Anterior cruciate ligament injury

Ligament injury near the knee

Prevention is by neuromuscular training and core strengthening. Treatment recommendations depend on desired level of activity. While adults with a complete tear have a higher rate of later knee osteoarthritis, treatment strategy does not appear to change this risk. ACL tears can also occur in some animals, including dogs. The most common knee injury in dogs is ACL or CCL rupture.

When an individual has an ACL injury, they are likely to hear a "pop" in their knee followed by pain and swelling. They may also experience instability in the knee once they resume walking and other activities, as the ligament can no longer stabilize the knee joint and keep the tibia from sliding forward. Reduced range of motion of the knee and tenderness along the joint line are also common signs of an acute ACL injury. The pain and swelling may resolve on its own; however, the knee will remain unstable and returning to sport without treatment may result in further damage to the knee. Risk factors include female anatomy, specific sports, poor conditioning, fatigue, and playing on a turf field. Injuries to the ACL are common, 250,000 ACL injuries occur on an annual basis. This corresponds to a 1 in 3,000 chance of an individual sustaining an acl injury. Ligaments in the ACL or meniscus are usually torn with an external force being applied to the knee joint. Your acl can be torn without an external force being applied

Female athletes are two to eight times more likely to strain their ACL in sports that involve cutting and jumping as compared to men who play the same particular sports. NCAA data has found relative rates of injury per 1000 athlete exposures as follows:
Men's basketball 0.07, women's basketball 0.23
Men's lacrosse 0.12, women's lacrosse 0.17
Men's football 0.09, women's football 0.28
The highest rate of ACL injury in women occurred in gymnastics, with a rate of injury per 1000 athlete exposures of 0.33. Of the four sports with the highest ACL injury rates, three were women's – gymnastics, basketball and soccer. Differences between males and females identified as potential causes are the active muscular protection of the knee joint, differences in leg/pelvis alignment, and relative ligament laxity caused by differences in hormonal activity from estrogen and relaxin. Birth control pills also appear to decrease the risk of ACL injury.

Some studies have suggested that there are four neuromuscular imbalances that predispose women to higher incidence of ACL injury. Female athletes are more likely to jump and land with their knees relatively straight and collapsing in towards each other, while most of their bodyweight falls on a single foot and their upper body tilts to one side. Several theories have been described to further explain these imbalances. These include the ligament dominance, quadriceps dominance, leg dominance, and trunk dominance theories. The ligament dominance theory suggests that when females athletes land after a jump, their muscles do not sufficiently absorb the impact of the ground. As a result, the ligaments of the knee must absorb the force, leading to a higher risk of injury. Finally, trunk dominance suggests that males typically exhibit greater control of the trunk in performance situations as evidenced by greater activation of the internal oblique muscle.

Before puberty, there is no observed difference in frequency of ACL tears between the sexes. Changes in sex hormone levels, specifically elevated levels of estrogen and relaxin in females during the menstrual cycle, have been hypothesized as causing predisposition of ACL ruptures. This is because they may increase joint laxity and extensibility of the soft tissues surrounding the knee joint. Study results have shown that female collegiate athletes with concentration levels of relaxin that are greater than 6.0 pg/mL are at four times higher risk of an ACL tear than those with lower concentrations. Additionally, female pelvises widen during puberty through the influence of sex hormones. This wider pelvis requires the femur to angle toward the knees. This angle towards the knee is referred to as the Q angle. The average Q angle for men is 14 degrees and the average for women is 17 degrees. Steps can be taken to reduce this Q angle, such as using orthotics. The relatively wider female hip and widened Q angle may lead to an increased likelihood of ACL tears in women.

During puberty, sex hormones also affect the remodeled shape of soft tissues throughout the body. The tissue remodeling results in female ACLs that are smaller and will fail (i. e. tear) at lower loading forces, and differences in ligament and muscular stiffness between men and women. Women's knees are less stiff than men's during muscle activation. Force applied to a less stiff knee is more likely to result in ACL tears. In addition, the quadriceps femoris muscle is an antagonist to the ACL. According to a study undertaken on female athletes at the University of Michigan, 31% of female athletes recruited the quadriceps femoris muscle first as compared to 17% in males. Because of the elevated contraction of the quadriceps femoris muscle during physical activity, an increased strain is placed onto the ACL due to the "tibial translation anteriorly".

The knee joint is formed by three bones: the femur (thighbone), the tibia (shinbone), and the patella (kneecap). These bones are held together by ligaments, which are strong bands of tissue that keep the joint stable while an individual is walking, running, jumping, etc. There are two types of ligaments in the knee: the collateral ligaments and the cruciate ligaments. The collateral ligaments include the medial collateral ligament (along the inside of the knee) and the lateral or fibular collateral ligament (along the outside of the knee). These two ligaments function to limit sideways movement of the knee. In the anterior drawer test, the examiner flexes the knees to 90 degrees, sits on the person's feet, and gently pulls the tibia towards themself. The Lachman test is performed by placing one hand on the person's thigh and the other on the tibia and pulling the tibia forward. These tests are meant to test whether the ACL is intact and therefore able to limit the forward motion of the tibia. The Lachman test is recognized by most authorities as the most reliable and sensitive of the three. Technological innovations like stop action photography, force platforms, and programmable computers have propelled biomechanics into a key research area within the human sciences. Advances in motion capture, musculoskeletal modeling, and human simulation have deepened our understanding of the mechanical causes of musculoskeletal injuries and diseases. However, measuring force at joint, muscle, tendon, and articular surfaces, especially in the knee, is complex and relies heavily on intricate modeling of motion capture and medical imaging data. This complexity has limited the involvement of biomechanists in designing, implementing, and evaluating prophylactic training interventions and neuromuscular rehabilitation programs.

Though clinical examination in experienced hands can be accurate, the diagnosis is usually confirmed by magnetic resonance imaging, which provides images of the soft tissues like ligaments and cartilage around the knee. An x ray may be performed in addition to evaluate whether one of the bones in the knee joint was broken during the injury. MRI is particularly useful in cases of partial tear of the ACL. The anteromedial band is most commonly injured compared to the posterolateral band.

Another form of evaluation that may be used in case physical examination and MRI are inconclusive is laximetry testing (i. e. arthrometry and stress imaging), which involve applying a force to the leg and quantifying the resulting displacement of the knee. The GNRB arthrometer, for example, is a knee arthrometer that is considered more effective than the Lachman test.

An injury to a ligament is called a sprain. The American Academy of Orthopedic Surgeons defines ACL injury in terms of severity and classifies them as Grade 1, 2, or 3 sprains.

Interest in reducing non contact ACL injury has been intense. The International Olympic Committee, after a comprehensive review of preventive strategies, has stated that injury prevention programs have a measurable effect on reducing injuries. These programs are especially important in female athletes who bear higher incidence of ACL injury than male athletes, and also in children and adolescents who are at high risk for a second ACL tear. Researchers have found that female athletes often land with the knees relatively straight and collapsing inwards towards each other, with most of their bodyweight on a single foot and their upper body tilting to one side; these four factors put excessive strain on the ligaments on the knee and thus increase the likelihood of ACL tear. There is evidence that engaging in neuromuscular training (NMT), which focus on hamstring strengthening, balance, and overall stability to reduce risk of injury by enhancing movement patterns during high risk movements. Such programs are beneficial for all athletes, particularly adolescent female athletes. Injury prevention programs (IPPs), are reliable in reducing the risk factors of ACL inquiries, referring to dominance theories. The ligament dominance theory reduced peak knee abduction moment but should be more focused on prioritizing individualized, task specific exercises focusing on an athlete's risk profile. It is more beneficial than a generic program. There is an increase in hip and knee flexion angles, such as plyometrics and jump landing tasks, which reduces the risk of quadriceps dominance. However, there were no changes found for peak vGRF (vertical ground reaction force), which measures for "softer" landings. Unfortunately, there was no conclusive data on how IPPs reduces the risk associated with leg dominance theory.

Nonsurgical treatment for ACL rupture involves progressive, structured rehabilitation that aims to restore muscle strength, dynamic knee control and psychological confidence. A living systematic review with meta analysis, updated in 2022, showed on the basis of three randomised controlled trials that primary rehabilitation with optional surgical reconstruction produces outcomes similar to early surgical reconstruction. In some cases the ACL may heal without surgery during the rehabilitation process—the torn pieces re unite to form a functional ligament. The purpose of exercise treatment is to restore the normal functioning of the muscular and balance system around the knee. Research has demonstrated that by training the muscles around the knee appropriately through exercise treatment, the body can 'learn' to control the knee again, and despite extra movement inside the knee, the knee can feel strong and able to withstand force. Typically, this approach involves visiting a physical therapist or sports medicine professional soon after injury to oversee an intensive, structured program of exercises. Other treatments may be used initially, such as hands on therapies in order to reduce pain. The physiotherapist will act as a coach through rehabilitation, usually by setting goals for recovery and giving feedback on progress. Non surgical recovery typically takes three to six months, and depends on the extent of the original injury, pre existing fitness and commitment to the rehabilitation and sporting goals. Some patients may not be satisfied with the outcome of non surgical management, and opt for surgery later.

ACL reconstruction surgery involves replacing the torn ACL with a "graft," which is a tendon taken from another source. Grafts can be taken from the patellar tendon, hamstring tendon, quadriceps tendon from either the person undergoing the procedure ("autograft") or a cadaver ("allograft"). The graft serves as scaffolding upon which new ligament tissue will grow. The surgery is done with an arthroscope or tiny camera inserted inside the knee, with additional small incisions made around the knee to insert surgical instruments. This method is less invasive and is proven to result in less pain from surgery, less time in the hospital, and quicker recovery times than "open" surgery (in which a long incision is made down the front of the knee and the joint is opened and exposed). The American Academy of Orthopedic Surgeons has stated that there is moderate evidence to support the guideline that ACL reconstruction should occur within five months of injury in order to improve a person's function and protect the knee from further injury; however, additional studies need to be done to determine the best time for surgery and to better understand the effect of timing on clinical outcomes. However, delaying ACL reconstruction in pediatric and adolescent populations for more than 3 months has been shown to increase the risk or meniscus injuries significantly. There are over 100,000 ACL reconstruction surgeries per year in the United States. Over 95% of ACL reconstructions are performed in the outpatient setting. The most common procedures performed during ACL reconstruction are partial meniscectomy and chondroplasty. Asymmetry in the repaired knee is a possibility and has been found to have a large effect between limbs for peak vertical ground reaction force, peak knee extension moment, and loading rate during double limb landings, as well as mean knee extension moment and knee energy absorption during both double and single limb landings. Analysis of joint symmetry along with movement patterns should be a part of return to sports criteria. Tampa Scale of Kinesiophobia, and a question from the Knee injury and Osteoarthritis Outcome Score quality of life subscale. Results showed that nine athletes sustained a second ACL injury Athletes who experienced a second ACL injury had higher scores on the ACL RSI and on the risk appraisal questions of the ACL RSI, and they met RTS criteria sooner than athletes who did not sustain a second ACL injury. After reading, all second ACL injuries occurred in athletes who underwent primary ACL with hamstring tendon autografts.

Cruciate ligament rupture is a common orthopedic disorder in dogs. A study of insurance data showed the majority of the breeds with increased risk of cruciate ligament rupture were large or giant.