How common it is, and what nobody has countedEmerging evidence
No study counts hip pain in recreational swimmers. The figures come from competitive and masters swimmers. In US college swimming, the hip and groin were 4.8% of men's and 5.9% of women's swimming injuries from 2009 to 2014, and 6.42% of men's and 4.99% of women's from 2014 to 2019, against about 27% to 35% for the shoulder. In 641 college swimmers, groin, hip, pelvis and buttock injuries were 8.5% of their muscle and joint injuries, an estimated 3% of swimmers a year. Among 88 masters swimmers, 5.7% reported hip pain, against 42.0% shoulder and 27.3% lower back pain.
A review of 94 studies (10,973 swimmers) doesn't name the hip among the regions most often injured, and a review of injuries outside the shoulder found only low-certainty risk factors for the pelvis and hip. So this page builds its map from one breaststroke groin survey, lab studies of the kicks and turns, the groin and hip consensus statements, and the conditions each row sends you to; that the kick, the turns and sudden rises in distance are the usual triggers is our reading.
Sources 1, 2, 3, 4, 5, 6, 7
The breaststroke kick and the groinEmerging evidence
In one 2004 survey of 296 competitive swimmers, read as its abstract, 6.92% of breaststroke swimmers had groin pain at the time, against none of the medley swimmers who didn't race pure breaststroke; 42.7% of breaststrokers, 21.5% of medley swimmers and 5.8% of others had been kept off breaststroke training by a groin injury at some point in the past year; and groin injury rose with the amount of breaststroke training.
The kick draws the heels up, turns the feet out and sweeps the legs round and together. The inner thigh muscles were among the most active in it in national-level breaststrokers, a review describes it as needing the hip muscles that pull the legs in and out to work together, and filmed at race pace the hips opened and closed at high speeds. The same kick causes breaststroker's knee, and breaststrokers with frequent knee pain had less inward rotation at the hip.
Sources 8, 9, 10, 11, 12
How wide the knees goEmerging evidence
Elite teenage breaststrokers opened their hips less than amateurs at the start of the glide (36 against 45 degrees), and in 14 swimmers a wider sideways hip swing went with less push from the feet, not more. In an old study of breaststroker's knee, injury rates rose sharply when the hips opened less than 37 or more than 42 degrees at the start of the kick. Swim England teaches knees just a little over hip-width apart, bringing the feet to your bottom rather than the knees to your chest. No study has tested a kick change against groin pain; that a very wide or knees-to-chest kick strains the groin is our reading.
Sources 13, 14, 15, 16
The hip flexors: kick sets, dolphin kicks and turnsEmerging evidence
In front crawl, the flutter kick's force comes through the muscles that bend and straighten the hip. In 8 national-level swimmers, going from 70% to 90% of top speed in the underwater dolphin kick raised activity in the rectus femoris, a hip flexor at the front of the thigh, by about half, and recreational swimmers kept that muscle switched on later in each flutter kick than competitive swimmers. In 32 college swimmers, those with low back pain had a stiffer psoas (the deep hip flexor), arched the lower back more in the dolphin kick and had less hip extension: a link, not a cause.
The flip turn tucks the body by bending at the hips and knees, then pushes off from about 90 degrees of hip and knee bend, with peak forces of roughly 540 to 1,190 newtons in earlier studies. That long kick sets, fast dolphin kicks off every wall and repeated tucks are what flare the front of the hip is our reading: no study links kickboards or flip turns to hip injury.
Sources 10, 17, 18, 19, 20, 21
The hip joint itselfMixed evidence
The hip load figures come from 6 people with hip replacements fitted with sensors, not from healthy swimmers: breaststroke swimming loaded their hips at about 1.6 to 1.9 times body weight, more at higher speeds, and the front crawl kick loaded the hip more than the breaststroke kick (1.79 against 1.18 times body weight at the slower speed tested).
Hip surgeons class breaststroke as an impingement sport, with ice hockey, rowing and water polo. No study has measured hip shape in pool swimmers; in 20 water polo players and artistic swimmers, who tread water with a rotating eggbeater kick, 70% reported hip pain but only 15% had sought care, and 67.5% of hips had a cam shape. Scans of hips without pain often show the same shapes: in a review of 2,114 hips, a cam in 37% (54.8% of athletes) and a pincer in 67%, and a labral tear in 68% in the studies that looked. That is why an impingement diagnosis needs symptoms, examination findings and imaging together.
Sources 22, 23, 24, 25, 26, 27
Who gets itEmerging evidence
In our reading: competitive and masters breaststrokers and medley swimmers; swimmers who suddenly add breaststroke, kick sets, fins, dolphin kicks or flip turns, or build distance quickly at the start of a season; adults learning breaststroke with a wide, knees-to-chest kick; water polo players and artistic swimmers; and swimmers whose dryland training has changed. In one college team, 38% of injuries happened outside practice and competition, for example in strength training, and in another study 13.5% of college swimmers' muscle and joint injuries happened in the weight room.
Serious causes are uncommon. A bone stress injury at the pubic bone has been reported in a swimmer. A lump in the groin that gets bigger when you cough and smaller when you lie down can be a hernia, which needs a GP, and the NHS says a femoral hernia (a small lump at the top of the thigh) needs treating in hospital. The NHS also says hip pain in a child should always be checked. A hot, swollen hip, a painful hernia, a child's limp and pain after a slip on the poolside have their own warning signs.
Sources 8, 25, 28, 4, 29, 30, 31, 32
When a scan or test mattersStrong evidence
Not at first for groin or hip pain that started with the kick or a change in training. The Doha agreement sorts groin pain in athletes by the history and examination: adductor-related pain is tenderness of the inner thigh muscles with pain when you squeeze against resistance, and iliopsoas-related pain is tenderness of the hip flexor, more likely with pain on resisted hip lifting or a hip flexor stretch; inguinal-, pubic- and hip-related pain are separate. A scan helps when the pain doesn't settle with a good exercise programme, when the hip catches or locks, after a pop with a gap in the inner thigh, or when bone pain is suspected, as our hip hub and labral tear guide explain.
Sources 33, 27, 26
How it usually goesEmerging evidence
No study follows hip pain in swimmers. In 641 college swimmers, most groin and hip injuries cost no time or came back within the season: 11 of 16 men's caused no time loss, and 16 of 30 women's missed time but returned that season. In male athletes, sudden adductor strains short of a full tear were pain-free after about 2 weeks and back in full training after about 3, while complete tears took 55 and 78 days. Long-standing adductor pain took 8 to 12 weeks of training in the trial that beat passive care, and hip-related pain needs at least 3 months of exercise first. In one series, swimmers who had keyhole surgery for impingement had cut back or stopped swimming about 6 months before it, and all 26 returned to swimming, at a mean of 3.4 months. No one can promise a date.
Sources 4, 34, 35, 36, 37
