Usually soreness, after lunges, squats, sprints and new classesStrong evidence
Delayed onset muscle soreness (DOMS) follows new or harder exercise, especially work that lowers a weight or your body slowly (eccentric work). It typically starts 12 to 24 hours after the session, is worst between 24 and 72 hours and is gone within 5 to 7 days, and it is commonest at the start of a season, after a break and with new activities.
The hip's big muscles, the glutes, the adductors on the inside of the thigh, the hip flexors at the front and the hamstrings at the back, all work while they lengthen in lunges, split squats, deep and wide squats, hip thrusts, sprints and downhill running, which is the kind of work that leaves muscles sore 1 to 3 days later.
Sources 1, 2
A strain is the commonest injury: the groin and the hip flexorsEmerging evidence
The NHS links pain, swelling or bruising after intense or repetitive exercise with a sprain, strain or tendonitis. A strain starts at one moment, often in a kick, a sprint, a change of direction, a slip into a wide stance or the bottom of a deep lunge, with pain, tenderness or weakness, sometimes swelling, bruising or spasm; not warming up, tired muscles and sport are common causes, the NHS says.
In 110 male athletes seen within a week of an acute groin injury, two-thirds were adductor injuries, mainly the adductor longus; kicking was the commonest way it happened in football (40%) and changing direction in other sports (31%). On magnetic resonance imaging (MRI) scans, a third of acute groin injuries were in the hip flexors: the rectus femoris mostly with kicking and sprinting, the iliacus and psoas mostly with changes of direction. These were male athletes at one sports hospital, not gym-goers. An international agreement on groin pain in athletes sorts it into adductor-, iliopsoas-, inguinal- and pubic-related groin pain, plus the hip joint, from the history and examination.
Sources 3, 4, 5, 6, 7
Tendons that complain after a change in trainingEmerging evidence
The outer hip (gluteal) tendons can become painful after hills, stairs, step classes, a jump in mileage or lots of single-leg and side-lying work; this is commonest in mid-life and in women. A review describes squeezing the tendon against the bone while it is loaded, and positions that bring the thigh across the body, such as crossing your legs, as most damaging, and an NHS trust adds that repeated stretching can irritate it. The review doesn't name a sudden change in load, so "a load the tendon isn't used to" is our reading.
Sources 8, 9
A pinch at the bottom of a squat, impingement and labral tearsStrong evidence
Hip shape varies a lot, and scan findings are common in hips that don't hurt. Impingement (cam) shapes were found in 37% of 2,114 pain-free hips (54.8% in athletes, 23.1% in the general population), labral tears on MRI in 69% of 45 volunteers aged 15 to 66 with no hip pain, and labral tears in 54% of people without hip pain across 29 studies.
Femoroacetabular impingement (FAI) syndrome is diagnosed only when symptoms, examination and imaging all fit, an international agreement says. People with cam shapes couldn't squat as deep as matched controls in a small lab study, and a clinical review notes that up to a quarter of people with impingement squat deeply without pain. So a pinch at the front of the hip at the bottom of a squat is usually where your hip runs out of bend, not damage.
Sources 10, 11, 12, 13, 14, 15
Bone: a stress fracture of the hip in runnersEmerging evidence
A stress fracture of the neck of the thigh bone (femoral neck) is uncommon, about 3% of athletes' stress fractures, and commonest in distance runners and in women. The pain comes on gradually at the front of the groin (87% in one series), can spread to the thigh or knee, follows a recent rise in training, and later comes at rest and at night. It is the one cause in this guide that mustn't be trained through, because a fracture that displaces can cut off the blood supply to the top of the thigh bone.
Bone stress injuries often follow a rapid increase in activity, 3 to 4 weeks into a new routine, and low energy intake, too little sleep and no rest days add to the risk. In college track and field athletes, women whose periods had become irregular or stopped had more severe injuries, and femoral neck injuries took longer to return from. Treated early, most heal well: 71% returned to full activity in reported cases.
Sources 16, 17, 18, 19
How common, in lifters and runnersEmerging evidence
The hip and groin are a minority of running injuries: 7.0% by prevalence and 11.3% by incidence across studies with very different definitions. In 104 Swedish powerlifters, 70% were carrying an injury that affected training, with the low back and pelvis, the shoulder and the hip commonest, but only 16% had to stop training completely. No study we found gives a rate of hip soreness or strain in ordinary gym-goers or class members.
In 874 novice runners, weekly distance jumps of more than 30% over 2 weeks went with more overuse injuries in an exploratory analysis, yet in a trial of 532 novice runners, a programme built on the 10% rule didn't reduce injuries (20.8% against 20.3%). Build up gradually, but treat any exact rule as a guess.
Sources 20, 21, 22, 23
Hernias, infections, teenagers and muscle breakdown: the causes not to missStrong evidence
A hernia is a lump that may get bigger when you cough or strain and smaller when you lie down; the NHS asks you to see a GP if you think you have one. Femoral hernias, mainly in women over 50, need treatment in hospital, and with very bad tummy pain or sickness they are an emergency. An inguinal hernia, a lump where the leg joins the tummy, may need planned surgery if it causes symptoms such as pain, and may not need treatment if it doesn't. A joint infection brings sudden severe pain in one joint and hot, swollen or red skin, usually with a fever, although not everyone has one.
In teenagers, a sudden pull can tear a piece of growth plate off the front of the pelvis (an avulsion fracture), mostly during sport; across 852 fractures, the average age was 14, 79% were boys, and 86.6% were treated without surgery. Muscle breakdown (rhabdomyolysis) after a big, unaccustomed session is rare but can harm the kidneys; published cases include a first spin class, a workout of 100 back squats and intervals of wall sits, squats, lunges and jumps, and about a quarter of people admitted after spin classes had no dark urine.
Sources 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34
When a scan or test helpsStrong evidence
Soreness, strains and tendon pain are recognised from the story and an examination. Scan findings are common in active people without pain, and an international consensus says imaging must be read alongside the history and examination, with an X-ray or ultrasound first and MRI second.
Tests answer specific questions: an urgent X-ray, then MRI, for a suspected stress fracture; an ultrasound for a suspected hernia, or for a groin strain when it would change the plan; a same-day X-ray for a teenager's suspected avulsion fracture; an X-ray of hip shape, sometimes with MRI, when hip-related pain hasn't settled after about 3 months of exercise and surgery is being discussed; blood and urine tests for suspected muscle breakdown; and fluid drawn from the joint for a suspected infection.
Sources 35, 16, 36, 13, 34, 27
How it usually goesEmerging evidence
Soreness is gone within 5 to 7 days. The NHS says most strains feel better after 2 weeks, and suggests avoiding strenuous exercise such as running for up to 8 weeks. In 81 male athletes with criteria-based rehab, mild to moderate adductor strains were pain-free in a median of 13 days and back to full team training in 18; complete tears took 78 days.
Long-standing groin pain improved over the 8 to 12 weeks of the trial that worked; hip-related pain from impingement or a labral tear gets at least 3 months of exercise first; outer hip tendon pain can take 6 to 12 months with exercise therapy, an NHS trust says; and new hip pain usually begins to settle within 6 weeks, NHS inform says. A stress fracture of the hip means weeks on crutches, and sometimes surgery. No one can promise a timescale.
Sources 1, 4, 37, 38, 36, 9, 39, 16, 19
