Bone stress injuries and the effects on bone mineral density
25th June 2024 - By Kristin Haigh
Bone Stress Injuries (BSIs) are injuries that occur when bones are subjected to repetitive stress or overuse, leading to small cracks or fractures. These injuries typically result from activities that involve repeated impact, such as running or jumping. Examples of these injuries are Shin Splints (Tibial bone stress or Medial Tibial Stress Syndrome) and metatarsal (foot bones) stress fractures.
People with BSIs generally have pain that develops gradually and worsens with weight-bearing activities, and sometimes have swelling and tenderness at the injury site.
BSIs in runners commonly are in the tibia. These injuries often require a prolonged recovery period, and there is a high rate of reinjury. Popp et al. (2021) investigated the effects of a tibial BSI on the Bone Mineral Density (BMD) of female athletes. They evaluated 30 female athletes aged 18-35 years, all diagnosed with a tibial BSI. The athletes all underwent an initial period of reduced weightbearing, such as walking with crutches or a pneumatic walking boot.
From time of BSI diagnosis to 12-weeks post diagnosis, all measures of BMD declined by between 60%-95% in both the injured and uninjured legs, indicating that reduced weightbearing associated with the initial management of a BSI affects the BMD in all weightbearing bones. Weightbearing physical activity was at its lowest during the first 8 weeks of the study then steadily increased, while BMD continued to decrease until 12 weeks before beginning to increase again. This finding indicates that reintroducing higher level weightbearing and impact loading of bones takes some time to begin to produce noticeable changes in BMD. Therefore, the critical time to ensure safe and cautious progression of weightbearing is at least the first month, as re-loading in this period involves increasing the impact load on bones that may be briefly continuing to decline in BMD.
By 24 weeks, bone measurements returned to near-baseline values, and had surpassed baseline values by 1 year post-injury. 10 of the 30 participants (1/3) experienced a subsequent BSI during the re-loading period of the study. Participants of a younger age, who’d had a later age of menarche, and who’d had previous BSIs were more likely to sustain a second BSI.
To summarise, bone density declines in both legs post-BSI and does not return to baseline for 3-6 months. It’s vital to cautiously re-load impact and weightbearing to avoid overloading bones that may continue to have reduced BMD for 4 weeks. Please see your physiotherapist if you have any running-related pain or injuries.