Today we are going to consider how trigger points can contribute to shoulder impingement and pain. Before we go too deep into this, keep in mind that impingement in the shoulder is normal. Shoulder impingement is a quick and dirty diagnosis tossed around by medical providers when they aren’t quite sure what the heck is going on. This is where a full evaluation from your physical therapist can help you achieve long lasting improvements. Looking at the quality of your tissues and joints, as well as how well you move, paints a much clearer picture.
Shoulder impingement (subacromial, to be more specific): it is hypothesized that pain at the shoulder is secondary to the compression or abrasion of the subacromial structures when the arm is elevated.
Research studies have shown a link between trigger points and shoulder pain associated with shoulder impingement. Treatment of trigger points may be the answer you’re searching for. Like I said before, impingement in the shoulder is normal! You have a nicely sized bursa in your subacromial space to allow for this type of compression. Research studies suspect that when an abnormal amount of load (increased repetitions/force) is applied to this space that symptoms can occur.
Two suspected reasons for abnormal shoulder impingement:
- Functional Impingement
Your rotator cuff muscles are doing a poor job of keeping the head of your humerus nicely aligned in the socket. This could be secondary to poor timing of the musculature, strength deficits, or even endurance deficits. Trigger points can actually alter each of these factors.
- Structural Impingement
This could be secondary to muscle and/or joint restrictions, and postural faults. In some cases the structure of your bones may limit your range of motion at the shoulder joint. Not everyone is built to repetitively press big weights overhead. I know what you are thinking…. “It can’t be true!” It is.
What is a trigger point?
Trigger points are hyperirritable nodules that can be palpated in muscle. Chemicals associated with pain are commonly found at the site of active trigger points (substance P, bradykinin and serotonin). Trigger points are strongly associated with myofascial pain, and can result in motor, sensory and autonomic symptoms.
Active Trigger Points: Trigger points that reproduce familiar pain.
Latent Trigger Points: Similar findings as active trigger points, without reproduction of familiar pain.
So where do trigger points come into play?
Three key findings were discovered in Hidalgo-Lozano, A. Et al.
- The more trigger points you have, the more pain you have at rest.
- Patients with an impingement diagnosis and more pain at rest have more active trigger points in their surrounding shoulder musculature (i.e. trapezius, infraspinatous, subscapularis and scalenes).
- Trigger points are known to alter muscle activation and cause poor movement quality.
- Likewise, impingement is also associated with altered muscle activation and poor movement quality (sometimes associated with muscle restrictions). This could mean that trigger points play a role in the muscle dysfunction identified in people with pathologic shoulder impingement (I say pathologic because shoulder impingement alone is a normal finding, as mentioned above).
- Patients with more trigger points report increased difficulty with daily activities.
What could these findings mean for me?
Treatment for trigger points could significantly improve your shoulder pain and improve your ability to move your arm without pain. Numerous studies have found treatment for trigger points to be effective in managing pain local to the shoulder. Self-treatment of trigger points can be performed in a variety of ways. I recommend lacrosse balls, tennis balls, foam rollers and thera-canes for self-treatment.
Seeing a physical therapist skilled in trigger point treatment can help you precisely identify active trigger points that are contributing to your current symptoms. In clinic, I will spend time palpating different muscles during an evaluation. I will look to identify active trigger points that reproduce my patient’s complaints. In research and in my own clinical experience, dry needling of trigger points has lead to remarkable improvements in both pain and strength after only a couple treatment sessions.
- Shoulder impingement is normal.
- Abnormal, or pathologic, shoulder impingement is secondary to poor rotator cuff function and range of motion limitations; both structural and postural.
- Trigger Points are known to cause pain, poor muscle activation and altered movement patterns.
- Trigger points may be responsible for shoulder impingement and/or a result of shoulder impingement.
- Self-trigger point treatment and dry needling are effective techniques for treating trigger points.
Dr. Michael Infantino, DPT
Bron C, de Gast A, Dommerholt J, Stegenga B, Wensing M, Oostendorp RAB. Treatment of myofascial trigger points in patients with chronic shoulder pain; a randomized controlled trial BMC Medicine. 2011;9:8
Hidalgo-Lozano A, Fernández-de-las-Peñas C, Alonso-Blanco C, Ge H-Y, Arendt- Nielsen L, Arroyo-Morales M. Muscle trigger points and pressure pain hyperalgesia in the shoulder muscles in patients with unilateral shoulder impingement: a blinded, controlled study. Exp Brain Res. 2010;202(4):915-925 197
Hidalgo-Lozano, A., Fernández-de-las-Peñas, C., Díaz-Rodríguez, L., González-Iglesias, J., Palacios-Ceña, D., & Arroyo-Morales, M. (2011). Changes in pain and pressure pain sensitivity after manual treatment of active trigger points in patients with unilateral shoulder impingement: A case series. Journal Of Bodywork & Movement Therapies, 15(4), 399-404. doi:10.1016/j.jbmt.2010.12.003
Mense S. Muscle pain: mechanisms and clinical significance. Dtsch Arztebl Int. Mar 2008;105(12):214-219
Shah JP, Danoff JV, Desai MJ, et al. Biochemicals associated with pain and inflammation are elevated in sites near to and remote from active myofascial trigger points. Arch Phys Med Rehabil. 2008;89(1):16-23