How common knee injuries are on the snowStrong evidence
Ski injury rates are counted in very different ways, so they vary: about 1.9 injuries per 1,000 skier days across 43 studies of amateurs and 3.8 for amateur alpine skiing, with very large differences between studies, and 2.24 per 1,000 skier days at 29 western Canadian resorts from 2008 to 2018, where skiers most often hurt a knee and snowboarders a wrist. Across studies the knee is about 27% to 41% of ski injuries, and it was almost a third of skiers' injuries at Finland's largest resort. By our arithmetic, at 2 to 4 injuries per 1,000 skier days, that is roughly one injury of any kind for every 40 to 80 six-day trips.
The commonest single ski injury is a torn ACL. Over 18 Vermont seasons ACL sprains were 17.2% of skiing injuries, about 1 in 6, against 1.7% of snowboarding injuries, and a review by the Vermont ski safety group puts ACL tears at about 0.23 per 1,000 skier days.
Sources 1, 2, 3, 4, 5
Bindings protect the shin, not the kneeStrong evidence
Bindings that release cut injuries below the knee by almost 90% from the early 1970s, while serious knee sprains rose sharply from the late 1970s; a review concluded that modern bindings have not protected the knee from serious ligament injury. In Vermont, the overall injury rate fell 55% over 34 years to 2006, and ACL sprains fell 42% over the last 14 of them. Before short, shaped carving skis the MCL was the commonest knee injury; now the ACL is, and over 18 Vermont seasons skiers' MCL sprains became less common.
Sources 6, 7, 8, 5
How the knee gets hurtEmerging evidence
The ski is a long lever on the leg, and the boot holds the ankle, so a fall that twists the ski twists the knee. The Vermont group describes three ways the ACL tears without a collision. In the forward twisting fall, the inside edge of the front of the ski catches and the knee is pushed inwards and twisted outwards: it was the commonest fall in 541 recreational skiers who picked the picture closest to their injury (32.9%), caused 54% of tears in 220 Austrian carving skiers, and was the commonest fall in 282 skiers whose knee injuries needed hospital care. In the phantom foot, the skier is off balance backwards with the hips below the knees and all the weight on the inside edge of the tail of the downhill ski (22.5% in the recall survey, commonest at ages 30 to 40). In the boot-induced injury, a jump lands on the tails with the leg straight and the back of the boot drives the shin forwards (7.8%).
The knee forced straight past its range (19.0% in the survey) and collisions (about 2%) account for others. In the 282 hospital cases, every injury involved the ACL and about two-thirds had other damage too: of those, half had an MCL injury and 40% an inner meniscus injury. In World Cup racers, half of 20 filmed ACL tears were a slip-catch, the outer ski catching its inside edge during a turn rather than in a fall; that is elite racing, another group.
Sources 1, 9, 10, 8, 11
Telling the injuries apartEmerging evidence
The NHS lists a knee that is unstable, gives way when you try to stand, won't straighten or popped at the time of injury under a torn ligament, tendon or meniscus. An ACL tear usually brings a pop, swelling within about a day and a knee that later gives way. An MCL sprain hurts on the inside, particularly with twisting movements, an NHS trust says. The NHS says a meniscus tear usually happens when you twist your knee playing sport, and its swelling may not start for a few hours or days. Kneecap pain builds with load rather than starting with a fall, and is worse squatting, on stairs and after long sits. Injuries often come together after a fall, which is why a clinician examines the knee.
Sources 12, 13, 14, 15, 16, 17
Who gets hurtStrong evidence
In 3,277 injured and 2,992 uninjured Norwegian skiers and snowboarders, knee injuries were commoner in alpine skiers than snowboarders (odds ratio 1.82), in women (1.67) and in beginners (3.13). Across 27 studies of first ACL tears in skiers, being female, taking risks, lower skill, older age, worn boot soles and bindings that didn't release all went with injury. Austrian data put women's ACL risk at about 3 times men's, and of 17,914 injured Austrian skiers, 29.5% of the men and 53.0% of the women had hurt a knee.
In 392 ACL-injured skiers and 392 matched uninjured skiers, fresh, grippy or icy snow, cold and easy slopes all went with ACL injury. These are associations recalled after the event, and easy slopes are where less skilled skiers ski.
Sources 18, 19, 10, 20, 21
Kneecap and tendon pain without a fallEmerging evidence
Nobody has counted front-of-knee pain in recreational skiers. In 108 Swiss racers aged 13 to 15, 47.2% had an overuse knee complaint in a year, mostly at the patellar tendon below the kneecap; in 47 young racers followed for 4 years, patellar tendon complaints fell from 29.8% to 12.8%; and in 26 elite women, knee overuse complaints went with previous serious knee injuries and more training hours. Those are racers, another group. Deep knee bends under load press the kneecap hardest, in a lab study.
In our reading, a sore knee without a fall is likeliest in skiers with past knee injuries, kneecap pain or arthritis, on the first days of a trip after months off, and in a deep, back-seat stance.
Sources 22, 23, 24, 25
Bindings and bootsEmerging evidence
Most ACL-injured skiers say the binding didn't release: 78% of 498 Austrian skiers, more often women (83% against 66%), and bindings released in only 19.3% of adults in the American recall survey. That is self-report with no comparison group, and the Vermont review authors say advances in bindings weren't designed to protect the knee from sprains. A binding releases under the twisting and forward forces that break the shin; the knee usually tears in falls where the forces on the binding are too small or in the wrong direction (our reading of the Vermont reviews).
Whether women would benefit from lower settings is an open question. The standard for setting bindings allows a 15% lower setting on request, and in a lab study 13 of 20 young women could release their bindings at least once with both legs at the lower setting, against 3 at their usual setting, with no injury outcome; women on carving skis without newly adjusted bindings had more knee injuries than those with newly adjusted ones. The Vermont group advises a check by a qualified ski shop at least once a season, and the American Academy of Orthopaedic Surgeons (AAOS) advises bindings set and tested by a shop that follows recognised standards. Worn boot soles went with ACL injury.
Sources 26, 9, 1, 27, 28, 20, 7, 29, 19
Tiredness, the first days and the last runMixed evidence
The idea that injuries come on the last run, when you're tired, is popular, and an orthopaedic page repeats it. The evidence is thin either way. One questionnaire of 588 Austrian skiers with a torn ACL, read as its abstract and with no comparison group of uninjured skiers, found that about 81% felt no or only a trace of leg fatigue when they were hurt, about a third were hurt on the first day of the trip and about 57% within the first two days, and more women than men were hurt in their first hour of skiing (28% against 17%). At an Italian trauma centre, 5.7% of injured skiers blamed tiredness.
The thighs do tire. In 24 fit recreational skiers, 4 hours of skiing cut the thighs' lowering strength, still reduced 24 hours later, and in 38 women over 40, thigh fatigue built through the morning and a 45-minute lunch break didn't restore it. So for a sore knee, tired thighs over several days add load, and the first days deserve as much care as the last run (our reading).
Sources 29, 30, 31, 32, 33
When a scan or test mattersStrong evidence
After a fall, clinicians use the Ottawa knee rule to decide on an X-ray: age 55 or over, tenderness at the head of the fibula (the bony bump on the outer side just below the knee) or only at the kneecap, being unable to bend the knee to 90 degrees, or being unable to take four steps. It picked up 98.5% of fractures across 6 studies of 4,249 adults. A torn ACL is diagnosed by examination, often more easily a few weeks after the injury; a magnetic resonance imaging (MRI) scan shows damage to the meniscus, cartilage and other ligaments, which matters when surgery is being considered (our ACL injury guide).
Meniscus tears are common on MRI in knees that don't hurt: from 19% of women in their 50s to 56% of men aged 70 to 90 had one. A child's fast-swelling knee injury needs an X-ray first, because a growth plate can be injured instead of the ligament (our twisting knee guide). Kneecap pain needs no scan.
Sources 34, 35
How it usually goesEmerging evidence
An MCL sprain usually takes around 6 to 12 weeks to heal, an NHS trust says. In 121 young, active adults with a fresh ACL tear, rehab with surgery only if needed gave the same knee scores at 5 years as early reconstruction, and 51% of the rehab-first group had a reconstruction by then; the NHS says not all ACL injuries need surgery, and that it can take up to a year to play sport again after an operation. The NHS says a meniscus tear can get better on its own, but it can take a while.
Knee injuries matter for later: after an ACL injury the odds of knee osteoarthritis were about 4 times those of an uninjured knee, and about 6 times after a meniscus injury. No one can promise a date, which is why the plan builds strength while skiing comes back.
Sources 15, 36, 37, 38, 16, 39
