|Internal derangement is an old term that describes internal damage to the joint generally caused by trauma. It is a nonspecific term that usually must be further refined by history, physical exam, x-rays, and frequently MRI studies. |
The knee joint is the largest of weight bearing joint in the body. It is a hinge joint that connects the rounded, bony ends (condyles) of the thigh bone (femur) and the shin bone (tibia) and is bounded in front by the knee cap (patella). Various ligaments, muscles, and tendons help confine joint motion within safe limits while the menisci and cartilage cushion the joint against considerable forces that bear on the knee. Damage from injury or chronic overuse to any of these stabilizing and cushioning structures results in pain and may lead to joint instability.
With the popularity of jogging and skiing and the vulnerability of major sports figures to career-ending knee injury, terms of joint pathology have come into common usage and in many cases have supplanted the term internal derangement. Ligament tears are especially common. The knee has four major ligaments and each is vulnerable to injury: the anterior cruciate ligament (ACL), the medial collateral ligament (MCL) the posterior cruciate ligament (PCL) and the lateral collateral ligament (LCL). Each ligament restricts certain abnormal movement of the knee. Motion beyond the limits of the ligaments will produce damage manifested by a partial or complete tear. Cartilage damage is another common problem. The specialized cartilage cushion between the femur and tibia (meniscus) can be damaged in the same manner as the ligaments and may even be damaged at the same time. Articular cartilage is the smooth layer that covers the joint surfaces in the knee. Damage to the articular cartilage is referred to as chondromalacia. The most common example of chondromalacia is the cracking and popping (crepitus) that many people feel under their knee cap (See Meniscus Disorders; Patella Chondromalacia; Fracture, Patella; and Sprains and Strains, Knee).
Risk: The knee is especially susceptible to injury because it carries the body's weight and its stability depends on a complex of ligaments, tendons, muscle, and cartilage. Although the knee can withstand large vertical forces, it remains vulnerable to horizontal and twisting forces. The risk for knee injury increases with participation in sports such as football, skiing, soccer, and basketball. Injuries to the ligaments and menisci occur most often in a range of young to middle-aged adults. Children and adolescents are the more likely to experience damage to the bones rather than to the ligaments of the knee joint. Females are more vulnerable to patellar and lateral meniscus problems (Levy).
Incidence and Prevalence: Knee pain is reported by about 20% of adult Americans and accounts for nearly 3 million outpatient and emergency room visits in the US annually (Levy). Among workers, traumatic knee injury is the second most common occupational accident. The MCL is the ligament most commonly injured, but damage to the ACL is the most common source of chronic joint instability (Levy).
Source: Medical Disability Advisor