Physiotherapy for the Unstable Shoulder
Rehabilitation of the unstable shoulder, be it with non-operative or post-operative management, should aim to optimise the performance of the shoulder muscles. When the arm is held out 90° at the side with the palm facing upwards, this is a position where the shoulder is at extreme risk of dislocation if a large force is applied to it (Fig. 7a). The aim for rehabilitation would be to strengthen the muscles which normally help to prevent inadvertent dislocation.
To achieve this, the physiotherapist must consider all parts of the shoulder; in particular, its muscles and tendons, ligaments, and neuromuscular control.
The rotator muscles of the shoulder, i.e. the rotator cuff, must work together to keep the shoulder still while moving the arm. Weakness affecting the balance of these muscles needs to be identified and corrected from the outset of rehabilitation.This is achieved by various resistance exercises using a "Theraband" (a tough elastic band).
Exercise with a Theraband tied to a doorknob, or some other stable point, is a useful means for strengthening the various muscles of the rotator cuff (Fig. 7b). This helps the patient return to sport and other normal activities.
Instability often occurs when the muscles responsible for stability tire. Hence, it is not only important to strengthen these muscles but also to improve endurance (the ability to maintain a contraction over a long period of time).
Two muscles at the back of the shoulder, the trapezius and serratus anterior muscles, are involved in positioning the scapula correctly. Exercises which help to strengthen these muscles are push-ups and rowing. However, all muscles around the scapula should be assessed to ensure their optimal funtion.
Tendon and ligament tension
Tendons (the fibrous tissue which joins muscle to bone) of the rotator cuff muscles blend with the capsule (the tough sack which surrounds the humerus and the glenohumeral joint) at their point of insertion. Upon contraction, the tendons help tighten the slackened capsule together with its built-in ligaments. This tensioning of the capsule helps hold the humeral head in the socket.
Normalising the range of motion, particularly when the capsule is loose, is an important aspect of rehabilitation. In situations of asymmetrical capsular tightness, the humeral head moves excessively in the opposite direction to the tightness. In the athlete who uses his/her arm overhead, posterior capsular tightness is not an uncommon finding. Capsular length can be restored to some extent by specific stretching and mobilising of the joint capsule. Where restoration of capsular length is crucial for preventing/rehabilitating anterior shoulder instability, surgery may be warranted.
This is achieved by exercising the unstable shoulder in positions which maximally challenge the shoulder muscles. Messages relating to joint position awareness (proprioception) are fed back to the brain via receptors contained in the capsule and ligaments of the shoulder. When these receptors detect a situation of potential tissue damage, the brain sends a signal to the muscles to contract and thus reposition the joint to decrease the mechanical stress on the surrounding areas.
Exercises which involve weight bearing through the arm help stimulate proprioception. Plyometric exercises, those which involve rapid changes of direction when the muscle is being stretched one way and then quickly shortened the other way, are good to help with re-educating neuromuscular control. An example of this is vigorously bouncing a ball (Fig. 7c). This exercise should be commenced by bouncing the ball by your side on the ground and then progressed to overhead against the wall where the shoulder is more challenged.
To ensure shoulder stability, all parts of the shoulder complex need to be considered. In order to provide a stable platform under the humeral head, the scapula and humerus need to move together and the orientation of the shoulder cavity needs to adjust in response to changes in arm position.
In conclusion, shoulder stability for functional activity is dependent upon a balanced interaction between the shoulder muscles, tendons, ligaments, and nerves. Rehabilitation for the unstable shoulder should focus on more than just a "loose" joint. It should be individualised according to assessment findings and tailored in accordance with the activity demands of the patient.
Warning: Remember, in the case of shoulder dislocation, always seek expert medical advice and aid.