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What's a Bone Stress Injury (BSI)?

Updated: Aug 11, 2023

Written by: Sean Rimmer, PT, DPT, OCS

of Run Potential: Rehab & Performance in Colorado Springs, CO

Bone stress injury sites in running and athletics
Bone Stress Injury Sites

Common Areas of BSI injuries in sport (shown above).

Bone stress injuries (BSI) are bony injuries due to repetitive stress without adequate recovery. Bone stress injuries occur within a continuum (grade 1-4 based on MRI findings) of mild stress reaction (grade 1) to stress fracture (grade 4). A grade 1 BSI demonstrates mild periosteal edema (swelling/fluid along a portion of the bone), and a grade 4 BSI demonstrates periosteal and bone marrow edema (swelling/fluid on the inner and outer portion of the bone) as well as a fracture line within the bone.

Unfortunately, BSI are common in runners within the lower extremity due to the repetitive sub-maximal loading in running. Common BSI sites in runners are as follows (starting from the feet to the pelvis): Metatarsals in the feet, calcaneus (heel bone), tibia and fibula (lower leg bones), femoral shaft (thigh bone), femoral neck (thigh bone near hip), and the sacrum (tailbone).

BSI can further be identified as high risk, medium risk, and low risk sites which is described in the literature based on healing potential within the bone sites. The high-risk BSI sites which include the femoral neck, anterior tibia, the navicular, and the base of the 5th metatarsal are in a more challenging position to heal due to the poor blood supply and bony tensile loads in that region. Medium risk BSI sites include the sacrum and calcaneus. The low-risk BSI sites which include the posterior tibia, fibula, and metatarsal shafts 2-4, have an improved blood supply and are stressed more so due to compressive loads.

With all that being said, it's important to understand if you have a BSI in a low or high-risk site as this will drastically alter the rehab and recovery process! Here are some points to consider which may indicate a BSI:

  • Bony tenderness to pressure or the touch (much easier to identify in the feet and lower leg due more superficial bone)

  • Vague pain that comes on in the lower body, which is worse with longer duration running, faster running speed, or downhills.

  • Pain worse with weight-bearing which starts with running but progresses to just walking or being on your feet.

  • Pain that does NOT warm-up within a run.

  • Typically, symptoms begin at ~4 weeks after starting a new and building training cycle.

***If you have any suspicion for a BSI, it's best to get checked out early! When they are caught early at a lower grade, the recovery process is shorter, and outcomes are typically much better.


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