Who gets itEmerging evidence
Across 94 studies of 10,973 swimmers, the shoulder was the commonest injury site, and pooled shoulder injury rates were 34% in competitive, 46% in "amateur" and 46% in elite swimmers. In 80 young elite swimmers, 91% had had shoulder pain; about 1 in 5 female swimmers in every age group, masters included, had pain with disability; and shoulder pain lasting 3 weeks or more was as common in masters as in college swimmers (48% against 47%). Current pain that interfered with swimming rose from 10% of age-group swimmers to 26% of the US national team.
We found no study of people who swim for fitness on their own, so these figures come from club, college, elite and masters swimmers. Many swimmers train through the pain: most teenage club swimmers in one survey thought mild to moderate shoulder pain was normal and should be put up with to finish training, most swam with it, and 73% used painkillers to manage it.
Sources 1, 2, 3, 4, 5, 6
What "swimmer's shoulder" coversStrong evidence
The term was coined in 1974 for pain at the front of the shoulder during and after training, first blamed on the rotator cuff being pinched under the arch of the shoulder blade. Reviews now use it as an umbrella for several problems that can occur together: an overloaded rotator cuff (mostly the supraspinatus tendon), looseness and instability, a shoulder blade that moves unevenly, damage to the labrum (the rim of the socket) and, rarely, a trapped nerve. It names the situation, not the structure.
In 52 young elite swimmers who had scans, 69% had supraspinatus tendinopathy, and the more hours and distance they swam, the likelier it was. In 49 painful shoulders of competitive swimmers, most showed signs of impingement together with extra movement of the ball in the socket. At keyhole surgery in 18 swimmers whose pain hadn't settled, wear of the labrum (61%) was found more often than impingement (28%). In masters swimmers, biceps and supraspinatus tendon changes were common and went with pain.
Sources 7, 8, 9, 10, 11, 2, 12, 13, 14
Load: how much, and how fast it roseEmerging evidence
Swim-training volume went with shoulder pain in adolescents across 12 studies, but a review of 15 studies found no consistent link between training load and pain, and another found moderate evidence against training frequency as a risk factor. What stands out is the sudden jump. In 201 youth swimmers followed for two seasons, a high ratio of recent to usual training load predicted shoulder pain that interfered with training (about 4 times the odds), and in 37 college swimmers, very big weeks and sudden spikes went with about 25 times the odds of injury, with 7 of 12 injuries on a winter training camp. The margins of uncertainty around both figures were wide.
In the youth study, weaker endurance in the muscles at the back of the shoulder also predicted pain. Over half of college and masters swimmers with shoulder pain said more distance or intensity brought it on.
Sources 15, 16, 17, 18, 19, 4
Loose shouldersEmerging evidence
Elite swimmers' shoulders are looser than recreational swimmers', partly inborn and partly from training, and reviews put general joint looseness at anywhere from 20% to 62% of swimmers. Some looseness helps the stroke, but it asks the rotator cuff to work harder to keep the ball centred in the socket.
Athletes with hypermobile joints had about 3 times the odds of a shoulder injury (8 times with a hypermobile shoulder) on low-quality evidence, and looseness is one of four risk factors with moderate certainty in a review of 29 studies. But in elite swimmers it was only weakly linked with pain, so a loose shoulder is a reason to strengthen, not a diagnosis. The NHS suggests low-impact exercise such as swimming for joint hypermobility, with strength and fitness as the main treatment.
Sources 20, 10, 7, 21, 22, 2, 23
The stroke and the breathing sideMixed evidence
A hand that crosses the middle as it enters the water pinches the supraspinatus and biceps tendons, reviews say, and in a 3D lab study the high-risk features were a lot of inward rotation of the arm in the pull, late outward rotation in the recovery and little tilt of the shoulder blades. A dropped elbow is common (61% of 31 college swimmers in the pull), masters swimmers shortened the pull and recovery as they tired, more so if they had shoulder pain, and a dropped elbow or a wide entry can be the swimmer protecting a painful shoulder.
The advice on the hand itself differs: Swim England teaches a thumb-first entry, while a US study of college swimmers counted a thumb-first entry as a fault, linked with a dropped elbow. No study has linked either with pain, and no trial has tested changing technique.
Breathing to one side changed how each shoulder moved and rolled in lab studies, with more pinching positions on the breathing side in one, and uneven shoulder-blade movement was commoner on the side opposite the breathing side in 661 young elite swimmers. But a survey of 200 college and masters teams found no link between breathing side and shoulder pain.
Sources 7, 24, 25, 26, 18, 27, 28, 29, 30, 31, 32, 4
Hand paddles and kickboardsMixed evidence
Hand paddles made symptoms worse in top US swimmers who already had swimmer's shoulder, and paddles, kickboards, weights and stretching aggravated painful shoulders in a survey of 1,262 swimmers. But paddle use wasn't linked with having pain across 200 teams or in 187 college swimmers, and paddles didn't change the time spent in pinching positions in a lab study. Holding a kickboard out in front keeps the arm overhead and turned in for the whole set.
Sources 33, 5, 4, 34, 24, 28
When a scan helps, and what it can't tell youStrong evidence
Without warning signs, a scan isn't the first step: 93% of elite swimmers' shoulders showed supraspinatus tendinopathy or a tear on ultrasound, unrelated to pain, and rotator cuff changes rise with age whether or not they hurt (from about 10% at 20 or under to 62% at 80 or over, in 6,112 shoulders). A scan report has to match the story.
An ultrasound or magnetic resonance imaging (MRI) scan helps when the arm is weak, especially after an injury, when the shoulder slips out or a labral tear is suspected, or when it isn't improving after about 3 months of good exercise, as our shoulder pain guide says. After a dislocation, X-rays come first.
Sources 35, 36, 37
How it usually goesEmerging evidence
The NHS says shoulder pain usually needs about 2 weeks of looking after before it starts to ease and can take 6 months or longer to recover, and that impingement usually gets better in a few weeks or months. The best-known exercise trial ran for 12 weeks, and a return-to-swim plan for competitive swimmers adds 5 weeks of graded pool work.
Surgery isn't a shortcut. In 16 competitive swimmers, 9 were back to their old level about 4 months after keyhole surgery; after an operation to tighten the capsule, 12 of 15 swam competitively again but only 3 at their old training volume; and after rotator cuff repair, 97% of 31 swimmers aged 47 to 78 swam again, 56% fully. No study has followed recreational swimmers, and no one can promise a date.
Sources 38, 39, 40, 41, 13, 42, 43
