Sitting bends the hip and presses on the area between the legsEmerging evidence
Sitting does two things: it bends the hip, and it presses the buttocks and, on a hard or narrow seat, the area between the legs into the seat. At the front, the hip joint is the commonest cause: hip impingement and labral problems in adults in their 20s to 40s, and arthritis from about 45. In 52 hips of people waiting for impingement surgery (average age 35), sitting made the pain worse in 65%, 43% couldn't sit for more than 30 minutes, and changing position often helped. UK NHS leaflets and hip physiotherapists name low chairs, sitting cross-legged and long car journeys as triggers, because they bend the hip deeply and turn it in.
The inner-thigh muscles (adductors) and the pubic bone are the commonest groin problems in sport: in 207 athletes with long-standing groin pain, the adductors were the main problem in 58%. The agreed definitions of these problems don't mention sitting, and no study has measured sitting pain in them, so "sitting points more to the hip joint" is a reasonable reading, not a proven rule.
Sources 3, 2, 4, 5, 6, 7, 8, 9, 10
Between the legs: a nerve, the pelvic floor, the prostate and the vulvaEmerging evidence
The pudendal nerve supplies the genitals, the perineum and the anus. Pudendal neuralgia, where it is irritated or trapped, causes "sharp, shooting, burning or tingling pain (nerve pain) or numbness", and "The pain may be worse when sitting down and may get worse throughout the day", the NHS says. It's uncommon, more often in women, and linked with pelvic surgery, childbirth, long sitting, cycling and constipation. Specialists describe the pattern as worse sitting, easier standing, lying or on a toilet seat, and not waking you at night. A pelvic floor that doesn't relax (a tight or high-tone pelvic floor) is common in long-lasting pelvic pain: an expert consensus puts it at 60% to 90% of women with chronic pelvic pain.
In men, chronic prostatitis (chronic pelvic pain syndrome) affected about 8 in 100 men in 5 surveys of 10,617; its pain in the perineum, testicles, penis or low tummy "may be exacerbated by prolonged sitting", a US guideline says, and it isn't an ongoing infection. In women, about 16% of 4,915 women in one US survey had had long-lasting vulval pain and 7% had it at the time; the NHS says don't sit in the same position for long. A Bartholin's cyst, a lump beside the vaginal opening, can cause pain "when you walk, sit down, or have sex". Bladder pain syndrome causes pain low in the tummy with needing to pee often.
Sources 11, 12, 13, 14, 15, 83, 16, 17, 18, 19, 20
Is it a hernia?Emerging evidence
The NHS's clue for a hernia is a lump that "may get bigger when you cough, sneeze or cry, and get smaller when you lie down", sometimes with a heavy, dragging feeling or pain. Neither the NHS hernia pages nor the international hernia guideline lists sitting as a sign, and in 323 people with a groin hernia, severe pain was commoner moving (10.2%) than at rest (1.5%). Up to a third of hernias cause no symptoms at all.
Groin hernias are still common: 27% to 43% of men and 3% to 6% of women have one at some point, and femoral hernias are about 4 times commoner in women. So any lump needs a GP, and a femoral hernia needs treating in hospital. Nobody has counted how often people with a hernia feel it when they sit.
Sources 21, 22, 23, 24, 25
The testicles, groin nerves after surgery and the backEmerging evidence
Testicle pain alone "is not usually a sign of testicular cancer", the NHS says, which usually shows as a lump; sudden, severe testicle pain is the 999 sign. A varicocele, a swollen vein in the scrotum that about 15 in 100 men have, aches more after standing for a long time; only a few cause pain.
The nerves of the groin itself can burn from the lower tummy to the inner thigh and the scrotum or labia, usually after an operation: after a bikini-line Caesarean or similar cut, a third of 690 women had long-lasting pain at the scar, and 8.9% pain that limited daily life. No study links these nerves to sitting. The lower back can also cause groin pain: it came with a slipped disc low in the back in 4.1% of 512 people. The tailbone hurts at the base of the spine, not the groin.
Sources 26, 27, 28, 29, 30, 31
What a scan or test shows, and what it doesn'tStrong evidence
For the hip, X-rays come first, and a magnetic resonance imaging (MRI) scan only when more detail is needed, for example before surgery. NICE diagnoses arthritis from 45 without a scan. Scans find things in hips that don't hurt: labral tears in 54% of hips without pain across 29 studies, and a cam-shaped bump (one type of impingement) in 37%. A numbing injection into the hip can help a specialist judge whether the pain comes from inside the joint, though in one series the relief didn't predict how surgery turned out.
Pudendal neuralgia is diagnosed from the story and an examination, with a numbing injection of the nerve as a specialist test; the diagnosis "is essentially clinical", MRI is mainly to rule other things out, and nerve tests are often normal. A hernia is diagnosed by examination, with an ultrasound scan if it's unclear. A urine test matters for burning when you pee or a fever.
Sources 6, 7, 32, 33, 34, 14, 35, 36, 12, 23, 37, 38, 39
How it usually goesEmerging evidence
NHS inform expects new hip pain to begin to settle within 6 weeks, and an Oxford NHS impingement booklet says physiotherapy takes "three to six months" to show its full effect. Over 10 years, 76% of 495 people with suspected early hip arthritis had pain that stayed the same or eased. Long-standing adductor pain improved over 8 to 12 weeks of active training in most athletes in one trial.
About a third of men with chronic prostatitis were better within a year. Pudendal neuralgia can last a long time, though after childbirth it usually settles over months, and the NHS says "there are treatments that can help". Pain after a hernia repair usually eases over time. No one can promise a date.
Sources 40, 2, 41, 42, 15, 12, 23, 11
