Stress response or stress reaction is the early result of bone failing to withstand a repetitive, cumulative loading force.
Stress response of bone is synonymously used with 'stress reaction' and is an early form of osseous 'stress injury', which also encompasses a stress fracture 1,2.
A stress response is the early form of osseous stress injury, leading to morphologic alterations in the bony structure and will eventually lead to a stress or insufficiency fracture, if the causative repetitive loading force continues and is not omitted 2.
A stress response can occur either as typical overuse injury on normal bone (fatigue) or in a normal activity affecting weakened bone (insufficiency). In an overuse situation, the weight-bearing parts of bone are affected, whereas in insufficiency related stress reactions the trabecular bone tends to be involved 1,2.
Stress injuries are more common in the foot and the lower leg though can occur anywhere.
High-risk locations are the femoral neck, anterior cortex of the tibia, medial malleolus, navicular bone, talus, proximal 2nd and 5th metatarsal, patella, great toe sesamoid 3.
Imaging findings may be found in compact bone or trabecular bone.
May show a subtle cortical thickening or periosteal alterations or signs of callus formation in later stages, early usually does not show anything.
There might be may mild density changes in the trabecular bone due to effacement of the fatty marrow, often better appreciated on dual-energy CT.
A stress response is characterized by a bone marrow edema like appearance with no obvious fracture cleft or cortical defect and with possible endosteal and/or periosteal edema. A stress reaction might be difficult to differentiate from a stress fracture and in that case, should be called stress injury 1.
- T1: mildly hypointense, with effacement but not a replacement of the fatty marrow
- T2FS/PDFS: hyperintense
- focal radiotracer uptake on bone scintigraphy
Treatment and prognosis
Treatment typically includes activity modification, restricted impact activities e.g. weight-bearing,
Non-steroidal anti-inflammatory drugs should be avoided as these may impair bone healing 3.
- stress fracture: no fracture line or cleft
- osteomyelitis: marrow replacement and not marrow effacement
- osteitis: difficult to differentiate
- osteoid osteoma
- 1. Palmer W, Bancroft L, Bonar F, Choi JA, Cotten A, Griffith JF, Robinson P, Pfirrmann CWA. Glossary of terms for musculoskeletal radiology. (2020) Skeletal radiology. doi:10.1007/s00256-020-03465-1 - Pubmed
- 2. Pathria MN, Chung CB, Resnick DL. Acute and Stress-related Injuries of Bone and Cartilage: Pertinent Anatomy, Basic Biomechanics, and Imaging Perspective. (2016) Radiology. 280 (1): 21-38. doi:10.1148/radiol.16142305 - Pubmed
- 3. Nye NS, Covey CJ, Sheldon L, Webber B, Pawlak M, Boden B, Beutler A. Improving Diagnostic Accuracy and Efficiency of Suspected Bone Stress Injuries. (2016) Sports health. 8 (3): 278-283. doi:10.1177/1941738116635558 - Pubmed
- 4. Goolsby MA, Boniquit N. Bone Health in Athletes. (2017) Sports health. 9 (2): 108-117. doi:10.1177/1941738116677732 - Pubmed