Kneecap pain: the commonest problem in young, active womenEmerging evidence
Kneecap pain (patellofemoral pain) is an ache around or behind the kneecap, worse on stairs, squatting, running, jumping and long sits with the knees bent. It can come on slowly or suddenly, and it can come back and last for years. In 23 studies, 22.7% of the general population and 28.9% of adolescents had it each year, and at any one time 22.7% of girls in sport had it, against 7.2% of adolescents overall.
At the US Naval Academy, women were 2.23 times as likely as men to develop kneecap pain in 1,525 cadets followed for up to 2.5 years, though about as many women as men had it when they arrived. Those were military cadets, not the general public.
Sources 1, 2, 3
It isn't wide hipsStrong evidence
In 18 prospective studies of 4,818 people, the Q angle (the angle from the hip to the kneecap), height, weight and body fat didn't predict who developed kneecap pain, while weak thigh muscles did in military recruits. In 69 people, men's and women's Q angles differed by only 2.3° on average, and men and women of the same height had similar Q angles: the difference follows height, not a wider pelvis.
Snapshot studies did find a slightly larger Q angle and weaker hip and thigh muscles in people who already had kneecap pain, but a snapshot can't show which came first. Thigh and hip strength can be trained; the shape of your pelvis can't, and doesn't need to be.
Sources 4, 5, 6
ACL injuries are commoner in female athletesStrong evidence
Across 58 studies, about 1 in 29 female athletes and 1 in 50 male athletes tore an ACL over follow-ups from a season to 25 years, about 1.5 to 1.7 times the risk. The gap is largest in basketball (about 3.5 times) and football (about 2.7 times), and close to even in alpine skiing. Most tears happen without contact, in a landing, a cut or a sudden stop.
Sources 7, 8
Hormones, the menstrual cycle and the pillMixed evidence
Across 21 studies of 68,758 people, knee ligaments were looser around ovulation than early in the cycle, ACL injuries were least common in the second half of the cycle in 4 of 5 studies of women not using hormonal contraception, and the 2 largest studies suggested hormonal contraception might lower the risk by up to about 20%. The review rates its own evidence as low quality. Joints do loosen in pregnancy, but that didn't track hormone levels in another study. None of this is a reason to avoid sport on certain days.
Sources 9, 10
Knee arthritis and the menopauseStrong evidence
Osteoarthritis is commoner in women, the NHS says. In a meta-analysis, men had about a third less knee osteoarthritis than women, and women's was more severe, particularly after menopausal age; worldwide in 2020, about 8,060 per 100,000 women and 5,780 per 100,000 men had osteoarthritis. The National Institute for Health and Care Excellence (NICE) diagnoses it without a scan from 45 when joint pain comes with activity and morning stiffness lasts 30 minutes or less.
The NHS and NICE list muscle aches and joint pains among menopause symptoms, and across 16 studies 71% of perimenopausal women reported muscle and joint pain, more than before the menopause. Reviews now describe a musculoskeletal syndrome of menopause, but the menopause also arrives at the age when osteoarthritis becomes common, so the two overlap.
Sources 11, 12, 13, 14, 15, 16, 17, 18, 19
Loose joints, and kneecaps that slipMixed evidence
Of 6,021 people diagnosed with joint hypermobility syndrome or Ehlers-Danlos syndromes in Wales, 70% were women, diagnosed on average 8.5 years later than men. The NHS says the main treatment is building muscle strength and fitness, starting with low-impact exercise, and not overextending your joints just because you can.
A first kneecap dislocation is commonest at 14 to 18. In one 21-year population study it was about as common in girls as boys, but in a clinic cohort of 189 people the risk was highest in girls of 10 to 17, so the studies disagree.
Sources 20, 21, 22, 23
Pregnancy, periods and runningEmerging evidence
Leg and foot pain was commoner in 107 women who had just given birth than in 91 who hadn't (56% against 37%), mostly starting in mid to late pregnancy, which the authors put down to load rather than hormones. The NHS recommends 150 minutes of activity a week in pregnancy, including strength work, but not starting a new vigorous activity such as running.
Period cramps can spread to the back and thighs, and women with painful periods are more sensitive to pain generally, but no study we found shows periods cause knee joint pain. Running injuries were about as common in women as in men across 31 studies, with more bone stress injuries in women, and in 2,002 injured runners, kneecap pain was the commonest injury in both sexes.
Sources 24, 25, 26, 27, 28, 29, 30
When a scan or test helpsStrong evidence
Most knee pain doesn't need a scan: kneecap pain is diagnosed by examination, with pain on squatting the main sign, and NICE diagnoses osteoarthritis without imaging from 45 when the symptoms fit.
Tests answer specific questions: an X-ray after a dislocated kneecap, which the NHS says you will usually need, or when a fracture is possible; a magnetic resonance imaging (MRI) scan after a suspected ACL tear, to check the cartilage and meniscus; an ultrasound scan within 24 hours for a suspected clot; urgent tests, including fluid drawn from the joint, for a suspected joint infection; and blood tests when inflammatory arthritis is suspected.
Sources 1, 14, 31, 32, 33, 34
How it usually goesEmerging evidence
In 40 young women with kneecap pain, 85% were back to sport without pain a year after a 12-week programme, though there was no untreated group to compare, and kneecap pain can come back and last for years. Knee arthritis changes slowly, and exercise improves pain and function, though NICE warns that pain may rise at first. Menopause symptoms usually last 7 to 9 years, and joint pain can continue afterwards. An ACL tear or a dislocation means months of rehab, with or without surgery. No one can promise a timescale.
Sources 35, 1, 36, 14, 15
