Why bending shows up hip pain, and what no study has countedEmerging evidence
Bending forward folds the hip, and the lower back bends with it, so a stiff or pinching hip and a sore back both show up when you bend. A hip with arthritis loses some of its bend, and a hip with an impingement shape pinches as it bends and turns inwards. No study counts which causes hip pain when bending over, so this guide's map is built from what each condition is known to do, pain-mapping studies and health-service pages, and says so.
Hip pain is common, and mostly not arthritis on an X-ray: in a US community study of 3,068 people aged 45 and over, 36% reported hip pain, aching or stiffness on most days, but 9.7% had hip arthritis that caused symptoms and showed on an X-ray.
Sources 1, 2, 3, 4, 5, 6
How far reaching your feet bends the hip: the numbers disagreeEmerging evidence
Socks, shoes and toenails ask for one of the deepest hip bends most people make each day, but the measured angle depends on the method. With a wearable sensor on 30 healthy people, tying shoes took about 126 degrees of hip bending and squatting about 120. With skin markers on 26 healthy young adults sitting down, tying laces or picking something up beside the foot took about 90 degrees. The two methods measure the hip differently, so their numbers disagree, and neither tested people with hip pain.
What they agree on is that reaching your feet is a deep bend, so a stiff or pinching hip shows up there first. In 51 people waiting for impingement surgery, hip bending was limited to about 97 degrees on average, and 31% found shoes and socks difficult.
Sources 1, 2, 7
The hip joint: impingement, labral tears and arthritisEmerging evidence
In hip impingement (femoroacetabular impingement, FAI), the shape of the ball or the socket makes them meet as the hip bends and turns inwards; an international consensus defines it by symptoms, examination and imaging together. In 51 people waiting for surgery (average age 35), 83% had groin pain, 65% said sitting made it worse and 88% hurt on the impingement test. Clicking, catching or locking deep in the groin can come from a tear in the rim of the socket (the labrum), often alongside impingement.
From mid-life, a stiff ache in the groin, the front of the thigh or the buttock points more to arthritis. The NHS says you may find it difficult to put your shoes and socks on, and Arthritis UK says pain when you put on your socks "is often a sign of a hip problem". The National Institute for Health and Care Excellence (NICE) diagnoses osteoarthritis from 45 without a scan when the pain comes with activity and morning stiffness lasts 30 minutes or less.
Sources 8, 4, 7, 9, 3, 10
Hip or back? Where it hurts sorts themEmerging evidence
The hip and the back are easily confused. In 97 people at one clinic, a limp or groin pain made a hip problem about 7 times as likely, and stiff inward turning of the hip about 14 times. Pain from the hip joint, confirmed by an injection, was felt in the buttock in 71% of 51 people, the thigh in 57%, the groin in 55% and below the knee in 22%; pain from the SI joint was felt in the buttock in 94% of 50 people and the groin in 14%. Arthritis UK says knee pain is sometimes the only sign of a hip problem.
Pain across the low back, eased by walking, points to the back, which the NHS says usually improves within a few weeks. Pain at the sit bone when you bend with straight legs fits the hamstring tendon, which deep hip bending presses against the bone. Outer hip pain at the bony point mostly affects women in mid-life and is worse lying on that side and crossing the legs; bending forward isn't its usual trigger. Groin pain in sport has its own types (adductor, hip flexor, lower tummy wall and pubic bone), and the consensus that names them doesn't list bending as a trigger. A physiotherapist tells the hip from the back by testing both.
Sources 11, 12, 13, 9, 5, 14, 15, 16
Causes that need other care are uncommonStrong evidence
A broken hip after a fall, cauda equina syndrome (pressure on the nerves at the bottom of the spine, with numbness around the genitals or bottom and bladder or bowel changes), a joint infection, a child's hip problem and a dislocated hip replacement are rare, but they need help quickly, and the warning signs give the NHS's tiers. A child or teenager with hip, thigh or knee pain and a limp needs checking the same day, because hip problems can be felt in the thigh or knee.
A lump in the groin or at the top of the thigh that grows when you cough, strain or bend can be a hernia; femoral hernias, mainly in women over 50, can become tightly squeezed (strangulated). After a hip replacement, the NHS says contact your GP or care team if you're worried, and an NHS trust leaflet lists unusual hip movement or a change in shape as needing immediate attention. Avascular necrosis, where part of the ball of the hip loses its blood supply, is linked with high-dose steroids, heavy drinking, sickle cell disease and lupus, and Arthritis UK says it needs an urgent magnetic resonance imaging (MRI) scan, because an early X-ray can miss it.
Sources 17, 5, 18, 19, 20, 22, 21, 23, 24, 9
What a scan shows, and what it doesn'tStrong evidence
NICE diagnoses osteoarthritis from 45 without imaging when the symptoms are typical, and doesn't routinely offer imaging for low back pain. Scans of hips that don't hurt often show what people are told is wrong: a cam shape in 37% and a pincer shape in 67% of 2,114 hips across 26 studies, labral tears in 69% of 45 volunteers, and labral tears in 54% of people without hip pain against 62% with it across 29 studies.
Examination tests rule things out better than they rule them in. The impingement test (bending the hip, then bringing it across and turning it in) is positive in nearly everyone with impingement but in many people without it, and clusters of SI joint tests are more useful when they are negative than when they are positive. A scan matters after a fall, with a warning sign, for suspected avascular necrosis, and when surgery is being discussed after a good 3 months of exercise-based treatment.
Sources 10, 25, 26, 27, 28, 29, 30, 31
How it usually goesEmerging evidence
In 139 people with hip complaints in Dutch general practice, 24% had recovered at 3 months and 37% at 12 months, with a better outlook for shorter, first episodes. Of 224 people aged 50 and over with new hip pain, 12% had a hip replacement within 3 years and 22% within 6, so most didn't. In 495 people with suspected early hip arthritis, 76% had stable or falling pain over 10 years, though 37% had clear ups and downs.
Teenagers with impingement managed without surgery improved over 5 years, and new back pain fell on average from 52 to 23 out of 100 in its first 6 weeks across 33 groups of people. No one can promise a date.
Sources 32, 33, 34, 35, 36
