Scapular (Shoulder Blade) Instability Explained

In this article, we will look at another type of instability which is just as important: scapular instability. In the last article, we discussed the instability of the humeral head position as a result of poor control or strength of the lower rotator cuff muscles.

Scapular instability will often lead to shoulder pain. They are often associated with impingement syndrome as well. Like any stability muscles in the body, e.g. the Transversus Abdominus in the lower back, Vastus Medialis Oblique (VMO) in the knee or the rotator cuff in the shoulder, once there is pain or dysfunction, these stabilizer muscles tend to “switch off” until they are deliberately retrained. With the stabilizers not functioning optimally, the mechanics of the joint i.e. how it moves will change.

In the painful shoulder, the scapular position will often be different from the non-painful side. You will notice that the scapular is downwardly rotated when the outline of the scapular is traced out. This is usually obvious when comparing the shoulder position. The side with the downwardly rotated scapular will have a droopy shoulder. The control of the scapular is also poor. This can be seen in a quivering shoulder blade when the arm is raised sideways and lowered very slowly.

Components Of Shoulder

The shoulder consists of a ball and socket joint. To keep the structure stable, they are held intact passively by the labrum, the capsule and the ligaments. The socket is part of the scapula. The socket is now rotated downwards with a downwardly rotated (tilted downwards) scapular. This means that it is no longer in an optimal position to contribute to stability leading to shoulder mechanical dysfunction.

This downward rotation or tilt is due to muscle imbalance in the surrounding scapular. The muscles that encourage or maintain upward rotation are the Upper Trapezius, the Middle Trapezius, the Lower Trapezius, and the Serratus Anterior. These muscles are usually weak and have poor endurance hence downward rotation of the scapular occurs. With the scapular in a downward rotation, other muscles around the scapular get progressively tighter, aggravating and perpetuating the downward rotation. These muscles are the Levator Scapular and the Rhomboids. This explains why these two muscles are always painful when massaged.

Treatment For Scapular Instability

With the treatment of a painful shoulder, it is imperative that the scapular position and control are assessed together with the shoulder joint. It is not sufficient that deep tissue release is done over the Levator Scapular and the Rhomboid. Without retraining the muscle control around the scapular, the Levator Scapular and the Rhomboids will eventually tighten up again.

As part of the rehab plan for long-term recovery, the physiotherapist must retrain the specific muscles and the pattern of movement. This is so that there is an alternative to the current poor activation of muscle and movement patterns.

Experiencing shoulder pain? Click here to find out more about physiotherapy for shoulder pain relief and how Core Concepts can help.