A Review of Open and Closed Kinetic Chain Exercise
Following Anterior Cruciate Ligament Reconstruction
|Figure 1 - Anatomy of the Knee|
Some of the therapists tend to agree that open kinetic chain exercise (OKCE) benefits the ACL the best. While some therapist believe that closed kinetic chain exercise (CKCE) are superior to OKCE. Recently, ACL ruptures have become the most common knee injury involved in the world of sports. There are approximately 250,000 ACL injuries in a given year (2). These injuries occur due to shear force placed on the ligament during any type of decelerating, turning, planting and cutting, and different types of landings. The ACL can only with stand 400 pounds of pressure at any given time, injuries become more common in high impact sports (10). With injuries becoming more frequent, rehabilitation is becoming more important. The purpose of this review was to determine which form of kinetic chain exercise, open or closed, is most beneficial following ACL reconstruction. We analyzed the areas that are most crucial during rehabilitation, strain, stability, joint force, range of motion (ROM), and strength. We believe that following ACL reconstruction, the safest Kinetic Chain Exercise will decrease stress, strain, and an increase in stability as well as range of motion (11)
During any exercise regiment, whether for rehabilitation purposes or for strengthening purposes, there are two types of Kinetic Chain Exercises used. The first is Open Kinetic Chain Exercises (OKCE). These exercises are performed typically were the foot is free to move. These exercises are typically non-weight bearing, with the movement occurring at the knee joint (4). If there is any weight applied it is applied to the distal portion of the limb. Examples of these exercises would be knee extensions and straight leg raises. OKCE concentrates on a strong quadricep contraction, which will strengthen the quadriceps and restore quadricep power output (8).
The second exercise used is Closed Kinetic Chain Exercise (CKCE). CKCE are performed where the foot is fixed and cannot move. The foot remains in constant contact with the surface, usually the ground or the base of a machine (8). These exercises are typically weight bearing exercises, where an athlete or patient uses their own body weight and/ or external weight. When external weight is added, it is usually rested across the back of the shoulders or the front of the chest. Examples of these exercises would be the Squat (both front and back), Leg Press, Lung, Power Clean, and Snatch. CKCE concentrates on a co-contraction of the quadriceps, hamstrings, hip flexors, soleus, and gastrocnemius muscles (9). In addition, this is a multi-joint movement, which focuses on the knee, hip, and ankle. CKCE are labeled as being "sport specific movements" (11).
During Kinetic Exercises, there are typically two kinds of external forces: shear and compression. Figures 2 and 3 give examples of each type of force. Figure 2 shows the angles of shear force placed on the knee joint during OKCE and CKCE. Figure 3 shows the ACL with shear and compression forces placed upon it (6).
|Figure 2 - Shear force during kinetic exercises|
Shear force, is the force which causes a disruption of the ACL by shifting the tibia anteriorly and the femur posteriorly. This is caused from the strong contraction of the quadriceps, which is typical of the Open Chain Exercise. This force, which is placed on the front of the knee, places a large amount of stress on the ACL.
Compression force is caused from a strong external force placed on the knee, which pushes the head of the femur together with the head of the tibia. This external force causes stability in the knee and a decrease in shear force. Compression forces are common in Closed Chain Exercises (3, 6).
Following ACL reconstruction, the rehabilitation is the most important aspect of restoring the knee joint back to normal levels of competition. Over the past decade there have been a number of studies that focus on the rehabilitation of the ACL (5). Due to the extensive research in this field there are still differences in opinions among many people involved in the athletic community (11).
Koch (6), in a popular magazine essay, states CKCE produces a minimal amount of shear force, while OKCE produces a great amount of shear force. When the knee is extended during Kinetic Chain Exercises, there is a strong contraction of the quadriceps. Koch found that with CKCE there is a co-contraction of the quadriceps and hamstrings (6). This reduces shear force placed on the knee by stabilizing the knee joint. Opposing to OKCE which increases shear force on the knee joint. This is caused from the lower leg shifting anteriorly which places a significant amount of stress on the ACL (Fig.'s 2 & 3).
|Figure 3 - Joint Forces|
Previous research performed comparing OKCE and CKCE found that CKCE was a safer and more beneficial from of exercise. Pincivero et al. (12) found that CKCE reduced shear force and increased compression force in the knee joint (Fig. 3). Also they found that CKCE activated the hamstrings, which increase knee stability. This occurs because with the contraction of the hamstrings, the quadriceps are neutralized from pulling the tibia forward, which decrease anterior tibial displacement (3).
Escamilla et al. (3) found that there was a large amount of quadricep activity during both exercises (quadricep contraction causes anterior tibial displacement). They found that strain place on the ACL during exercise is directly related to the shear force placed on the knee joint (3). When shear force is decreased this leads to a decrease in anterior tibial displacement. During CKCE the hamstrings are contracted, which reduces anterior tibial displacement. These results are similar to Jenkins et al.'s study (5). This study found that OKCE increases anterior displacement of the tibia. In addition, shear force is increased with OKCE.
In 1997 Fitzgerald (4) found that there were no significant differences between OKCE and CKCE. In this study Fitzgerald believes there is a place for both kinetic exercises during ACL rehabilitation.
Rehabilitation is the most important stage following ACL rupture. It is very important to understand what each form of kinetic exercise does to the knee joint (1). As coaches, trainers, physicians, and therapists we must understand the strain, joint forces (Fig. 3), and torque placed on the knee during each exercise. Also we must acknowledge which exercises, cause stability, an increase in compression force, as well as increased ROM, which will benefit the patient during rehabilitation.
The most important aspect is to return the athlete back to pre-injury competition level, as safe as possible (11). In order to do this we must utilize the exercises that will prevent re-injuring the repaired ACL. This review of literature found that Closed Kinetic Chain Exercises are the most beneficial during rehabilitation of the repaired ACL. Also CKCE are the most beneficial exercises used for prevention of future injuries of the knee joint (5, 6, 7).
We believe that there needs to be more research, which focuses mainly on comparing OKCE and CKCE. Of the studies found, only one study that supported OKCE and only one found that there were no significant differences between OKCE and CKCE. The rest of the studies concentrated on advantages and/ or disadvantages of either one Kinetic Chain Exercise or the other. There were only a few articles, which compared directly Open and Closed Kinetic Chain Exercises
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