The anterior cruciate ligament, or ACL, along with the posterior cruciate ligament, or PCL, is vital to maintaining the stability of the knee joint. Because of the nature of forces at the knee, tears, or rupture, of the ACL are common while PCL tears are rare. ACL tears affect about 200,000 people annually in the U.S., and usually occur during a traumatic knee injury. These injuries occur during sports activities such as basketball, football, and alpine skiing and happen during landing from a jump, pivoting, or rapid deceleration. The injury typically presents with acute pain, swelling, and instability (often described as buckling or inability to bear weight). Patients with ACL rupture often report hearing or feeling a pop at the time of the injury.
Physical examination of a knee with a torn ACL often reveals hemarthrosis (blood in the joint) and positive clinical test results (Lachman or anterior drawer test – done with the patient sitting and the knee flexed to 90 degrees, pulling the lower leg forward will result in movement of the lower leg towards the examiner). However, examination is often limited by pain and swelling. MRI examination of the knee can confirm an ACL tear while often revealing additional injury such as meniscal or cartilage tears which can influence decision making regarding treatment.
About half of a patients with an ACL tear will develop osteoarthritis a decade after ACL injury, regardless of surgical or nonsurgical treatment. Clinical practice guidelines have been developed regarding recommendations for management of ACL rupture. Many guidelines recommend early surgical ACL reconstruction (typically within six weeks to three months), including the guideline from the Americal Academy of Orthopedic Surgeons, to reduce the risk of future meniscal tears and improve long-term function. ACL repair is usually performed once the knee has full range of motion and is not swollen. Although surgical reconstruction is often recommended for younger patients and those who intend to return to physically demanding sports, there is no high-quality data to support this recommendation. Many studies have shown no clinically important differences between long-term outcomes for those who underwent surgical ACL repair versus those who were treated conservatively with no surgery and physical therapy and rehabilitation. This includes the development of secondary knee injuries such as meniscal tears.
Those with an ACL rupture plus an additional knee injury, for example a meniscal tear, often have more severe symptoms, such as knee locking, and will require surgery. Also, studies have shown that among those with sport-related ACL injuries, about 65% eventually return to playing that sport again. Due to the high probability of development of osteoarthritis years later following an ACL injury, many people with ACL injuries eventually wind up with knee replacement years later, regardless of whether or not they underwent surgical ACL repair. And finally, studies have reported a 16.9% pooled incidence of a second ACL rupture, which may occur either in the surgically repaired knee or the opposite knee. Current data supports an exercise first, surgery later if needed management strategy which may allow a substantial proportion of patients to avoid surgery without affecting clinical outcomes.
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