In sport, the thigh musclesEmerging evidence
In 2,299 professional footballers followed for several seasons, muscle injuries were 31% of all injuries that stopped them playing, and the hamstrings (37%), the inner thigh muscles (23%) and the quadriceps (19%) were three of the four biggest groups; 16% were reinjuries, which kept players out longer. In another elite cohort, thigh muscle injuries were 25% of all injuries: 88% were strains and 12% bruises from a direct blow, and players came back from the bruises in under half the time.
Most people with thigh pain aren't professional footballers, and these numbers come from elite men. NHS inform says thigh problems come from overstretching or twisting, a fall, a direct blow, or no clear reason, and usually begin to settle within 6 weeks.
Sources 1, 2, 3
A sudden pull: a quad or hamstring strainStrong evidence
A strain often comes with a popping or snapping feeling and sudden pain, then tenderness and bruising, which can spread down to the calf and ankle over 1 to 2 days, the American Academy of Orthopaedic Surgeons (AAOS) says. At the back of the thigh, the NHS describes a sharp pain, sometimes a snap or pop, then tenderness, swelling and bruising, and difficulty standing or walking.
The AAOS warns that a hamstring pulled off the sitting bone can look like a strain, with similar bruising, but can be time-sensitive and may need surgery, so pain close to the sitting bone after a pop needs checking. Our quad strain and hamstring strain guides cover both in full.
Sources 4, 5
A knock: a dead leg, and bone in the muscleEmerging evidence
A dead leg is a bruise deep in the thigh muscle (a contusion) from a knock. In 117 thigh bruises in military cadets, people were out of activity for a mean of 13 days when the knee could still bend past 90 degrees, 19 days for moderate and 21 days for severe bruises. Bone formed in the muscle (myositis ossificans) in 9%, more often with knee bend under 120 degrees, a bruise from football, a previous thigh injury, a delay of more than 3 days before treatment, or a swollen knee. In one small series of 47 midshipmen, with no comparison group, the knee was held bent to 120 degrees for the first 24 hours, and they returned to full activity in a mean of 3.5 days.
The AAOS says the two main complications of a deep bruise are bone forming in the muscle and compartment syndrome, a build-up of pressure inside the muscle that the NHS says needs surgery as soon as possible. In 8 people who developed it after a bruise or tear at the front of the thigh, the pressure in the muscle was 41 to 80 millimetres of mercury, and all had normal function about 4 weeks after an operation to release it.
Sources 6, 7, 8, 2, 9, 10, 11
Pain from somewhere else: the hip joint, the back and a skin nerveEmerging evidence
The hip joint is often felt in the thigh. In 51 people with a painful hip joint, mapped before a hip injection, 57% felt it in the thigh, 55% in the groin and 71% in the buttock. The NHS lists hip osteoarthritis (over 45, pain worse walking, stiffness after moving) and bursitis, whose pain may spread to the thigh, among the causes of hip pain.
NHS inform says problems felt in the thigh can come from the back, even when the back doesn't hurt, described as pins and needles, or sharp, hot or burning pain. A burning, tingling or numb patch on the outer thigh is usually meralgia paraesthetica, a squeezed skin nerve; the AAOS says tight clothing and weight gain are two of the commonest causes, along with a heavy tool belt.
Sources 12, 13, 3, 14
A deep ache in the thigh boneEmerging evidence
In 914 college athletes followed for 2 years, 7 of 34 stress fractures (20.6%) were in the shaft of the thigh bone, more than the authors expected. A small series of 7 top athletes says these fractures have few clear signs, so diagnosis is often delayed. Stress injuries of the neck of the thigh bone, near the hip, had the longest return to sport after the navicular in the foot (107 days) and among the highest complication rates in pooled studies, which is why a runner's groin or thigh pain with every step needs checking the same day.
Separately, bisphosphonates, the bone medicines taken for osteoporosis, can rarely cause an unusual fracture of the thigh bone after little or no injury, mainly after long-term use. The UK medicines regulator (MHRA) says some people have a dull ache in the thigh or groin for weeks to months before, that it often affects both sides, and that people taking these medicines should report thigh, hip or groin pain; the NHS alendronic acid page says call a doctor or NHS 111 straight away.
Sources 15, 16, 17, 18, 19
Clots, arteries, children and other causesStrong evidence
The NHS's signs of a blood clot in a deep vein (a deep vein thrombosis, DVT) are throbbing pain in one leg, usually in the calf or thigh, swelling, red, blue or darkened skin around the painful area, and swollen veins. An ache in the leg on walking that goes after a few minutes' rest can be narrowed arteries; NHS Scotland's pathway says it is felt in the thigh and buttock when the narrowing is higher up.
In children, the NHS says hip problems can be felt in the thigh or knee, so sudden thigh pain or a limp needs an urgent GP appointment or NHS 111; aching in both legs in the evening that has gone by morning is usually growing pains. Polymyalgia rheumatica causes pain and stiffness around the shoulders, neck and hips, with morning stiffness lasting more than 45 minutes, mostly over 65. Bone pain that is worse at night, or a lump, needs a GP: rarely, it is a bone tumour.
Sources 20, 21, 22, 23, 24, 25, 26
When a scan or test helpsStrong evidence
Strains are usually diagnosed by examination, with a magnetic resonance imaging (MRI) scan if the muscles and tendons need a closer look. A hard lump weeks after a knock can be X-rayed for bone forming in the muscle: in the midshipmen series, X-rays at 3 and 6 months found it in 1 of the first 23.
For a suspected stress fracture, an early X-ray may look normal, and an MRI shows the bone swelling; a clinical test helped early diagnosis in the college athletes. The MHRA asks doctors to check anyone taking a bisphosphonate who has thigh, hip or groin pain for an incomplete fracture, and to check the other thigh bone too. Meralgia paraesthetica is diagnosed by pressing on the nerve to bring on the burning, sometimes with a numbing injection to confirm it. A swollen, throbbing leg needs an ultrasound scan within 24 hours if a doctor thinks it's a clot, and narrowed arteries are checked by comparing blood pressure at the arm and ankle.
Sources 4, 8, 27, 15, 18, 14, 20, 21
How it usually goesEmerging evidence
NHS inform expects most new thigh problems to begin to settle within 6 weeks. The NHS says mild hamstring injuries usually get better in a few days and severe ones can take weeks or months, and the AAOS says getting strength and flexibility back takes 10 days to 3 weeks for a mild thigh strain and up to 6 months for a severe one. Most sprains and strains feel better after 2 weeks. In elite football, 16% of muscle injuries were reinjuries.
In the 7 athletes with a stress fracture of the thigh bone, all were back to full activity 12 to 18 weeks after starting a four-phase plan, with no recurrence over 4 to 8 years. The burning of meralgia paraesthetica can take time to stop, and some numbness can stay, the AAOS says. Of people with narrowed leg arteries, 75% stay the same or improve. No one can promise a date.
Sources 3, 5, 4, 28, 1, 16, 14, 22
