Clinical Evaluation of the Knee

Abstract

The knee joint consists of three bones — the femur, tibia, and patella — with three areas of articulation. The important soft-tissue structures of the knee include the four major ligaments — the anterior cruciate, posterior cruciate, and medial and lateral collateral ligaments — the joint capsule, the medial and lateral menisci, the quadriceps tendon, and the patellar tendon. The menisci are fibrocartilaginous structures located between the tibiofemoral articulations; they increase stability and distribute contact forces on the articular cartilage (Fig. 1 and 2). Common Knee Injuries All the bones and soft tissues of the knee are subject to injury. The most common problems that are reported in a physician’s office are related to soft-tissue inflammation, injury, or arthritis. Injuries to soft tissue and injuries resulting from overuse are often caused by reproducible mechanisms of physical trauma or forces. Fractures are less common and include fractures of the tibial plateau, the femoral condyles, or the patella. Knowledge of the mechanisms of knee injury can be essential to making an accurate diagnosis. An injury caused by valgus stress to the knee can result in medial collateral ligament strain or rupture, and an injury caused by varus stress can result in lateral collateral ligament strain or rupture. Abrupt noncontact deceleration or twisting and pivoting with simultaneous valgus stress to the knee can cause rupture of the anterior cruciate ligament, whereas abrupt posterior translation of the tibia can result in rupture of the posterior cruciate ligament. Twisting and pivoting of the knee while it is bearing weight can cause a meniscal tear. Overuse injuries are often manifested as pain in the structure subject to repetitive stress. For example, repetitive jumping can lead to patellar tendonitis, also called jumper’s knee, whereas repeated application of direct pressure to the patella through kneeling can cause prepatellar bursitis, sometimes referred to as housemaid’s knee. History Obtaining a complete history is the first step in determining the cause of knee pain. The key elements include location and characterization of pain, mechanism of injury, sound of a “pop” at the time of injury (which can indicate a ligamentous tear or fracture), immediate or delayed swelling, recent infections, ability to bear weight, locking sensation or instability (or incidents of subluxation), and prior injuries to the joint.