Manual tests Most ACL injuries can be diagnosed by examining the knee and comparing it to the other, non-injured knee. When a doctor suspects ACL injury in a person who reports a popping sound in the knee followed by swelling, pain, and instability of the knee joint, they can perform several tests to evaluate the damage to the knee. These tests include the pivot-shift test,<unk>  drawer test, and Lachman test. The pivot-shift test involves flexing the knee while holding onto the ankle and slightly rotating the tibia inwards. In the<unk>  drawer test, the examiner flexes the knees to 90 degrees, sits on the person's feet, and gently pulls the tibia towards him or herself. 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. Medical imaging<unk><unk>  ligament tear seen on MRI. T1 left, right PDW. 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. It may also permit visualization of other structures which may have been coincidentally involved, such as the menisci or collateral ligaments. 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 perhaps the most used technique for diagnosing the state of the ACL, but it is not always the most reliable technique as the ACL can be obscured by blood that fills the joint after an injury. Arthrometers/Laximeters 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. These medical devices basically replicate manual tests but offer objective assessments. The GNRB arthrometer, for example, is a knee arthrometer that is considered more effective than the Lachman test. Classification 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. Grade 1 sprains occur when the ligament is stretched slightly but the stability of the knee joint is not affected. Grade 2 sprains occur when the ligament is stretched to the point that it becomes loose; this is also referred to as a partial tear. Grade 3 sprains occur when the ligament is completely torn into two pieces, and the knee joint is no longer stable. This is the most common type of ACL injury. Around half of ACL injuries occur in conjunction with injury to other structures in the knee, including the other ligaments, menisci, or cartilage on the surface of the bones. A specific pattern of injury called the "unhappy triad" (also known as the "terrible triad," or "O'Donoghue's triad") involves injury to the ACL, MCL, and medial meniscus, and occurs when a lateral force is applied to the knee while the foot is fixed on the ground.
Anterior cruciate ligament injury
Tibial plateau fracture
Posterior cruciate ligament injury
Knee dislocation  Knee dislocation  1
Medial knee injuries
Pes anserine bursitis
Patellar dislocation
Patellar subluxation syndrome