Bone stress injuries in runners: spotting the high-risk ones early

The shin pain that doesn't warm up

A runner is a few weeks into a marathon block. The shin started as an ache after longer runs. Now it's sore earlier in each run, it doesn't ease off once they're warm, and the stairs at work have started to bother them.

It's easy to file that under "shin splints" and start on load management and calf work, and often that's a reasonable call. Some of these presentations are bone stress injuries, though, and a small number sit at sites where missing them early changes the outcome: a longer lay-off, a complete fracture, or an operation that might have been avoided.

This article goes through what a bone stress injury is, what the history and examination should pick up, why the site matters more than almost anything else, when a normal X-ray shouldn't reassure you, and what to ask about energy availability.

What a bone stress injury is

The 2022 Nature Reviews Disease Primers review by Hoenig and colleagues describes bone stress injuries as overuse injuries that occur when excessive repetitive loads are introduced to a generally normal skeleton. The prevailing theory is an imbalance in bone metabolism, where microdamage builds up faster than targeted remodelling can remove and replace it.

Warden, Davis and Fredericson (JOSPT, 2014) describe it as a continuum. It begins as a stress reaction, can progress to a stress fracture and, ultimately, to a complete fracture. They also point out that bone stress injuries in runners tend to recur, which is why the underlying causes matter as much as the injury itself.

They're not rare in active people. A 2015 review of lower-limb stress fractures in runners (Kahanov and colleagues) puts stress fractures at between 1% and 20% of athletic injuries, with 80% of them in the lower extremity. Hoenig's review gives a one-year incidence in athletes of 5% or less, and reports that bone stress injuries occur 1.8 to 2.3 times more often in female than in male athletes, which the authors partly link to low energy availability being more common in active women.

The history: what to ask

Hoenig's review says suspicion should rise with a few key risk factors: an "at-risk" activity such as running, a previous bone stress injury, current activity levels, and any indicators of relative energy deficiency in sport (REDs) or the female or male athlete triad.

A few questions do most of the work.

What changed in the last four to six weeks? The review notes there's usually a delay between a change in activity and the onset of symptoms, so look back over that window. The change might be one big jump in duration, frequency, intensity or type of training, or several small changes at once. A training log helps. So does asking about load outside training, such as a new physical job or a weekend of hiking.

Has this happened before? A previous bone stress injury is one of the risk factors the review lists, and the tendency to recur is well described.

How does the pain behave? The review describes a range from a mild, diffuse ache after a certain amount of activity to localised, sharp pain every time the bone is loaded. Most bone stress injuries are pain-free when unloaded, but advanced ones can hurt at rest, including at night.

Is there anything suggesting low energy availability? Low energy availability can come from eating too little, training too much, or both. In women it often shows up as menstrual dysfunction such as amenorrhoea. In men it may present as reduced libido or sexual function. Hoenig's review calls low energy availability a major risk factor for bone stress injuries in both sexes.

That last question can feel awkward in an MSK appointment. It's still part of the history, and a missed period or a recent drive to lose weight before a race is clinically relevant information.

The examination: tenderness, hopping, and what not to rely on

According to the review, the cardinal sign is localised bone tenderness that's aggravated by loading and doesn't "warm up" as activity continues. At subcutaneous sites like the tibial and metatarsal shafts and the tarsal bones, that tenderness is easy to find, and there may be local swelling, redness or warmth.

The extent of the tenderness helps. In a prospective study of 429 elite infantry recruits in the Israel Defense Forces (Milgrom and colleagues, J Sci Med Sport, 2021), medial tibial stress fractures occurred when the band of tibial tenderness was 10 cm long or less. A positive hop test alongside tibial pain and tenderness was associated with a significantly higher rate of stress fracture, while tibial pain scores didn't predict it. Hoenig's review cites the same 2021 study for a hop test sensitivity of 100% and specificity of 45% for tibial stress fractures, so a negative hop test may help rule one out. A positive one, on its own, doesn't rule one in. These were military recruits, so treat the numbers as a guide rather than a precise prediction for a recreational runner.

Deeper bones covered by muscle, like the femoral neck and shaft, give less localised and more confusing symptoms. The review mentions specific loading tests: hopping on the affected limb, the fulcrum test for the femoral shaft, and the squeeze test for the calcaneus.

Two older bedside tests don't hold up well. A 2012 JOSPT systematic review and meta-analysis (Schneiders and colleagues) found therapeutic ultrasound had a pooled sensitivity of 64% and specificity of 63% for lower-limb stress fractures, and tuning fork results were too inconsistent to pool, with sensitivity ranging from 35% to 92% and specificity from 19% to 83%. The authors didn't support either as a standalone diagnostic test.

Keep the differential open. The review lists tendinopathy, muscle strain, ligament sprain, arthritic processes, osteomyelitis and neoplasms. Night pain can come from an advanced bone stress injury, but it's also the symptom that should make you check for anything that doesn't fit.

The site decides the risk

This is the part that changes what you do next. Bone stress injuries are classified as low or high risk according to where they are.

Hoenig's review describes high-risk sites as those with a higher risk of delayed union, non-union, complete fracture, re-fracture or failure to return to sport on time. Many share high tensile rather than compressive forces and a poor blood supply, and they occur in weight-bearing bones. Typical high-risk sites include:

• the femoral neck
• the patella
• the anterior tibia
• the medial malleolus
• the talus and tarsal navicular
• the base of the fifth metatarsal
• the great toe sesamoids

Low-risk sites in the review's classification include the posteromedial tibia, the fibula, the femoral shaft, the shafts of the first to fourth metatarsals and the calcaneus.

A 2023 British Journal of Sports Medicine systematic review and meta-analysis (Hoenig and colleagues) tested whether location really does predict outcome. Across 76 studies and 2,974 bone stress injuries, return to sport took longest for the tarsal navicular (127 days on average) and the femoral neck (107 days), and was quickest for the posteromedial tibial shaft (44 days) and the fibula (56 days). More than 90% of athletes returned to sport overall. Complication rates were highest for the femoral neck, tarsal navicular, anterior tibial shaft and fifth metatarsal.

So a runner with focal tenderness on the posteromedial tibia and a runner with focal tenderness on the front of the tibia might describe similar pain. They aren't the same clinical problem. On plain X-ray, the review notes, a visible defect can indicate a very high-risk injury such as an anterior tibial stress fracture, where the appearance is known as the "dreaded black line".

The one not to miss: the femoral neck

Femoral neck stress fractures are uncommon. Robertson and Wood's 2017 current concepts review (Sports Medicine International Open) puts them at about 3% of sport-related stress fractures, with marathon and long-distance running the most common causative sports. They matter because delay is common and the consequences of displacement are serious.

The typical story is a gradual onset of poorly localised hip or groin pain, aggravated by activity and weight-bearing and settling with rest. In one study cited in the review, 87% of patients had pain in the anterior groin, but it can also sit in the thigh or buttock and refer to the knee. There's often a recent increase in training, such as building up for a marathon. The pain usually appears late in a run at first, then earlier, and eventually at rest and at night.

Examination findings are often non-specific. The most consistent is pain at the extremes of hip movement, especially internal rotation (79% in one study). Tenderness over the front of the hip and groin was found in 62%, and pain may be provoked by a straight-leg raise or by log-rolling the thigh. Heel-strike testing was positive in only 6%, so a negative heel strike tells you very little.

The review is clear about what happens next. As soon as a femoral neck stress fracture is suspected, the person should stop weight-bearing on that hip and have an urgent screening X-ray. A normal film doesn't settle it. As many as two thirds of patients show no change on X-ray at presentation, changes typically take six to eight weeks to appear, and around half never show changes on X-ray at all. MRI is the recommended next investigation whenever the X-ray is negative and the history and examination still fit.

Management depends on the fracture. Incomplete compression-side fractures are managed conservatively. Complete compression-side fractures and tension-side fractures are managed surgically, and displaced fractures need urgent reduction and fixation. Return to sport rates for displaced fractures are reported as low as 33%.

For a manual therapist, the job is recognition and speed. A runner with exercise-related groin pain, pain on hip internal rotation and a recent training increase needs to stop running and be seen promptly through your local urgent medical or orthopaedic route, with clear advice to keep weight off the leg in the meantime. It isn't one to reassess next week.

Imaging: why a normal X-ray doesn't close the question

The wider imaging evidence matches the femoral neck picture. A 2016 American Journal of Sports Medicine systematic review of imaging for suspected lower-limb stress fractures (Wright and colleagues) found plain radiograph sensitivity ranged from 12% to 56%, with specificity of 88% to 96%. MRI was the most sensitive and specific test. The authors noted that X-rays are likely to give false negatives early on, and in some cases may never show the fracture.

Hoenig's review agrees. Plain radiographs lack the sensitivity to detect bone stress injuries and don't show bone oedema, while fat-suppressed MRI has become the imaging modality of choice. Fredericson's 1995 MRI work in runners showed the same continuum on imaging, from periosteal oedema, through increasing marrow involvement, to a frank cortical fracture, with the more severe grades matching clinical features like pain during daily walking and localised tibial tenderness.

That doesn't mean every sore shin needs a scan. Hoenig's review says bone stress injuries can be diagnosed clinically without imaging, and the Israeli military study found an initial treatment protocol without imaging was effective in more than two thirds of cases. The review recommends advanced imaging when a high-risk injury is suspected, when someone isn't responding to initial treatment, and in time-sensitive situations such as imminent high-level competition.

In practice, a classic low-risk tibial presentation can reasonably be managed on clinical grounds, with a clear plan to review. A suspected high-risk site, or a "low-risk" injury that isn't behaving, needs imaging and a medical opinion.

What management looks like

Hoenig's review describes most low-risk injuries healing with activity modification, followed by progressive loading and a planned return to activity. A gradual return to sport can usually start once the person is pain-free in daily activities, and the aim through each phase is to stay pain-free. Crutches depend on the site and on whether weight-bearing hurts. Low-risk injuries to the compressive sides of long bones typically don't need weight-bearing restriction unless walking is painful.

High-risk injuries are different. The review notes that non-weight-bearing immobilisation has traditionally been used for about six weeks in many high-risk cases, that a tall boot is recommended for fifth metatarsal and navicular injuries, and that people with a high-risk injury may benefit from referral to a specialist with expertise in managing them.

The return to running is only half the plan. Because these injuries recur, the causes need addressing. Warden and colleagues highlight training design, reducing impact forces (for example running "softer" or with a higher stride rate), and strengthening local muscle, such as the calf for tibial injuries and the foot intrinsics for metatarsal ones. Hoenig's review adds that gait retraining may be considered for runners with repeated bone stress injuries, and that everyone with a bone stress injury should have lifestyle factors addressed to support bone health, including appropriate nutrition, quality sleep and ways to reduce psychological stress. Low calcium and vitamin D levels have both been linked to lower bone strength and a higher risk of these injuries.

Energy availability is where you'll often need help. The 2023 International Olympic Committee consensus statement on REDs (Mountjoy and colleagues, British Journal of Sports Medicine) introduced the REDs Clinical Assessment Tool, version 2, to support detection and diagnosis through severity and risk stratification. If the history suggests low energy availability, or a woman describes missed or absent periods, the clinically useful step from an MSK clinic is to raise it sensitively and make sure the person's GP or a sports medicine doctor is involved.

What changes on Monday morning

1. Ask about the last four to six weeks. Check training volume, intensity, surface, footwear, race plans and load outside running, and look for one big change or several small ones.
2. Ask about previous bone stress injuries and energy availability. Include menstrual history in women and reduced libido in men, phrased sensitively, alongside recent weight loss or dieting.
3. Palpate the bone, not just the soft tissue. Note whether tenderness is focal or diffuse, and roughly how long the tender band is.
4. Use hop and loading tests sensibly. A negative hop test may help rule out a tibial stress fracture. Don't rely on a tuning fork or therapeutic ultrasound.
5. Name the site and its risk. Femoral neck, anterior tibia, navicular, fifth metatarsal base, medial malleolus, talus, patella and sesamoids change the plan.
6. Treat exercise-related groin pain with respect. Pain on hip internal rotation after a training increase means stopping running, keeping weight off the leg and arranging prompt medical assessment.
7. Don't let a normal X-ray end the conversation. Early films often miss these injuries. Persisting suspicion at a high-risk site needs MRI and a medical opinion.
8. Plan the cause, not just the comeback. Training design, impact, local strength and bone health all need a place in the plan.

Most bone stress injuries heal well with modified loading and a planned return to running. The skill is spotting the few that sit at a high-risk site, and moving quickly when they do.

Force application, impact absorption and how load is transmitted through the musculoskeletal system are covered in ManualCPD's Load & Leverage: The Biomechanics of Athletic Edge course, written for chiropractors and physiotherapists. ManualCPD offers online, on-demand CPD for chiropractors, physiotherapists, osteopaths and sports therapists, broken into manageable chunks you can work through between patients, at lunch or after clinic. Every ManualCPD course is accredited by The CPD Group (Provider #788442), and you receive a CPD certificate on completion.