Anatomy
Summary
The knee is a hinge-type synovial joint that plays a vital role in movement and stability, making it prone to a variety of injuries and conditions. The anterior cruciate ligament (ACL) is the most frequently injured knee ligament, often compromised due to awkward landings or abrupt changes in speed. To diagnose ACL tears, clinicians employ the anterior drawer test and the Lachman test. On the other hand, posterior cruciate ligament (PCL) injuries are commonly due to direct blows to the anterior tibia when the knee is flexed, as seen in dashboard injuries or contact sports. The posterior drawer test serves as the go-to diagnostic maneuver for PCL tears.
The medial collateral ligaments (MCL)) and lateral collateral ligament (LCL) also also subject to injury. A valgus stress test is used for detecting MCL tears, while a varus stress test is utilized for LCL tears. The McMurray test helps identify meniscal tears. A severe knee injury can result in an unhappy triad, involving simultaneous damage to the ACL, MCL, and meniscus. Overuse injuries are also common, and include conditions such as prepatellar bursitis ("carpenterÕs knee"), patellar tendonitis ("jumperÕs knee"), Osgood-Schlatter disease, and patellofemoral syndrome ("runnerÕs knee").
Lesson Outline
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FAQs
The knee joint is a hinge type synovial joint, located where the femur, tibia, and patella meet. It is the largest joint in the body, and primarily functions to allow movement of the leg, as well as providing stability when supporting the weight of the body. Structures like the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL) provide cutaneous stability. Menisci provide shock absorption and weight distribution.
The "unhappy triad" refers to the simultaneous injury of three key structures in the knee: the ACL, MCL, and meniscus. This combination is often seen in severe knee injuries, typically caused by a forceful twisting motion or a side blow to the knee. Such injuries often require surgical intervention and a lengthy recovery period to fully rehabilitate the joint.
The Lachman test is commonly used to diagnose ACL injuries. In this test, the the knee is flexed at 20-30 degrees and anterior force is applied to the proximal tibia. If the tibia moves too easily, it could indicate an ACL injury. The posterior drawer test is used to diagnose PCL tears. Here, the knee is bent to 90 degrees, and the tibia is pushed posteriorly. If the tibia is too lax, it may indicate a PCL tear.
Ligament tears in the knee, including those to the ACL, PCL, MCL, or LCL, often lead to knee instability. This may make the knee feel like itÕs going to give out during physical activity. Other symptoms include pain, swelling, reduced range of motion, and often a loud pop or snap during the injury. Over time, these tears can lead to wear and tear of the knee joint and eventually lead to osteoarthritis.
Prepatellar bursitis, also known as "carpenterÕs knee," involves inflammation of the bursa in front of the kneecap, often resulting from frequent kneeling. Patellar tendonitis, or "jumperÕs knee," is an overuse injury common in athletes who engage in frequent jumping, causing strain and inflammation in the patellar tendon. Osgood-Schlatter disease often affects adolescents and is characterized by a painful lump below the kneecap due to stress on the patellar tendon. Patellofemoral syndrome, often termed "runnerÕs knee," involves pain around the kneecap and is common in runners due to repetitive stress on the knee joint.
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