A relatively young person with knee arthritis, which is almost exclusively on one side of the knee, with severe pain and limited ambulatory tolerance, is a candidate for unicondylar knee replacement. When knee pain from osteoarthritis, interferes with daily activity, walking tolerance, and independence, it is time to consider this alternative. Patients may choose a unicondylar knee replacement when they have exhausted conservative measures and they cannot maintain normal activities of daily living.
A person with advanced knee arthritis and severe pain and limited ambulatory tolerance, is a candidate for total knee replacement. When knee pain from osteoarthritis, interferes with daily activity, walking tolerance, and independence, it is time to consider this alternative. Many individuals choose a total knee replacement so they can maintain normal activities of daily living.
The anterior cruciate ligament is the most commonly disrupted knee ligament tear in the knee. Our understanding of its role in knee stability, diagnosis of injury and surgical reconstruction have all advanced in recent years. the anatomy of the human knee is shown in the drawing. The collateral ligaments provide stability in a side to side plane. The anterior and posterior cruciates provide stability in a front to back plane. Additionally, these ligaments which are within the joint, provide a linkage system which guides the complex rolling-gliding motion of the knee. The menisci (cartilage) on both the inside and outside of the knee increase the contact area between the joint surfaces. In this way, they decrease the load in any one area of surface cartilage. A tear of the anterior cruciate is often associated with a meniscal or a collateral ligament tear. These injuries occur most often in athletics, but accidents or work injuries may also disrupt the cruciate if the mechanism of injury is similar. The injury may simply occur with a sudden change in direction while running, or with hypertension of the knee. Often an audible "pop" is heard or a sensation of "tearing" within the knee is felt. Within a few hours or a day, the knee swells and weight bearing may become difficult. If left untreated, many knees with this injury become unstable and are referred to as a "trick" knee. They may buckle unexpectedly, especially with rapid changes in direction.
The most common knee injury is related to the semilunar (meniscus) cartilage tear. There are two of these in each knee. One is medial (on the inside) and the other is lateral (on the outside) of the knee. Each appears like a crescent moon and is attached on its outer edge to the knee capsule and at each end to the tibia by ligament attachments. The meniscus is responsible for a four-fold increase in surface contact between the bones of the knee (tibia and femur). The meniscus also aids in shock absorption between the joint surfaces and aids in knee stability and lubrication. Complete loss of the meniscus is known to cause eventual arthritis. Each meniscus is made of cartilage. The outside one third has a blood supply and the capacity to heal. The inner two-thirds of the meniscus has more limited capacity to heal. A tear of the meniscus may occur following major trauma or none at all. This depends on the age of the individual and prior injury and activities. Not all tears are symptomatic, and many older patients are unaware they have a tear. Symptomatic tears are those which cause knee pain, locking, knee catching, clicking, stiffness, or recurrent swelling. Untreated symptomatic tears may cause permanent damage (arthritis), because the torn meniscus rubs on the surface of the joint like "sand in a ball-bearing". These tears are best treated early.
The word "chondromalacia" means cartilage (chondro) softening (malacia). This may occur in any joint but is commonly used to describe surface changes of the knee cap (patella). Patellar chondromalacia truly describes cartilage changes seen microscopically, but has been generalized to encompass the clinical condition. The patella, or kneecap, is an oblong bone which is embedded within the extensor tendon of the knee. The patella, increases the leverage of the extensor muscles (quadriceps) and acts also as a pulley, around the femoral groove. Both the patella and the femoral groove which it contacts, have smooth cartilage surfaces lubricated by synovial fluid (joint oil). The cartilage also absorbs enormous loads during daily activities. Walking on level ground exerts a contact force of one-half body weight. Climbing stairs increases the force to four times body weight. Arising from a squat can generate patellar forces up to eight times body weight. Chondromalacia may occur as a result of a direct blow to the patella, fracture or patellar dislocation, or more commonly, over a period of years because of wear and tear, patellar arthritis develops because of patellar maltracking. This occurs because of overuse, coupled with anatomic malalignment and supporting soft tissue imbalance. The anatomic factors responsible for alignment and patella tracking are: tibiofemoral angle (knock-knee or bow-leg), tibiofemoral rotational alignment, patellar and femoral groove shape and congruity, and capsular and muscular balance. In general, "maltracking" from any cause exposes the cartilage of patella and femur to localized excessive load and accelerated wear. The condition is more common in women and is frequently seen during adolescence. It is often associated with activities which induce high patella femoral loads such as hill climbing, cross-country running, jumping, and squatting.