Shoulder impingement syndrome is a common painful condition, which arises when the tendons inside the shoulder joint, known as the rotator cuff, get trapped in the small space underneath the acromion, the hooked shaped bone process attached to the front of the shoulder blade (scapula). This can lead to inflammation and sharp pinching pain initially. Over time damage and weakness of the rotator cuff tendon occurs, which may eventually result in a partial or full thickness tear if untreated.
The condition can arise gradually and insidiously or it can be a consequence of trauma to the shoulder joint. Factors which reduce the already small space under the acromion can increase the likelihood of impingement. These include swelling of the rotator cuff tendon itself (as a result of trauma or overuse),bony spurs and calcium build up on the tendon (usually related to age and overuse) as well as inflammation of the bursa (fluid filled sac) which lies between the acromion and the rotator cuff tendon
Sharp pain is usually felt in the shoulder joint or upper arm area when the arm is lifted overhead. Sometimes the shoulder joint passes through an arc of pain, which then eases as the arm goes towards full elevation. This arc corresponds with the range of movement where there is most contact between the acromion and the tendon. Catching pain can also be felt when lowering the arm. Passive movements are usually less painful than active movements because the tendon is not contracting and therefore less compressed. It may be uncomfortable to lie on the affected shoulder and it may ache at rest if there is inflammation already present.
If you have these symptoms then physiotherapy is usually the first course of treatment.
Your physiotherapist will examine closely the biomechanics of your shoulder joint movement. The way in which you lift the arm can really affect how much space there is for the tendon to move under the acromion. They will be looking at the following:
1. The stabilisation of the shoulder blade (scapula)
The acromion process is attached to the scapula. When we lift our arm the scapula rotates upwardly slightly, a movement which is controlled by the scapula stabilising muscles: the serratus anterior, upper, middle and lower fibres of trapezius. If there is weakness or imbalance in these muscles then the rhythm of this movement is affected and exaggerated angling of the acromion can occur leading to mechanical impingement.
2. Instability of the glenohumeral (shoulder) joint
If there is laxity in the ligaments of the shoulder joint itself perhaps as a result of a recent dislocation or connected with some underlying hypermobility (excessive movement) syndrome, then the head of the humerus can move forwards and upwards more when the arm is lifted causing impingement.
3. Imbalance of the rotator cuff and deltoid muscles
The deltoid muscle is the primary mover of the shoulder joint when we lift the arm. However the rotator cuff muscles have a roll together in depressing the head of the humerus (shoulder bone) as the arm is elevated. If there is weakness of the rotator cuff tendons then the humeral head can move upwards more making impingement more likely. In this way a shoulder impingement becomes a viscous circle of pain because the rotator cuff tendons are further weakened by the impingement, making them even less able to stabilise the humeral head in elevation.
- Posture re-education
Posture is often an important factor, especially in insidious onset shoulder impingement. There is evidence that a more forward position of the shoulder joint is more likely to create impingement. Sway back standing postures or sitting bent over a computer desk can also result in muscle imbalances of both the scapula and glenohumeral muscles.
Your physiotherapist can help you to address these postural issues, using various feedback techniques such as kinesiotaping. Pilates can be a very good method of addressing global postural issues, which may be contributing to your shoulder impingement.
- Stretching and massage
Certain muscles groups may present as tight or short often as a result of poor posture. This can affect both the resting position and the movement of the scapula. Your physiotherapist may use massage techniques to help regain length of the muscles and combine them with some home stretching techniques.
Common muscles affected include: pectoralis minor and major, latissimus dorsi, anterior deltoid and levator scapulae
- Strengthening exercises
Muscle imbalances usually underlie any tightness’s so stretching must be combined with addressing weaknesses in other muscles groups.
The most common muscles which are found to be weak are the scapular stabilising muscles, particularly the serratus anterior and the middle and lower fibres of trapezius as well as the rotator cuff tendons themselves.
Your physiotherapist will prescribe exercises for these muscles groups, which will need to be closely monitored initially to make sure you are maintaining good posture and form.
- Addressing underlying instability and proprioception
Proprioceptive exercises, which stimulate the receptors in the ligaments overlying the joint in order to trigger a more effective co-contraction of the muscles and augment stability of the joint, may be given in conjunction with kinesiotaping.
It is difficult to place a time on recovery, especially for non-traumatic impingement as the movement patterns contributing to the impingement may be very longstanding and therefore take a long period of time to change. As a rough guide you should expect to be feeling some amelioration of your symptoms within 4-6 weeks of treatment. It may take several months of rehabilitation exercises to recover fully.
If your pain is not improving and it is uncomfortable to do your rehabilitation then you may be referred for further investigations with a sports physician or orthopaedic consultant. An ultrasound scan is often used to look at the movement of the tendon whilst you lift the arm. This can help to identify more precisely the point where the tendon is getting impinged and may indicate more internal causes of the impingement such as the presence of an inflamed bursa. An MRI scan can also give further details as to the causes of persistant impingement such as the presence of bone spurs or calcium build up.
A course of anti-inflammatories are usually prescribed initially for pain and a steroid injection may then be offered under ultrasound guidance. If this does not ameliorate the symptoms alongside physiotherapy after around 6 months then surgery, usually arthroscopic (key hole), to debride the tendon, remove the bursa or remove part of the acromion bone (acromioplasty)may become necessary.
Even in these more severe cases, once pain has been dealt with it is still necessary to address the factors discussed above (posture, instability and muscle imbalances) which may have been significant in developing the initial impingement and will be important to prevent re-occurrence.
By Nikki Richards MPHTY, BSc(Hons) MCSP
Narvani, A (2014). Key Clinical Topics in Sports and Exercise Medicine. JP Medical Limited