Working Diagnosis:
Nondisplaced longitudinal stress fracture of the proximal right tibial metaphysis with associated popliteus tendinopathy and concurrent bilateral patellofemoral pain syndrome.

Treatment:
The patient was initially made non-weight-bearing for 2 weeks.

Concern was raised for Relative Energy Deficiency in Sport after she reported irregular menstrual cycles during the preceding 4 months. Despite an overall reassuring medical evaluation, Sports Nutrition assessment identified inadequate caloric intake relative to her activity level, and a nutritional intervention plan was implemented.

After 4 weeks of protected activity, she was able to ambulate and perform activities of daily living without pain.

Gait analysis demonstrated heel striking with knee hyperextension during running, likely exacerbated by underlying hypermobility. She subsequently worked with a physical therapist experienced in treating hypermobile athletes, focusing on isometric strengthening, gait retraining, and gradual return-to-running progression.

Outcome:
The patient successfully progressed through rehabilitation and gradually resumed recreational running.

Following correction of biomechanical deficits and implementation of a structured return-to-running program, she returned to her desired activity level without recurrence of symptoms.

Author's Comments:
Longitudinal tibial stress fractures are uncommon and may be overlooked because symptoms often resemble more common causes of knee pain in runners. Unlike the more familiar transverse tibial stress fractures associated with repetitive axial loading, longitudinal stress fractures are thought to result from repetitive torsional and rotational forces acting across the tibia and may be difficult to identify on initial radiographs.4-7

This case also highlights the importance of considering underlying biomechanical contributors in athletes with hypermobile Ehlers-Danlos syndrome. Joint hypermobility, altered gait mechanics, and muscular compensation patterns may increase susceptibility to unusual overuse injuries that do not fit traditional training-volume risk profiles. Additionally, the coexistence of popliteus tendinopathy raises the possibility that abnormal rotational forces across the knee contributed to both pathologies.1-3

This case further emphasizes the value of evaluating for Relative Energy Deficiency in Sport and other modifiable risk factors whenever a stress injury is identified in a young athlete.

Editor's Comments:
This case demonstrates the importance of maintaining a broad differential diagnosis for persistent medial knee pain in runners, particularly when symptoms appear disproportionate to examination findings. Although patellofemoral pain syndrome and other overuse conditions are common, focal bony tenderness should prompt consideration of an underlying stress injury even when radiographs are normal.4-7

A notable teaching point is the association between hypermobility and altered running mechanics. In this patient, knee hyperextension, heel striking, and underlying hypermobile Ehlers-Danlos syndrome may have contributed to abnormal loading patterns resulting in an unusual longitudinal tibial stress fracture. The concurrent presence of popliteus tendinopathy is also notable given the role of the popliteus in controlling tibial rotation and posterolateral knee stability.1-3

This case additionally highlights the importance of assessing nutritional status and potential Relative Energy Deficiency in Sport in athletes presenting with stress injuries, regardless of training volume. Successful recovery required not only fracture management but also correction of biomechanical and nutritional risk factors that may contribute to injury recurrence.

References:
1. Nyland, J., & Jakob, R. P. (2024). Popliteus muscle. In StatPearls. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK526084/

2. S M Blake, N J Treble; Case Report: Popliteus tendon tenosynovitis; Br J Sports Med; 2005

3. John Nyland et al.; Anatomy, Function, and Rehabilitation of the Popliteus Musculotendinous Complex; Journal of Orthopaedic & Sports Physical Therapy; March 2005

4. Keating, J. F., Beggs, I., & Thorpe, G. W. (1995). 3 cases of longitudinal stress fracture of the tibia. Acta Orthopaedica, 66(1), 41-42. https://doi.org/10.3109/17453679508994637

5. Krauss, M. D., & Van Meter, C. D. (1994). A longitudinal tibial stress fracture. Orthopaedic review, 23(2), 163-166.

6. Shearman, C. M., Brandser, E. A., Parman, L. M., el-Khoury, G. Y., Saltzman, C. L., Pyevich, M. T., & Boles, C. A. (1998). Longitudinal tibial stress fractures: a report of eight cases and review of the literature. Journal of computer assisted tomography, 22(2), 265-269. https://doi.org/10.1097/00004728-199803000-00020

7. Umans, H. R., & Kaye, J. J. (1996). Longitudinal stress fractures of the tibia: diagnosis by magnetic resonance imaging. Skeletal radiology, 25(4), 319-324. https://doi.org/10.1007/s002560050088

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