment: Surgery vs. Rehabilitation
The decision between ACL reconstruction and rehabilitation-based management is one of the most important in sports medicine, and it is not the same for every patient.
Reconstruction surgery involves removing the torn ligament and replacing it with a graft — typically the patient's own patellar tendon, hamstring tendons, or quadriceps tendon (autograft), or donor tissue (allograft). Surgery is generally recommended for athletes who wish to return to cutting and pivoting sports, patients with concurrent meniscus or ligament injuries requiring surgical repair, young patients with significant residual instability, and individuals whose knee gives way during daily activities.
Non-surgical rehabilitation is appropriate for a subset of patients: those with partial tears, individuals willing to modify their activity level away from pivoting sports, older recreational athletes, or those with medical conditions that increase surgical risk. Rehabilitation focuses on strengthening the quadriceps, hamstrings, hip abductors, and core to provide functional stability. Some patients — termed "copers" — can achieve adequate knee stability through muscle compensation alone.
Recovery from ACL reconstruction typically takes nine to twelve months, though high-quality rehabilitation is required throughout to reduce the risk of re-tear, which remains elevated for the first two years after surgery.
Returning to Sport Safely
Return to sport is a milestone that should be determined by objective criteria, not calendar date. Athletes who pass strength and functional testing at appropriate levels have significantly lower re-injury rates than those who return based on time alone. A sports medicine specialist or physical therapist familiar with return-to-sport protocols can guide this assessment.
If you've experienced a knee injury or are concerned about ACL instability, the specialists at Maryland Orthopedic Specialists can help. Call (301) 515-0900 or [schedule an appointment online](https://www.mdorthospecialists.com/contact).
