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I t p a y s t o b e A B M P C e r t i f i e d : w w w. a b m p . c o m / g o / c e r t i f i e d c e n t r a l 101 Axis of rotation 2 Image 2: Pulling force when close to the axis of rotation. Image is from 3D4Medical's Essential Anatomy 3 application available on the App Store. ANATOMICAL CONSIDERATIONS A key step in considering appropriate treatment for a quadriceps tear is to consider the role of the knee extensor tissues. The quadriceps muscle group must generate a tremendous amount of power for forward propulsion and shock absorption in the knee. However, the anatomical design of the lower extremity has serious challenges for producing the high force loads required for knee extension. In a lever system like the knee, one link (the tibia) moves around an axis of rotation in relation to the other link (the femur). In general, when a pulling force is applied to the moving link from a position close to the axis of rotation, it is not able to generate powerful movements (Image 2). When the pulling force is farther away from the axis of rotation, much more power can be generated. The body meets this biomechanical challenge in two ways. The fi rst is by aligning the quadriceps muscle-tendon unit farther away from the axis of rotation. The patella is embedded within the quadriceps tendon, and as a result, acts as a fulcrum to pull the tendon farther away from the axis of rotation (Image 3). This allows the tendon to produce a greater force during muscle contractions. This is the primary biomechanical function of the patella. The second way the quadriceps gain more pulling power is to spread their attachment points over a broader area than just into the patellar tendon alone. Most anatomy texts show all of the quadriceps' fi bers blending into the patellar tendon, but in reality, many of them are connected to the patellar retinaculum (Image 1). The pulling force of the quadriceps is then transmitted through the retinacular tissues to the tibia. It is this factor that is of key importance in Patrick's case. Patrick's quadriceps tear extended through a signifi cant amount of the retinacular tissues. These tissues are richly innervated so the injury was very painful. The retinacular tissues are not as highly vascularized as muscle tissue, which poses some interesting challenges for the healing process because decreased vascularity can impair the speed of tissue healing. It's likely that some of the torn muscular fi bers healed faster than the retinacular fi bers. Because the tear occurred through muscle and retinacular tissue, it caused a massive amount of scar tissue. The added tissue and binding of the scarring impede the stretching movements necessary to regain proper motion. If surgery is necessary, the likely surgical approach would involve scraping the scar tissue loose—a fairly invasive procedure. This would also cause further scarring in the area, which would be detrimental to the overall treatment goal of increased tissue pliability. Consequently, the primary goals of the massage treatment will be to reduce the excessive scar tissue fi brosity and help regain range of motion in order to avoid surgery. A key step in considering appropriate treatment for a quadriceps tear is to consider the role of the knee extensor tissues. 3 The patella is a fulcrum that pulls the tendon farther away from the axis of rotation. Mediclip image copyright (1998) Williams & Wilkins. All rights reserved.