What is Stress Fractures?
Stress fractures, also known as “march foot”, were first recorded in the mid-19th century among military personnel. These individuals experienced foot pain and swelling, often as a result of intense training. Stress fractures happen in standard bones that face unusual pressure, similar to what military training can impose.
German surgeon, Julius Wolff (1836-1902), proposed that bones adjust and reconstruct themselves based on the stress they bear. But, a stress fracture happens when the normal remodeling process of the bone can’t keep up with the pressure. This process of remodeling is usually done by two types of cells: osteoclasts, which break down old bone, and osteoblasts, which form new bone.
For example, during intense physical activities like military training, the body can’t adjust swiftly enough leading to small cracks in the bone or microfractures. If the intense activity continues, these small cracks eventually become a bigger fracture. Typically, symptoms of a stress fracture start to appear about three weeks after a sudden increase in physical activity. It usually begins with pain after the activity, which progressively lasts longer over time.
What Causes Stress Fractures?
Stress fractures are often the result of a sudden increase in physical activity or changes in your exercise routine. Lots of things can contribute to getting these kinds of injuries, but most of the information we have comes from studies done on people in the military. Some risk factors are things you can’t control, like poor physical condition, being female, having a hormonal or menstrual disorder, having low bone density, reduced muscle mass, knees that bend inward, or a shorter leg. Other risk factors are tied to lifestyle and habits, like participating in high-impact sports like running or jumping, a sudden increase in physical activity, running on uneven or angled surfaces, wearing ill-fitting or worn-out shoes, not getting enough vitamin D and calcium, and smoking. The most common risk factor, though, is a sudden increase in activity. In fact, one study found that men who had done intense physical activity before entering military training were less likely to get a stress fracture.
It’s also worth noting that, even when men and women athletes follow the same exercise routine, female athletes are more likely to get stress fractures. But this doesn’t necessarily apply to everyone who runs. Unlike runners, people in the military often include smokers and people who are less fit. They don’t run as much in training, they have to carry heavier loads, and their shoes may not be as good at protecting against injuries. The people most at risk for stress fractures are female athletes and people who’ve had a stress fracture before.
The most common places to get a stress fracture, in descending order, are the metatarsals (the long bones in the foot), tibia (shin bone), tarsals (small bones in the foot), femur (thigh bone), and fibula (a bone in the lower leg). The pelvis is also a common site. For female athletes, stress fractures often happen in the pelvis and metatarsals. Stress fractures in the upper body are rare, but they do happen, especially in gymnasts, weightlifters, and athletes in throwing sports. They’re most likely to occur in the clavicle (collarbone), scapula (shoulder blade), first rib, upper humerus (upper arm bone), inner elbow, elbow tip, and wrist.
Certain sports are associated with stress fractures in specific areas. Runners often get stress fractures in the shin and foot bones, and female runners may get pelvic stress fractures. Long-distance runners are more likely to injure the top of the thigh bone and the pelvis. Hurdlers are more likely to fracture the kneecap. Gymnasts, female soccer players, certain positions in American football like offensive linemen and linebackers, and Olympic-style weightlifters have a higher risk for a special kind of stress fracture caused by bending the spine backward too much.
Risk Factors and Frequency for Stress Fractures
Stress fractures are a common sports injury, making up about 20% of all injuries in sports medicine. These injuries are particularly prevalent among runners, especially those running more than 25 miles a week, and military members due to their intense, repetitive training. These groups are at a higher risk, with stress fractures making up almost 16% of all injuries for runners. This type of injury often affects different parts of the body, including the tibia, tarsal navicular, metatarsals, femur, and pelvis. Additionally, women are more likely to experience these injuries.
There are several factors that can influence the likelihood of developing a stress fracture. This includes a theory known as the neuromuscular hypothesis. According to this theory, if muscles become fatigued or lose mass, they become less effective at absorbing forces that are applied to the bones, which can lead to increased stress and eventual injury. One study, for example, found that military trainees who lost the most weight (primarily muscle, not fat) in the shortest amount of time, were more likely to develop a stress fracture.
Overtraining and under-eating, also known as relative energy deficiency syndrome, is another factor that can lead to stress fractures. This is often seen in female athletes who train too much and eat too little, leading to hormonal imbalances and weakened bones. Male athletes with similar training and eating patterns can experience the same issue.
Lastly, vitamin D levels can also influence the likelihood of a stress fracture. Research has shown that individuals with lower levels of vitamin D are more likely to experience a stress fracture. Further, one study found that vitamin D supplements could potentially prevent a significant proportion of trainees from developing a stress fracture.
- Stress fractures make up about 20% of sports injuries.
- Runners and military members are particularly at risk.
- These injuries typically affect the tibia, tarsal navicular, metatarsals, femur, and pelvis.
- Stress fractures are more common in women.
- Factors influencing stress fractures include muscle fatigue or loss, intense training coupled with insufficient calorie intake, and low vitamin D levels.
Signs and Symptoms of Stress Fractures
People often notice pain linked with stress fractures after they’ve been physically active. This pain gradually worsens and lasts longer after each exercise session. If an individual continues their training routine, they may wake up with this pain the morning after activity. Other helpful information when diagnosing these injuries includes changes in training or diet, any relevant risk factors, medical history, and current medications.
An examination can offer some clues about a stress fracture. For example, the patient may have tenderness and some swelling at the fracture site. The use of a tuning fork or low-pulsed ultrasound may reproduce the pain, although these test results can vary. A couple of tests include the “hop test,” where the patient tries jumping on the affected leg, and the fulcrum test, putting tension on a long bone suspected of being fractured. However, these tests haven’t been thoroughly studied. Usually, patients with stress fractures have specific tender spots, especially along their shinbone or over the midfoot area.
Certain types of stress fractures, like spondylolysis and spondylolisthesis, require more careful detection. Spondylolysis may not cause symptoms and could be unexpectedly spotted on back x-rays. If an athlete has lower back pain and spondylolysis is suspected, stretching the lower back may worsen the pain. Testing for this involves bending one knee and extending the lower back (the Stork test). However, this test isn’t consistently reliable. If the pars defect found in spondylolysis does not heal, the vertebrae can shift and cause a condition called spondylolisthesis.
In general, the diagnosis of a stress fracture often involves a history of fast-paced physical activity, progressively worsening pain during exercise, and a high suspicion for this type of injury.
Testing for Stress Fractures
When checking for stress fractures, the first step is usually to do a plain radiograph, or X-ray. This is because it is easily accessible, not too costly, and doesn’t expose the patient to a lot of radiation. The X-ray will look for changes in both the outer and inner bone surface. If the athlete continues to train despite the fracture, a fracture line will appear. In some types of bone, the X-ray might show hardening, known as ‘sclerosis’. It’s important to note that it usually takes about 2-3 weeks for these changes to become clearly visible on an X-ray.
In the case of spondylolysis, a condition of the spine, plain X-rays can be tricky. To get a good view, five different images are needed. However, these can sometimes miss early changes in the bone. If the X-rays don’t show anything but the doctor still suspects something is wrong, there are three more tests that they might use – single-photon emission computerized tomography, computed axial tomography, and magnetic resonance imaging.
3 phase bone scans are another option. These involve using a tracer that is absorbed in areas with a lot of bone activity. This is very specific, so if it doesn’t show anything, a stress fracture is very unlikely. However, it is not very sensitive, so certain conditions like cancer or osteomyelitis can produce similar results. The downside is that it is not very useful for follow-up images.
Computer tomography, or CT scans, are also used for stress fractures. They are not as sensitive as magnetic resonance imaging (MRI) but are more widely available. However, they do expose patients to more radiation.
Magnetic resonance imaging (MRI) has excellent accuracy. However, the main downside is the cost of the procedure and its limited availability. MRI scans can be graded from 1 to 4 depending on the severity of the stress fracture.
Overall, blood tests do not generally aid in diagnosing stress fractures unless they happen very often. In case of recurring stress fractures, tests would include thyroid-stimulating hormone, parathyroid hormone, and a bone mineral density study.
Treatment Options for Stress Fractures
Stress fractures are categorized as high-risk and low-risk. Treatment often involves resting and avoiding weight-bearing activities for about 2 to 6 weeks, followed by slowly getting back into physical activities.
Low-risk stress fractures usually occur in areas such as the back of the shinbone, second to fourth metatarsal bones in the foot, thighbone, pelvis, sacrum (part of your lower spine), and calf bone.
High-risk stress fractures occur in areas with less blood supply and are more likely to crack under pressure, making them more difficult to heal. Doctors often need to be extra vigilant when diagnosing these fractures as they are commonly found in places that bear a lot of weight and are at high risk of not healing properly. They typically appear in the neck of the thighbone, front of the shinbone, navicular bone in the foot, talus bone in the ankle, sesamoid bones in the foot, and the first and fifth metatarsal bones. These fractures don’t always respond well to conventional treatments and often lead to long-term issues.
The neck of the femur, or thighbone, is a high-risk location where stress fractures often occur. In cases where a stress fracture is suspected here, doctors usually recommend an MRI as X-Rays may not clearly show these injuries. There are two types of fractures that can occur in the femur neck. Fractures on the upper (tension) side should be looked at by a surgeon. However, those on the lower (compression) side can often be managed without surgery, if the fracture line is less than half the width of the bone, although it requires close monitoring. But if the pain gets worse or the size of the fracture increases, then a consultation with a surgeon is warranted. If the fracture becomes displaced it should be treated urgently due to the risk of the thighbone head losing its blood supply.
Patients might also find calcium and vitamin D supplements helpful, though research hasn’t clearly shown that these speed up the healing process. One study found that female athletes taking a calcium supplement were three times more likely to experience stress fractures.
Spondylolysis, a specific kind of stress fracture in the back, can be challenging to treat due to the lack of large clinical trials. The recommended treatment is generally to rest and strengthen the core muscles, perhaps with bracing. Rest can range from as little as 2 weeks to as long as 6 months, depending on how long it takes for the pain to go away. Though some controversy surrounds its use, a brace that limits movement of the lower back, worn for up to 23 hours a day and up to 6 months, can be helpful. Physical therapy that focuses on strengthening the core and stabilizing the spine may also be beneficial, leading to a gradual return to physical activities. If these methods don’t work, surgery may be an option.
What else can Stress Fractures be?
When a patient complains of pain, doctors must consider several possible health problems that might be the cause. These include:
- Cellulitis, which is a severe skin infection
- Exertional compartment syndrome, a muscle and nerve condition caused by high-pressure buildup from strenuous exercise
- Osteomyelitis, an infection in the bone
- Tendonitis, an inflammation or irritation of a tendon
- Tendinopathy, a degenerative condition of the tendon
- Various types of tumors, both benign (non-cancerous) and malignant (cancerous)
- Nerve entrapment, which occurs when a nerve is compressed
- Arterial entrapment, a condition in which an artery is compressed
- Coagulation disorders, which hinder the blood clotting process
- Compartment syndrome, a painful condition that occurs when pressure within the muscles builds to dangerous levels
- Neuropathic pain, a type of pain resulting from nerve or tissue damage
- Complex regional pain syndrome, a chronic pain condition affecting a limb usually after an injury
All these conditions can cause similar symptoms, so doctors have to conduct tests and assessments in order to determine the actual health issue.
What to expect with Stress Fractures
Typically, stress fractures that are deemed low-risk can heal effectively, allowing the athlete to get back to their previous level of activity. However, a proper recovery period and a gradual return to activity will be required.
Possible Complications When Diagnosed with Stress Fractures
Low-risk stress fractures usually don’t have many complications. Sometimes, patients might still experience some pain afterwards. High-risk stress fractures, on the other hand, can cause more serious issues. These can worsen to a point where the bone doesn’t heal and needs surgery. Athletes suffering from these types of fractures may need to switch sports, and they might experience more pain even after recovery.
Common Complications:
- Residual pain for low-risk fractures
- Progression towards non-healing bone (non-union) for high-risk fractures
- Need for surgical treatment for high-risk fractures
- Change in the sport for athletes
- Greater post-recovery pain for high-risk fractures
Recovery from Stress Fractures
Both high-risk and low-risk stress fractures need to go through the same basic rehabilitation process. This includes a period of immobilization, which allows the fracture to heal itself. Often, high-risk injuries will need an operation to stabilize the injury. Rehabilitation follows a two-part structure.
The first phase is referred to as active rest. During this phase, the injured area is kept immobilized to prevent further harm while maintaining aerobic fitness through low-impact activities such as cycling, deep water running, swimming, and zero-gravity running. After the patient has experienced no pain for around one to two weeks, they can progress to the second phase.
In phase two, the focus is on rehabilitation that includes muscle strengthening exercises, improving the sense of balance and bodily position (proprioception), core and pelvic exercises, and working towards restoring the patient’s fitness to the level prior to the injury. The ultimate objective is to get them back to their usual activities.
In cases where the patient is a runner who has suffered a stress fracture, it could be beneficial to have a gait analysis. This can provide useful insights to guide the rehabilitation process. Once ready for running, it’s always a good plan to start slow and gradually increase time, intensity, and distance by no more than 10 percent per week. This helps to avoid re-injury.
Preventing Stress Fractures
The best way to prevent stress fractures is to tackle both internal and external risk factors. External risk factors are easier to address. This can be done by ensuring you get enough calcium and vitamin D, wearing appropriate shoes, gradually increasing exercise levels, selecting the right running surfaces, and quitting smoking. However, internal risk factors are more challenging to change, but it’s crucial to understand how they can combine with the external risk factors to increase the risk of stress fractures in athletes.
There are risk factors such as inadequate physical fitness, hormonal imbalances, menstrual disorders, reduced bone density, and reduced lower body muscle mass, which can be addressed and improved. However, certain factors such as being a female, having knees that knock together (genu valgum), and potential differences in leg length can’t be changed. Nonetheless, they should be taken into account when planning training routines to help reduce the risk of stress fractures.
