Femoral Neck Stress Fractures: Signs, Symptoms, Return-To-Run Prognostics and Theorized Prevention
** Every two years I have to recertify my UESCA Coaching credentials. You can either retest or write a research paper. This is the paper I wrote back in 2023 that earned my recertification***
Stress fractures are a constant fear of most or all runners. While it is easy to blame pavement for these injuries, ultra/trail runners are not out of the woods just because they run on dirt. Anyone who has existed around this sport for any amount of time can attest that ultra/trail athletes are still susceptible to stress fractures. Over the last year, I have personally known three ultra/trail athletes with femoral neck stress fractures and have heard about several more. Unfortunately, I was one of them. While I was on the mend (read: really bored), I looked into this phenomenon. I was interested in learning the mechanics of the injury and if there was anything we could do, as coaches, to prevent and rehabilitate femoral stress fractures in trail and ultra runners. The following is what I learned.
Femoral neck stress fractures account for about 3% of bone stress injuries seen in athletes 2. Stress fracture symptomology can be both straight-forward and muddy. Symptoms generally present as pinpoint pain or sharp ache in bones of the feet or tibia; the hip may present without such pinpoint pain secondary to it being a larger region with increased tissue mass around the bones. Femoral neck bone stress injuries (BSI’s) generally present with anterior groin pain, increasing pain with exercise, pain with straight leg raise, pain with log roll of femur, pain with single leg hop test1. Differential diagnoses that may need to be ruled out before progressing to imaging of affected joint/bone, are hip muscle strain or labral pathology. Stress fractures tend to progress quickly and without a clear mechanism of injury unlike most muscle strains. Orthopedic tests exist to rule in/out labral pathologies and these can be done with a PT or orthopedist. Sources urge caution with all exercise-induced hip pain secondary to the gravity of incorrect or delayed diagnosis of a femoral neck BSI2. Most suspected BSIs should be urgently referred to radiographic imaging first with a subsequent magnetic resonance image (MRI) being done after continued pain, lack of progress with PT or evidence of bone injury in the radiograph. MRI’s are between 80-100% sensitive and 100% specific to BSIs2. This means that they are great options for ruling in BSIs and ruling out other diagnoses.
Once a femoral neck BSI is diagnosed, the following return to run (RTR) program is generally followed. The athlete will remain non-weight bearing (NWB) until they tolerate ambulation without gait deviation and pain. A 2016 study done by Lindsay Ramey, et. al looked into whether the MRI grade of a femoral neck stress fracture can predict an athlete’s return to running time. This study found that “RTR time in weeks for patients with fractures graded 1 to 4 was 7.4 ± 2.7 (range, 4-11), 13.8 ± 3.8 (range, 6-21), 14.7 ± 3.5 (range, 8.5-24), and 17.5 ± 3.4 (range, 10-32), respectively”3. Here, we can see that RTR time is generally dependent on how severe their BSI is graded by MRI and will range from approximately 5-20 weeks for most athletes. This study also found that athletes with lower BMIs tended to require a longer RTR interval. Though this was not the hypothesis studied, the point is interesting to note. Further rehabilitation guidelines are put forward in many papers but summarized well by G. Robertson and A. Wood in Femoral Neck Stress Fractures in Sport: A Current Concepts Review from 2017. The general guideline requires all activities of daily living to be pain free before an athlete can progress to athletic/recreational activities. This is generally around 12 weeks for femoral neck BSIs, given their classification as “high-risk” injuries 2. An athlete is likely to tolerate the elliptical and stationary bike before running is tolerated or recommended but pain provocation should guide this progression. As progression to running is recommended and cleared by MD or PT, time and speed intervals should be kept minimal and advanced cautiously. A study by Edwards, et. al. from 2010 found that in decreasing running speeds from 4.5 mph to 3.5 mph the likelihood of subsequent stress fractures could be reduced by 7% and decreases in speeds from 3.5 mph to 2.5 mph could reduce the likelihood by 10% 4. All this to say, speeds should be slow and time spent running should be low, they should also be designed and assessed for appropriateness throughout by a medical professional.
Rather than suffer extreme hip pain, potential surgery and definite time away from sport, could we not simply try to prevent BSIs from plaguing us in the first place. The answer I've found is “maybe?”. More research has been done in gait changes to address tibial BSIs and may be able to be extrapolated to the hip at this time given lack of specifics in femoral neck BSIs. A study by Meardon, et. al. from 2021 found that “Peak tibial stress increased with gait speed, with a 2-fold increase in running relative to walking”, but no runner wants to hear that they should run more slowly to reduce their risk of BSIs, so let’s look at how we can train our bones to manage stress 5. A few jumping/hopping and squatting programs have been floated as methods of increasing our bone’s tolerance to stress and to build stronger bones in the process. Mats P Mosti, in their 2014 study focusing on young women, found that 4 sets of 3-5 repetitions of squats weighted at 85-90% of an athlete’s one repetition maximum (1RM) repeated 3x per week for 12 weeks can increase bone mineral density in the lumbar spine and hip 8. According to Warden et al, bone recovery of it’s mechanosensitivity occurs 4-8 hours after a loading session and therefore be optimized with a second bone loading activity later in the day after a run. Researchers have suggested jumping programs of between 20-60 repetitions 10. These strength/plyometric programs (not to be done until bone injury is healthy and healed), stimulate osteoclastic and osteoblastic activity at optimal intervals to progress bone remodeling efficiently and effectively.
Femoral neck BSIs (as well as BSIs in all other bones) are serious injuries that a coach should be wary of and be able to react to quickly. The cost of a slow or nonchalant reaction to an athlete’s reports of insidious anterior hip pain could be more dire than 12-weeks away from sport but could result in surgery, a lengthened timeline of conservative management, or medical retirement. A major risk factor for missing or misdiagnosing a stress fracture is actually a psychological one according to Johansen, et al in 2017. His paper states “A majority of the athletes (76% [95%CI: 66%; 86%]) and coaches (79% [95%CI: 61%; 97%]) reported “Ignoring pain” as a risk factor for running injury.” 6. With an “A” race or big training weekend on the line, a runner or coach may minimize or ignore symptoms of pain that could be more easily taken care of with a few days or weeks of rest as opposed to months or longer.
So, now that the runner has been pulled out of activity, how is a coach able to tell when an athlete is ready to progress back into running? The return-to-run protocol should always be managed by an orthopedist or physical therapist with knowledge of the bone remodeling process. The return-to-run process will be “symptom driven. At all stages, the optimal load does not produce symptoms during, after, or the day following loading.” as summarized in Warden, et al 9. This same paper goes on to state that a proper return-to-run progression “initially focuses on increasing running volume before speed”9. There is no “one-size fits all” algorithm to return an injured athlete back to running but as long as tissue healing and loading principles are taken into consideration along with ongoing symptomology of the athlete, it will be hard to progress too quickly.
Any athlete who has a history of bone stress injuries should be assessed for nutrition deficits, blood biomarker clues and bone density by their MD as a precaution. An athlete’s nutritional intake as well as their capacity to absorb nutrients efficiently and effectively pairs with sleep, stress and training load to provide and athlete’s energy availability. Relative energy availability is crucial in an individual athlete’s ability to perform. A paper by Papageorgiou, et al, notes that “physically active individuals who have low [energy availability] present with lower bone mass, altered bone metabolism (favouring bone resorption), reduced bone strength and increased risk for stress fracture injuries.”, meaning that energy availability must be addressed for each athlete managing a BSI of any kind 11.
As coaches, we are missing the mark if we are only willing to address training volume and intensity. As running coaches, our scope may be small in this matter but we can be critically important in recognizing and properly addressing symptoms as well as guiding our athletes through the process of MD and dietician consultations, imaging, cross-training, and eventual return to sport.
References:
1. Kahanov, Leamor & Eberman, Lindsey & Games, Kenneth & Wasik, Mitch. (2015). Diagnosis, treatment, and rehabilitation of stress fractures in the lower extremity in runners. Open access journal of sports medicine. 6. 87-95. 10.2147/OAJSM.S39512.
2. Robertson GA, Wood AM. Femoral Neck Stress Fractures in Sport: A Current Concepts Review. Sports Med Int Open. 2017;1(2):E58-E68. Published 2017 Mar 15. doi:10.1055/s-0043-103946.
3. Ramey, Lindsay & McInnis, Kelly & Palmer, William. (2016). Femoral Neck Stress Fracture: Can MRI Grade Help Predict Return-to-Running Time?. The American Journal of Sports Medicine. 44. 10.1177/0363546516648319.
4. Edwards, W. Brent & Taylor, David & Rudolphi, Thomas & Gillette, Jason & Derrick, Timothy. (2010). Effects of running speed on a probabilistic stress fracture model. Clinical biomechanics (Bristol, Avon). 25. 372-7. 10.1016/j.clinbiomech.2010.01.001.
5. Meardon SA, Derrick TR, Willson JD, et al. Peak and Per-Step Tibial Bone Stress During Walking and Running in Female and Male Recreational Runners. Am J Sports Med. 2021;49(8):2227-2237. doi:10.1177/03635465211014854.
6. Johansen KK, Hulme A, Damsted C, Ramskov D, Nielsen RO. Running Injury Development: The Attitudes Of Middle- And Long-Distance Runners And Their Coaches. Int J Sports Phys Ther. 2017;12(4):634-641.
7. Warden SJ, Edwards WB, Willy RW. Optimal Load for Managing Low-Risk Tibial and Metatarsal Bone Stress Injuries in Runners: The Science Behind the Clinical Reasoning. J Orthop Sports Phys Ther. 2021;51(7):322-330. doi:10.2519/jospt.2021.9982.
8. Mosti, MP. "Maximal strength training improves bone mineral density and neuromuscular performance in young adult women." Journal of Strength & Cond Res 28, no. 10 (2014): 2935-2945.
9. Warden, SJ, Edwards, WB, & Willy, RW. (2021). Preventing bone stress injuries in runners with optimal workload. Current Osteop Reports, 19(3), 298.
10. Pouresmaeili F, Kamalidehghan B, Kamarehei M, Goh YM. A comprehensive overview on osteoporosis and its risk factors. Ther Clin Risk Manag. 2018;14:2029-2049. Published 2018 Nov 6. doi:10.2147/TCRM.S138000.
11. Papageorgiou M, Dolan E, Elliott-Sale KJ, Sale C. Reduced energy availability: implications for bone health in physically active populations. Eur J Nutr. 2018;57(3):847-859. doi:10.1007/s00394-017-1498-8
