How common it is: blisters leadStrong evidence
Feet are the commonest trouble spot on long walks. On the Appalachian Trail, 64% of 280 long-distance hikers had blisters, the commonest complaint; on the John Muir Trail, 57% of 771 backpackers had them; and on the Camino de Santiago, 74% of 315 walkers had a blister, most often under the ball of the foot or on the little toe. Across 7 studies of 17,757 injured hikers, blisters made up 8% to 33% of injuries, and ankle sprains were common. In New Zealand club hikers carrying packs up to 29% of body weight, 74% reported injuries, with sprains the commonest type and knees, ankles and feet the commonest places.
In soldiers on long, heavily loaded marches, blisters made up 48% of injuries and foot pain 18%, and military reviews list blisters, stress fractures, pain in the ball of the foot and numb toes among load carriage injuries. These figures come from soldiers, not hikers, and soldiers carry far more for longer, so they are an upper bound.
Sources 1, 2, 3, 4, 5, 6, 7, 8
How blisters form, and why they matterEmerging evidence
Blisters come from shear: the skin is pulled one way while the deeper layers stay put, thousands of times a day. They form more easily on moist skin, as NHS inform says, and in 86 long-distance hikers wetter skin went with blisters. In 203 Camino walkers, hiking in wet socks went with nearly twice the risk (1.94 times), while the fibre the socks were made of made no difference, and walking on tarmac raised the risk while dirt paths lowered it.
Blisters come early: in multi-day races, 89% appeared by day 2. They matter: in 298 Camino walkers, blisters under the ball of the foot caused the most pain and limited walking most, and on a 580 km student march over 21 days, every injured walker had blisters and 18.3% developed a skin infection (cellulitis). Common doesn't mean harmless or inevitable.
Sources 9, 10, 11, 12, 3, 13, 14, 15
How the causes are told apartEmerging evidence
Hot spots and blisters on the heel, toes or ball of the foot are friction blisters, which the NHS says often heal on their own within a week. Pain under the heel that is sharp on your first steps in the morning, easing as you walk, is plantar heel pain (which NHS inform now calls plantar fasciopathy); the NHS lists doing a lot more walking than usual among its causes. The back of the heel, stiff at the start and worse uphill, is the Achilles tendon: in 16 cadets carrying 20 kg, the load on the Achilles rose sharply. An ache under the ball of the foot is metatarsalgia, and burning, shooting or numbness between the 3rd and 4th toes, worse in tight footwear, is often Morton's neuroma. Numb or tingling toes after long loaded walks can also be pressure on the small nerves of the toes, which reviews of soldiers describe.
Sore, bruised or numb toes, or a toenail that goes black after long descents, are the toes hitting the front of the boot in our reading, untested in hikers; the NHS says nails can change colour and fall off after an injury, and advises against footwear that pinches your toes. Pain across the top of the foot under the laces is usually irritated tendons or lace pressure: in runners, lace pressure peaked over the bones and tendons there, and the NHS says top of foot pain can come from shoes that are too tight and usually gets better in a few weeks. A rolled ankle with swelling on the outside is a sprain, one of the commonest hiking injuries.
One spot on a bone that you can press, most often on top of the foot, worse with every step after far more walking than usual and later aching at rest, can be a stress fracture. The commonest cause is a sudden increase in activity, and most foot stress fractures are in the long bones at the front of the foot. In a review of 70 military studies, fractures clustered in the first, hardest weeks of training and in recruits who hadn't exercised regularly before, but there was no clear evidence that heavier loads themselves raise the risk. Ankle and foot stress fractures were about twice as common in women (5.78 against 2.76 per 1,000 person-years). These figures come from soldiers, not hikers.
Numb, white, then painful toes after days of cold, wet feet can be non-freezing cold injury (trench foot), which a review says can happen when wet socks and boots aren't changed on hikes, and which can leave lasting nerve pain; hard, frozen skin after freezing temperatures is frostbite. A calf, thigh or buttock ache as you walk that goes after a few minutes' rest can be narrowed arteries.
Sources 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 4, 26, 27, 28, 29, 30, 31, 32, 33
When a scan or test helps, and how it usually goesStrong evidence
Rarely at first. After a twisted ankle or foot, clinicians use the Ottawa rules to decide on an X-ray: across 27 studies of 15,581 people they missed almost no fractures and cut unneeded X-rays by 30% to 40%. A suspected stress fracture needs checking even with a normal X-ray, because a tiny crack is often hard to see at first; a magnetic resonance imaging (MRI) scan or a bone scan finds it earlier. Plantar heel pain and Morton's neuroma are diagnosed from the story and examination. Any new foot problem with diabetes needs the foot team, not a scan first.
Most blisters heal in about a week (NHS inform says 3 to 7 days), most sprains feel better after about 2 weeks, with recovery by about 8 to 12 weeks, and pain on top of the foot usually gets better in a few weeks. Foot stress fractures usually take 6 to 8 weeks to heal. Plantar heel pain can be slow: in 174 hospital-referred patients, 80.5% still had symptoms a year after they started, and about half at 5 years; most people seen in primary care do better, and NHS inform asks you to see a professional if it hasn't improved within 12 weeks. No one can promise a date.
Sources 34, 26, 16, 10, 35, 36, 25, 37, 17
