Epidemiology of Shoulder Pain
Shoulder pain is a common musculoskeletal condition that is is recognised as a disabling problem and can be associated with substantial economic burden. The pain and disability associated with shoulder pain can have a large impact on individuals and their families, communities, and healthcare systems affecting daily functioning, and ability to work. It is the third most common musculoskeletal complaint presenting to physiotherapy. 
The definition of shoulder pain is not so clear cut and in epidemiological studies defining shoulder pain symptoms presents a number of difficulties secondary to the complex interrelations between the shoulder and adjacent areas and the frequent occurrence of referred pain which make clinical case definition problematic. The aetiology of shoulder pain is diverse and includes pathology originating locally from the shoulder such as the glenohumeral joint, acromioclavicular joint, sternoclavicular joint, rotator cuff, and other soft tissues within the shoulder complex but can also be referred from other structures, such as the neck, or other visceral organs.  The extent of tissue damage observed on clinical imaging does not correlate with shoulder pain intensity, thus the relevance of diagnosing structural pathology in people with shoulder pain has been challenged by many in research and clinical practice. Similarily it has been shown that in the general population anywhere from 20 - 40% of individuals have asymptomatic rotator cuff tears, which suggests that structural pathology may not fully explain the perception of shoulder pain and highlights the potential for diagnostic labels to mislead treatment.In practice, therefore, ‘shoulder pain’ has been applied as an all encompassing term in many of the epidemiological studies available.
Here we will review some findings from the literature with regards to the incidence and prevalence of shoulder pain in the general population, age distribution, occupational and psychosocial risk factors associated with the onset of shoulder-related pain symptoms. 
Incidence figures ranged from 0.9-2.5% with average incidence of 29.3 per 1000 person-years over a period of 9 years, with specific incidences of ;
- 32.2 for women
- 26.2 for men
Mean incidence per 1000 person-years over a period of 9 years ;
- 22.2 in 18- 44 year olds
- 40.2 in 45 - 64 year olds
- 37.1 in 65+ year olds
Incidence of Specific Conditions;
- Rotator Cuff Tendinopathy incidence ranges from 0.3%to5.5%
- Traumatic dislocation of the Glenohumeral Joint is the most common joint dislocation with an incidence of 8.2 to 23.9 per 100,000 per year 
There is substantial variances in the estimated prevalence of shoulder pain, ranging anywhere from 1% up to 66%  . This can in part be as a result of the complex structure of the shoulder and close functional biomechanical association with adjacent areas, including the spine. Some further causes of variability in reporting relate to that fact that the shoulder may be a primary or secondary source of pain, so many authors and clinicians tend to summarise such a presentation simply as shoulder pain syndrome. 
- Point Prevalence ranging from 6.9% - 26%
- 1-Month Prevalence ranging from 18.6% - 31%
- Annual Prevalence ranging from 4.7% - 46.7%
- Lifetime Prevalence ranging from 6.7% - 66.7%
- Chronic Pain Prevalence ranging from 15.5% - 41% rising from 23% in 18 - 24 year olds, reaching a peak of 50% in 55 - 64 year olds 
Prevalence related to Specific Conditions:
- Primary Adhesive Capsuitis reported prevalence from 2 % to 5.3 %, mainly affecting women, with sedentary jobs, non-dominant shoulder, over 40 years old 
- Secondary Adhesive Capsulitis related to Diabetes Mellitus and Thyroid Disease reported prevalence from 4.3% and 38% 
- Rotator Cuff Related Abnormalities reported prevalence ranged from 9.7% - 62% 
Prevalence is generally higher in women (15% - 26%) than in men (13 - 18%), with a greater number of women presenting to Primary Care. 
Prevalence increased linearly with age while incidence peaked at around 50 years then remained static at around 2%. Most prevalent in middle age (45 - 64 years, from 21 - 55%), which may be attributed to the normal aging process of shoulder structures including the rotator cuff but is also common in the younger age group (adolescents aged 12 - 18 years, from 12 - 57%), which can be attributed to a postural relationship associated with increased periods of sitting, and increased technology use. 
Shoulder was the second most commonly affected site for musculoskeletal pain behind low back pain in the Netherlands. Some other interesting findings from that study include that 30% described continuous pain, while 55% had recurrent pain with mild pain more common (70%) than severe pain (15%).  While Koojman et al suggest that shoulder pain is the third most common musculoskeletal complaint presenting to physiotherapy , representing 14% of annual referrals to physiotherapy outpatient services in the UK.
Risk factors for shoulder pain share many similarities with other musculoskeletal conditions such as genetics, hormonal influences, lifestyle factors such as smoking, alcohol consumption, comorbidities, level of education and sedentary lifestyle , sleep disorders , biochemical, patho-anatomical, peripheral and central sensitisation and sensory-motor cortex changes  and a raft of psychosocial factors such as depression, anxiety, poor coping skills, somatisation . In particular excessive and mal-adaptive load imposed on the tissues appears to be a major influence in certain disorders of the shoulder such as Rotator Cuff Related Shoulder Pain .
Work-related risk factors associated with the onset of shoulder pain cited in the literature include repetitive work in particular overhead activities or working above should, high force demand and vibration, work-related posture, computer work and psychosocial factors including stress, job pressure, social support and job satisfaction.
When we look at specific shoulder conditions rotator cuff disorders are associated with excessive overloading, instability of the glenohumeral and acromioclavicular joints, muscle imbalance, adverse anatomical features, age related rotator cuff degeneration, ischaemia, and musculoskeletal diseases that result in rotator cuff atrophy.  Adhesive Capsulitis risk factors include being female, older age, history of shoulder trauma, surgery, diabetes, cardiorespiratory disorders, cerebrovascular events, thyroid disease, and hemiplegia.
PrognosisApproximately 50% of new episodes of shoulder pain resolve in eight to twelve weeks, but as many as 40% of cases persist for longer than one year with rates of recurrence and chronicity of shoulder pain rated as moderate to high.  Many people with shoulder pain do not experience a complete resolution of symptoms, and between 40% to 50% of those who experience shoulder pain report recurrence within 1 to 5 years later. While up to 13.6% were still attending medical services with a shoulder problem during the third year of follow-up. In a 2003 study of Danish workers with shoulder tendinopathy, average symptom duration was 10 months or less, with 25% of workers continuing to experience symptoms at 22 months. 
Poor prognosis is associated with increasing age, female sex, severe or recurrent symptoms at presentation and associated neck pain. In particular high baseline pain and previous episodes of shoulder pain are associated with an unfavourable outcome. A favourable prognosis is associated with mild trauma or overuse before onset of pain, early presentation and acute onset.
Research shows that associations between prognostic factors and outcome are often inconsistent, which may be due to type II error or heterogeneity on a number of levels including treatment selection, adherence or outcome measure. Only two baseline prognostic factors consistently demonstrated anassociation with outcome in two or more studies; duration of shoulder pain and baseline function. 
The economic burden due to disorders of the shoulder is high, and includes costs of treatment, and lost wages. One study in the UK reported approximately 1% of adults in the UK consult their medical practitioner with estimated costs of £310 million in the first 6 months, additional surgical costs for procedures were estimated at approximately £30 million/year, with up yo 50% of these costs related to sick leave from paid employment.
Relevance to Physiotherapy
Although some acute episodes of shoulder pain resolve spontaneously, as many as 50% of all new episodes of shoulder pain still continue to show symptoms or recurrences at 6 months.with as many as 40% still with symptoms at 1 year. For managing shoulder pain the strongest evidence currently is for exercise. Physiotherapists have a detailed understanding of the shoulder complex, related pain mechanisms and exercise prescription which makes them well placed to be the experts to help individuals with shoulder pain return to normal function, therefore reducing burden of shoulder pain.
- Kooijman MK, Swinkels ICS, Leemrijse CJ, de Bakker DH, Veenhof C. National Information Service of Allied Health Care. 2011.
- Barrett E. Examining the Role of Thoracic Kyphosis in Shoulder Pain [Phd Thesis]. Limerick: University of Limerick. 2016.
- Pope DP, Croft PR, Pritchard CM, Silman AJ. Prevalence of Shoulder Pain in the Community: The Influence of Case Definition. Annals of the Rheumatic Diseases. 1997 May 1;56(5):308-12.
- Murphy RJ, Carr AJ. Shoulder Pain. BMJ clinical evidence. 2010;2010.
- Pribicevic M. The Epidemiology of Shoulder Pain: A Narrative Review of the Literature. InPain in Perspective 2012. InTech.
- Miniaci A, Mascia AT, Salonen DC, Becker EJ. Magnetic resonance imaging of the shoulder in asymptomatic professional baseball pitchers. American Journal of Sports Medicine 2002; 30(1): 66-73.
- Connor PM, Banks DM, Tyson AB, Coumas JS, D’Alessandro DF. Magnetic resonance imaging of the asymptomatic shoulder of overhead athletes: a 5-year follow-up study. American Journal of Sports Medicine 2003; 31(5): 724-727.
- Templehof S, Rupp S, Seil R. Age-related prevalence of rotator cuff tears in asymptomatic shoulders. Journal of Shoulder and Elbow Surgery 1999; 8: 296-299.
- Worland R, Lee D, Orozco C, Sozarex F, Keenan J. Correlation of age, acromial morphology, and rotator cuff tear pathology diagnosed by ultrasound in asymptomatic patients. Journal of the Southern Orthopaedic Association 2003; 12(1): 23-26.
- Yamamoto A, Takagishi K, Osawa T, Yanagawa T, Nakajima D, Shitara H, Kobayashi T. Prevalence and risk factors of a rotator cuff tear in the general population. Journal of Shoulder and Elbow Surgery 2010; 19(1): 116-120.
- Greving K, Dorrestijn O, Winters JC, Groenhof F, Van der Meer K, Stevens M, Diercks RL. Incidence, prevalence, and consultation rates of shoulder complaints in general practice. Scandinavian journal of rheumatology. 2012 Mar 1;41(2):150-5.
- Brownson, P., Donaldson, O., Fox, M., Rees, J. L., Rangan, A., Jaggi, A., et al. (2015). BESS/BOA Patient Care Pathways. Shoulder & Elbow, 7(3), 214–226. http://doi.org/10.1177/1758573215585656
- Luime JJ, Koes BW, Hendriksen IJ, Burdorf A, Verhagen AP, Miedema HS, Verhaar JA. Prevalence and incidence of shoulder pain in the general population; a systematic review. Scandinavian journal of rheumatology. 2004 Mar 1;33(2):73-81.
- Struyf, F., & Meeus, M. (2013). Current evidence on physical therapy in patients with adhesive capsulitis: what are we missing? Clinical Rheumatology, 33(5), 593–600. http://doi.org/10.1007/s10067-013-2464-3
- Kelley, M. J., Shaffer, M. A., Kuhn, J. E., Michener, L. A., Seitz, A. L., Uhl, T. L., et al. (2013). Shoulder Pain and Mobility Deficits: Adhesive Capsulitis. Journal of Orthopaedic & Sports Physical Therapy, 43(5), A1–A31. http://doi.org/10.2519/jospt.2013.0302
- MD, T. T., BSc, B. L., BSc, B. T. R., & PhD, D. R. M. (2014). A systematic review and pooled analysis of the prevalence of rotator cuff disease with increasing age. Journal of Shoulder and Elbow Surgery, 23(12), 1913–1921. http://doi.org/10.1016/j.jse.2014.08.001
- Picavet HS, Schouten JS.Musculoskeletal Pain in the Netherlands: Prevalence’s, Consequences and Risk Groups, the DMC(3)-Study. Pain 2003167178
- Kooijman MK, Swinkels ICS, Leemrijse CJ, de Bakker DH, Veenhof C. National Information Service of Allied Health Care. 2011.
- May S. An Outcome Audit for Musculoskeletal Patients in Primary Care. Physiotherapy Theory and Practice 2003; 19: 189-198.
- Harvie P, Ostlere SJ, Teh J, McNally EG, Clipsham K, Burston BJ, et al. Genetic influences in the aetiology of tears of the rotator cuff. Sibling risk of a full-thickness tear. The Journal of bone and joint surgery British volume. 2004;86:696-700.
- Magnusson SP, Hansen M, Langberg H, Miller B, Haraldsson B, Westh EK, et al. The adaptability of tendon to loading differs in men and women. International journal of experimental pathology. 2007;88:237-40.
- Baumgarten KM, Gerlach D, Galatz LM, Teefey SA, Middleton WD, Ditsios K, et al. Cigarette smoking increases the risk for rotator cuff tears. Clinical orthopaedics and related research. 2010;468:1534- 41.
- Passaretti D, Candela V, Venditto T, Giannicola G, Gumina S. Association between alcohol consumption and rotator cuff tear. Acta orthopaedica. 2015:1-4.
- Dunn WR, Kuhn JE, Sanders R, An Q, Baumgarten KM, Bishop JY, et al. Symptoms of pain do not correlate with rotator cuff tear severity: a cross-sectional study of 393 patients with a symptomatic atraumatic full-thickness rotator cuff tear. The Journal of Bone and Joint Surgery. 2014;96:793-800.
- Lewis JS. Bloodletting for pneumonia, prolonged bed rest for low back pain, is subacromial decompression another clinical illusion? British Journal of Sports Medicine. 2015;49:280-1.
- Dean E, Söderlund A. Lifestyle factors and musculoskeletal pain. In: Jull G, Moore A, Falla D, Lewis JS, McCarthy C, Sterling M, editors. Grieve's Modern Musculoskeletal Physiotherapy. 4th ed. London: Elsevier; 2015.
- Cook JL, Rio E, Lewis JS. Managing tendinopathies. . In: Jull G, Moore A, Falla D, Lewis JS, McCarthy C, Sterling M, editors. Grieve's Modern Musculoskeletal Physiotherapy. 4th ed. London: Elsevier; 2015.
- McCreesh K, Lewis J. Continuum model of tendon pathology - where are we now? International journal of experimental pathology. 2013;94:242-7.
- Riordan J, Dieppe PA. Arthritis of the glenohumeral joint. Baillieres Clin Rheumatol 1989;3:607–626.[PubMed]
- Bonutti PM, Hawkins RJ. Rotator cuff disorders. Baillieres Clin Rheumatol 1989;3:535–550.[PubMed]
- Soslowsky LJ, An CH, Johnston SP, et al. Geometric and mechanical properties of the coracoacromial ligament and their relationship to rotator cuff disease. Clin Orthop 1994;304:10–17.[PubMed]
- Jobe FW, Kvitne RS. Shoulder pain in the overhand or throwing athlete: the rela- tionship of anterior instability and rotator cuff impingement. Orthop Rev 1989;18:963–975.[PubMed]
- Nash P, Hazleman BL. Frozen shoulder. Baillieres Clin Rheumatol 1989;3:551–566.[PubMed]
- Wohlgethan JR. Frozen shoulder in hyperthyroidism. Arthritis Rheum 1987;30:936–939.[PubMed]
- Oliva F, Osti L, Padulo J, Maffulli N. Epidemiology of the Rotator Cuff Tears: A New Incidence Related to Thyroid Disease. Muscles, Ligaments and Tendons Journal. 2014 Jul;4(3):309.
- Hopman K, Krahe L, Lukersmith S, McColl A, Vine K. Clinical Practice Guidelines for the Management of Rotator Cuff Syndrome in the Workplace. Port Macquarie (Australia): University of New South Wales. 2013;80.
- Littlewood C, May S, Walters S. Epidemiology of Rotator Cuff Tendinopathy: A Systematic Review. Shoulder & Elbow. 2013 Oct 1;5(4):256-65.
- Chester R, Shepstone L, Lewis JS, Jerosch-Herold C. Predicting Response to Physiotherapy Treatment for Musculoskeletal Shoulder Pain: Protocol for a Longitudinal Cohort Study. BMC Musculoskeletal Disorders. 2013 Jun 21;14(1):192.
- Littlewood, C. (2013). Contractile dysfunction of the shoulder (rotator cuff tendinopathy): an overview. Journal of Manual & Manipulative Therapy, 20(4), 209–213. http://doi.org/10.1179/2042618612Y.0000000005
- Winters JC, Sobel JS, Groenier KH, Arendzen JH, Meyboom de Jong B. The long-term course of shoulder complaints: a prospective study in general practice. Rheumatology 1999; 38: 160-163.
- van der Windt DA, Koes BW, de Jong BA, Bouter LM. Shoulder disorders in general practice: incidence, patient characteristics and management. Annals of Rheumatic Diseases 1995; 54(12): 959-964.
- Croft P, Pope D, Silman A. The clinical course of shoulder pain: case series in primary care. British Medical Journal 1996; 313: 601-612.