Successful results of surgical procedures for sports injuries are heavily dependent on postoperative and injury rehabilitation. The catabolic effect of surgery and injury places the injured athlete in a position of diminished functional ability and inhibition. For many athletes, this impaired position is a new adventure, often testing the individual’s patience, mental drive, and work ethic.
Using mechanical engineering concepts, Steindler first described the kinetic chain concept in 1955 and sought to describe various types of exercise conditions with this new concept. The mechanical engineering definition of the kinetic chain describes a series of interconnected joints, fixed proximally and distally. In this system, the movement of one joint has an effect on all joints above and below.
Steindler separated the mechanical engineering definition into two states—open and closed kinetic chain. He described the open-chain state as a peripheral extremity that is able to move freely, such as waving the hand or the swing phase of the gait pattern. The closed kinetic chain state was described as when the distal segment meets considerable resistance, as it does with a pull-up or squat.
Considerable ambiguity exists when describing various exercises by open- and closed-chain definitions. Confusion sometimes exists when determining what is a true closed kinetic chain state. A more simple and precise description may be weight-bearing and non–weight-bearing exercises and the relationship to the anatomic structure. During progression of the exercise program, the injured athlete is placed in different positions that could cause harm to the healing tissue. Knowledge of the kinetic chain has allowed us to further advance safety and protection while rehabilitating the injured athlete. Although the language of closed and open kinetic chain may be ambiguous, it allowed a method of communication among physicians and therapists during the early years of anterior cruciate ligament and posterior cruciate ligament reconstructions.
During the initial stages of rehabilitation, the primary goal is to restore muscle function. Without the protection of the dynamic forces supplied by muscle, undue forces will be placed on the static restraints that act in concert with muscle to provide joint stability and equilibrium. Altered mechanics could lead to undesired forces to the articular cartilage, healing graft, and overloaded tendon tissue.
Muscle inhibition appears to be focused on our antigravity muscles. One possible explanation is that the antigravity muscles have a higher percentage of slow-twitch type I muscle fibers that may be more sensitive to the inhibitory impulse that is present when swelling and pain are present in the joint. Immobilization has been proved to be detrimental to type I muscle fibers. It has been shown that the vastus medialis obliquus of the quadriceps has a richer saturation of type I muscle fibers over the remaining quad muscles. This phenomenon may be a cause of rapid shrinking and inhibition of the vastus medialis obliquus while under the influence of pain or swelling, leading to decreased excitability of quadriceps motoneurons. The Ruffini endings are stimulated when an effusion is present, alerting and activating central structures regarding the current state of the knee joint. Palmieri-Smith and colleagues described the influence on a step-down maneuver during quadriceps inhibition, which demonstrated that greater ground reaction forces were induced to the knee while under the influence of experimentally induced effusion in the normal knee. This finding further supplants the theory that a weak knee will be unable to slow down forces external to the joint. A lack of dynamic shock absorption from the quadriceps may lead to breakdown of the “golden” protection of the joint, the articular cartilage. The same effects are present in the antigravity muscles of the shoulder: the posterior rotator cuff muscles (infraspinatus and teres minor).
To combat the inhibitory effects on muscle atrophy and resultant weakness, several modalities can be implemented. One method of reversing muscle inhibition is the use of biofeedback. A threshold of activation is set according to the patient’s ability to elicit an electrical signal through nerve depolarization. A goal is then set on the instrument for the patient to attempt to reach. The visual feedback to the patient is the use of light-emitting diode lights on the face of the instrument. When the goal has been reached, the lights change color, indicating a successful contraction. Muscle stimulation without active contraction has not been shown to be beneficial. Muscle stimulation in coordination with active muscle contraction has been shown to help combat muscle atrophy. Biofeedback has been shown to be more effective than electrical muscle stimulation in restoring muscle strength to postoperative patients.
Adhesions and Arthrofibrosis
A stiff joint alters the rehabilitation protocol. The most unhappy and debilitated sports medicine patient is one who has lost function because of stiffness of his or her joint. It is believed that some persons have a greater propensity to experience adhesions in the joint. Many studies have documented ill effects that result from postoperative joint adhesions. One of the factors that helps to prevent loss of motion is muscle activation. Paulos and colleagues described the altered position of the patella that occurs postoperatively after anterior cruciate ligament reconstruction. Patella infra is the result of immobilization and a lack of quadriceps contraction. If the quadriceps is firing appropriately after surgery, a natural superior glide of the patella occurs, preventing the patella from drifting inferiorly because of fat pad contracture to the proximal tibia. Manual superior glide mobilizations are required in the severely quadriceps-inhibited knee. These manual mobilizations are performed with the knee in full extension, with no quadriceps activity present. Aggressive force may be used to glide the patella superiorly until quadriceps function takes over the superior gliding movement of the patella.
Rehabilitation devices have been created to help combat the restrictions associated with the development of a stiff joint. These devices use overpressure in a controlled manner to help lengthen the scar tissue or prevent scar formation, and they place the patient in control. Additionally, they may allow for more relaxation of the musculature so that the scar tissue can be addressed. If pain is too severe, a muscular cocontraction limits the ability to address the culprit that is limiting motion—adhesion formation. Long-duration stretching is performed to fatigue scar tissue.