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Anterior Cruciate Ligament (ACL) Injuries

What is the ACL?

The anterior cruciate ligament in the knee is a thick band of connective tissue that connects the femur (the thigh bone) to the tibia (the shin bone). It is the primary knee stabilizer. Injury to the ACL is common in pivoting sports and leads to instability and dissatisfaction.

What are the common ACL injuries?

ACL tears are one of the most common injuries of the knee in patients between the ages of 16 and 39. ACL injuries typically occur without contact during pivoting, cutting and jumping with the knee slightly flexed.

Sports are the most common cause of an ACL injury, but any adult can experience a traumatic ACL injury caused by repetitive stress on the knee, a direct hit to the knee, an auto accident, slip and fall, a fall off of a ladder or missing a step.

The injury may be a stretched ligament, a partial tear or a complete tear (also known as a rupture). Treatment options include both surgery and non-operative treatment (conservative approach).

There is a consensus that in highly active patients engaged in jumping, cutting and pivoting sports, early anatomical ACL reconstruction is recommended due to the high risk of secondary injury to the meniscus and cartilage. Alternatively, with delayed surgery, a period of progressive rehabilitation to resolve impairments and improve neuromuscular function is recommended.

New research reports new findings that an ACL injury causes changes in the brain that need to be targeted with rehabilitation. At CAO Sports Performance Center we optimize rehabilitation to prevent reinjury.

What other ligaments and structures are involved in ACL injuries?

The ACL is one of the many important structures in the knee, all of which keep the knee joint stable and functional. Alongside the ACL is the PCL (Posterior Cruciate Ligament), MCL (Medial Cruciate Ligament), and LCL (Lateral Cruciate Ligament), which all prevent the tibia from translating various directions, and the MPFL (Medial Patellofemoral Ligament), which prevents the patella from translating outside of the intercondylar groove. Another important structure is the meniscus, which provides an optimal surface for femorotibial translation, helps distribute axial load, and absorbs shock. The same forces that cause an injury to the ACL can also stress each of these structures, which can result in an injury to multiple at once.

How is an ACL injury diagnosed?

Oftentimes an ACL injury can be diagnosed with a physical exam, which would include assessing the mobility of the knee and performing a Lachman’s test. The lachman’s test involves assessing the end-feel when the tibia is pulled anteriorly, and how far the tibia exceeds past the femur. In a healthy knee, there should be a firm end-feel and minimal anterior tibial translation. In a knee with an injured ACL, there will be a “mushy” end-feel, and anterior tibial translation >2mm compared to the uninvolved knee.

Imaging may also be used to diagnose an ACL injury. MRI is most commonly utilized as it is able to show the extent of an ACL injury and signs of damage to other tissues in the knee, including the cartilage.

What to expect from rehabilitation?

Rehabilitation is begun immediately after arthroscopic ligament replacement. Recovery generally takes about nine months and involves 6-18 months of progressive rehabilitation before a player is cleared by the medical team who will perform Return To Support (RTS) testing to gauge the athlete’s readiness and risk of reinjury. The goals of rehabilitation are to improve functional performance and reduce the risk of a second ACL injury. Exercises are designed to

  • restore range of motion, especially full knee extension
  • increase muscle strength and endurance
  • improve neuromuscular function (agility, stability, balance, core strength, muscle building and power)
  • sport specific training

How is an ACL injury treated?

Treatment for an ACL injury can vary based on the extent of the injury and the individual’s lifestyle. Conservative management may be chosen if the ACL isn’t completely torn, or the individual’s lifestyle doesn’t involve intense straining forces at the knee. In this case, a brace would be utilized to provide stability while the knee is heavily strengthened in physical therapy. However, it is important to note that if a torn ACL is not repaired, the knee can develop chronic instability and early onset of osteoarthritis due to the tibia shifting frequently.

Surgical intervention may be chosen if the ACL is completely torn or the individual’s lifestyle requires the knee to handle planting, pivoting, and sports activity. There are several ways in which a surgeon conducts the repair, which the patient and surgeon both agree on. The ACL can be repaired by utilizing tissue from the individual’s patellar tendon, hamstring tendon, or quadriceps tendon, which would involve another incision to harvest tissue from these structures. Another option is an allograft, which involves utilizing tissue from a human cadaver.

There will be a protocol following surgery in order to protect the repair. During this time, it is important to attend physical therapy to be guided through an individualized program with a goal of maximizing strength within precautions and make an eventual return to full function.

Return to sport (RTS)

Even with appropriate surgery and rehabilitation there is still a high risk of reinjury. Studies report that up to 25% of athletes that return to sport suffer a second ACL injury, and 30% occur within the first 20 athletic exposures.

The decision to return an athlete back into competition has significant implications ranging from the safety of the athlete to performance factors. Return to sports is determined by the needs of each patient because of the high reinjury rate that occurs when returning to sports, the high incidence of osteoarthritis at follow-up and the effects on the long-term health of the knee and quality of life.

  • Generally, after primary arthroscopic ACL reconstruction 75% of patients return to sport in nine months. The American Orthopedic Society of Sports Medicine and Arthroscopy Association of North American reports that 65% of players can return to sport before nine months; and 66.4% started physical therapy one week post op with unrestricted activity at 6-9 months. The Major League Soccer Team Physicians and the NFL and NCAA football team physicians allow return to sports before nine months in up to 82% of cases. Functional performance testing is used in the decision making of return to sport.
  • Most patients who suffer a partial ACL tear and do not to have surgery will recover with rehabilitation within 3-6 months. These patients typically have less demanding physical activities and progressive physical therapy, and rehabilitation can restore function.

Center’s for Advanced Orthopaedics team of sports, rehabilitation and surgical professionals offer next level skilled performance training, athletic development training, surgical guidance, and rehabilitative care as part of a holistic care program to get you back to the sports you love better than ever.

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