Bone stress injuries (BSI) are overuse injuries that are characterized by a gradual onset of pain with activity. When running or jumping, for example, bone experiences micro-trauma. This micro-trauma is normally beneficial and allows the bone to heal stronger and more robustly.
When bone is repetitively loaded in excess (i.e. a significant and sudden increase in running volume), without proper recovery, the bone healing is unable to overcome the micro-trauma that is occurring.1
Osteoclasts: Cells that break down old or damaged bone to allow for new bone growth/repair.
Osteoblasts: Cells that form or heal bone (osteogenesis).
Bone Stress Continuum
BSIs in runners occur on a continuum, beginning with a stress reaction, progressing to a bone stress fracture. If untreated, a complete fracture develops.1
- Stress Reaction
Micro-damage to bone presents as a focal ache when running, jumping, and eases at rest. In progressive cases – walking/standing. Medical imaging identifies a stress response as varying levels of edema or “swelling” in the bone.
- Stress Fracture
Presenting as either a single or many small fracture lines throughout the affected bone area. Pain can be very pronounced with direct pain to the touch, aggravated by activity, and possibly painful at rest. Pain in the evening and at night are further indicators of an inflammatory component. Weight bearing activities, sports in particular, will likely become less and less tolerable at this point due to pain. Medical imaging identifies stress fractures as a definitive fracture line.
- Complete Fracture
An untreated stress fracture becomes a complete fracture when the fracture line extends across and through the bone entirely. Symptoms are far progressed, and all weight bearing is painful, running/jumping are often intolerable at this stage.
Bone Stress Injury Occurrence and Demographics
Studies suggest that stress fractures account for 15-20 percent of all musculoskeletal related injuries. Stress fractures were most common in athletes between the ages of 15-19 years old at 42.6 percent, followed by patients over 60 years old at 37.3 percent.2
Stress fractures are most common among distance runners. The most prevalent regions include the navicular, tibia, metatarsals, femoral head, and fibula.
Severity of stress fractures are largely characterized by the specific bone’s ability to heal without surgical intervention. The primary factors in determining a bone’s ability to heal is the amount of blood supply that particular bone receives and the amount of load that bone endures with weightbearing. Low risk suggests that this region is more likely to heal without surgical intervention. On the contrary, high risk suggests that surgical intervention is often required.3
Common Anatomical Locations and Risk of BSI
Low Risk
- Posteromedial tibia
- Fibula/lateral malleolus
- Calcaneus
- Diaphysis of 2nd-4th mets
Medium Risk
- Pelvis (sacrum & pubic rami)
- Femoral shaft
- Proximal tibia
- Cuboid
- Cuneiform
- Calcaneus
High Risk
- Femoral neck
- Patella
- Anterior tibial diaphysis
- Medial Malleolus
- Talus (lateral process)
Factors Contributing to BSIs
The development of BSIs is often due to numerous factors cumulative and compounding overtime – overloading bone. Factors can be broken down to two categories: Factors impacting how load is applied to bone OR factors impacting the ability of bone to resist load.1
Factors Impacting How Load is Applied to Bone*
- Biomechanics – “Running form”
- Training Factors – Duration, frequency, and intensity of training sessions
- Muscle Strength and Muscle Endurance
- Training Surfaces and Terrain – Asphalt/Concrete/Trail (uneven vs level)
- Shoes and Orthotics
Factors Impacting the Ability of Bone to Resist Load**
- Genetics
- Diet/Nutrition – Caloric intake, Vitamin D and Calcium intake, eating behaviors
- Hormone function – Menstrual status in women, testosterone levels in men
- Physical activity level
- Bone Diseases
- Medications
*Before making significant changes to your running mechanics, fitness routine and shoes – consider seeking advice from a physical therapist that specializes in treating runners.
**Before making changes to your diet/medications, consider consulting your doctor and a sports nutritionist.
Insufficiency vs Fatigue Stress Fractures
Given the contributing factors listed above, the cause of stress fractures can be split between two “buckets” – although both often play a role in the injury. These two “buckets” are coined insufficiency fractures and fatigue stress fractures.
Insufficiency Stress Fractures
Insufficiency Stress Fractures occur when normal load (i.e. running) is placed on abnormal or compromised bone. This type of stress fracture is often seen in younger athletes due to Relative Energy Deficiency Syndrome (RED-S) or in older adults due to osteoporosis.4
RED-S: Previously referred to as “Female Triad Syndrome”, RED-S is a more inclusive diagnosis, accommodating the increasing occurrence in male athletes and the additional components associated with the condition.
RED-S occurs when an athlete under fuels – when they do not consume enough nutrient dense calories to meet the needs of their physical activity, training, and daily life. Bone, hormonal function, and many other bodily components become compromised – including athletic performance.
A car without fuel can’t run… you can’t either, not for long at least.
Fatigue Stress Fractures
Fatigue Stress Fractures occur when abnormal load is applied to normal bone. In other words, a sudden increase in frequency, duration, and intensity can cause accumulated micro damage beyond the normal pace of bone healing.
Bone stress injuries are common among athletes and active individuals, often starting with minor discomfort and progressing if untreated. Understanding the causes and signs can help you take action before a small issue becomes a bigger problem. Stay mindful of your body, and if you’re experiencing symptoms, seek professional advice to keep moving safely.
Resources
- Warden, Stuart. “Management and Prevention of Bone Stress Injuries in Long …” Journal of Orthopaedic & Sports Physical Therapy, JOSPT, 2014, www.jospt.org/doi/full/10.2519/jospt.2014.5334.
- Wright, Alexis A et al. “Risk factors associated with lower extremity stress fractures in runners: a systematic review with meta-analysis.” British journal of sports medicine vol. 49,23 (2015): 1517-23. doi:10.1136/bjsports-2015-094828
- Gaikwad, Puja. “Bone Stress Injuries.” Physiopedia, www.physio-pedia.com/Bone_Stress_Injuries. Accessed 4 Sept. 2024.
- Hampton, Lucinda. “Insufficiency Fracture.” Physiopedia, www.physio-pedia.com/Insufficiency_Fracture. Accessed 4 Sept. 2024.
