As a runner, it’s common to experience aches, pains and tightness from time to time. However, when these symptoms are persistent, it raises suspicion that something more sinister could be going on.
One particular area of concern is the front of the hip, where symptoms are commonly attributed to having tight hip flexors. As a result, the first port of call is usually to stretch the area. This might provide some temporary relief, but the feeling often comes back. So, what else could be going on?
One common site for a bone stress injury is the neck of the femur. I’ve personally had two patients over the last 12 months present with this very pattern of symptoms. Of course, there are other potential sites of bone stress injury in this region (e.g. pubic ramus and the greater and lesser trochanteric regions), as well as other diagnoses to consider (e.g. labral tears, FAI, bursitis and tendinopathy).
So, what are some of the key things we look for when trying to pick up these injuries? A lot of the clues come from the patient’s history and some key objective findings.
Screenshot from Nathan’s Strava.
Single-leg hopping is sometimes used as part of a bone stress injury assessment. However, it still places considerable load through the femoral neck, so it is not something I’d recommend performing if there is already a strong suspicion of a high-risk injury. We don’t want to risk aggravating a potential fracture just to reproduce the symptoms!
If there is suspicion of a bone stress injury, it should be treated as such until proven otherwise.
In particular, if a femoral neck stress injury is suspected, running should cease immediately and weight-bearing should be protected while awaiting appropriate medical assessment. Depending on the clinical presentation, this may mean using crutches and arranging urgent medical or orthopaedic review.
The first step in imaging is generally an X-ray, although these can often appear normal in the early stages of a bone stress injury. If clinical suspicion remains, an MRI is the gold-standard investigation for identifying and classifying these injuries. It will either rule out bone stress (awesome!) or provide important details about the location and severity of the injury, giving us a much clearer picture of how it should be managed.
Let me run you through some of the key distinctions we make when looking at the imaging.
Compressive-sided bone stress injuries affect the underside (inferior aspect) of the femoral neck. This is generally the better of two not-so-great situations, as incomplete compression-sided injuries are often classified as lower risk. They generally have good healing potential and can frequently be managed conservatively, although weight-bearing restrictions may still be required depending on the extent of the injury.
Tension-sided bone stress injuries affect the upper (superior) aspect of the femoral neck. These are considered high-risk because they can progress to become complete or displaced fractures, which obviously isn’t great! Due to the tensile forces acting across this part of the bone, these injuries have a poorer healing environment and are more prone to progression.
Think about bending a banana: the tension on the top side of the banana pulls the two sides apart, whereas the compression on the bottom side pushes them together. It’s a similar concept with the femoral neck.
These injuries warrant prompt orthopaedic assessment, as surgical fixation is often recommended depending on the fracture configuration and severity. A displaced femoral neck fracture is a particularly serious complication that we want to avoid.
Now, let’s look at the different grades of bone stress injuries on MRI.
The following is a commonly used four-grade MRI classification (Nattiv et al.):
Grade 1 – Mild bone marrow or periosteal oedema (swelling around the bone) visible on T2-weighted images, with a normal T1-weighted image.
Grade 2 – Moderate bone marrow or periosteal oedema on T2-weighted images, with a normal T1-weighted image.
Grade 3 – Severe bone marrow oedema visible on both T1- and T2-weighted images, without a definite fracture line.
Grade 4 – Grade 3 findings, in addition to a visible fracture line.
Pictured: Grade 4 bone stress injury (stress fracture) on the compression side. Source: radiopaedia
As you can see, there is quite a lot to consider when diagnosing these injuries. Understanding the location, extent and severity is important, as this will ultimately dictate how we approach management.
It’s also important to remember that MRI grading is only one part of the picture. With femoral neck injuries, the location of the injury (compression vs tension-sided), the extent of any fracture line and whether there is any displacement are particularly important when determining treatment.
Treatment generally starts with identifying what caused the injury in the first place. Sometimes, further referrals may be required to investigate things such as bone density or blood markers to identify other potential contributing factors. A dietitian may also be helpful in addressing potential under-fuelling and recovery issues.
In particular, we need to consider whether the athlete is consuming enough energy to support their training demands, as well as other potential contributors to reduced bone health. This can include inadequate calcium or vitamin D intake, hormonal disturbances, menstrual irregularities and underlying medical conditions.
If everything from that perspective checks out, we then dive deeper into the biomechanical and training-related factors that may have contributed to the overload.
We aim to identify any impairments that could have increased the load through the hip, such as mobility deficits at the ankles or strength deficits in the calves, quads, glutes or hamstrings.
Pictured: Our dynamometry testing completed in the clinic which identified a 13% difference between sides in quadriceps strength.
There may be a period where weight-bearing needs to be restricted or modified, but we can work around this to maintain or build strength and mobility wherever possible. The priority, however, is allowing the bone to heal safely.
From there, we establish a graded loading program. This generally starts with appropriate resistance exercises before progressing through to more demanding functional activities, jumping and landing, and eventually back to running. Running typically starts with run-walk intervals before gradually building back towards full training volume.
This is a process that takes months rather than weeks. As a general guide, return to running following a femoral neck bone stress injury can take anywhere from around 3–6 months or longer. The timeframe is highly dependent on the severity and location of the injury, whether surgery is required and how the bone responds to treatment.
Importantly, progression isn’t dictated by time alone. We need to consider clinical symptoms, evidence of bone healing where appropriate, functional capacity and, particularly following surgical management, clearance from the treating orthopaedic surgeon.
As you can see, these are complex injuries with lots of moving parts, contributing factors and considerations when it comes to treatment.
The biggest takeaway is that persistent anterior hip or groin pain in runners shouldn’t automatically be dismissed as tight hip flexors. If symptoms are recurring, worsening or starting to affect everyday activities, it’s worth getting them assessed rather than continuing to stretch or run through them.
Femoral neck bone stress injuries are particularly important to identify early, as delayed diagnosis can result in fracture progression and potentially significant complications.
Seeing someone with experience managing these injuries is important for achieving an early and accurate diagnosis and getting you on the right road to recovery.
So, if you’re experiencing persistent hip flexor or groin tightness that just doesn’t seem to go away, don’t automatically assume it’s just a tight muscle!
If you have any questions or concerns about any of this, please get in touch!
