A Metatarsal Stress Fracture (MSF) is a common overuse injury experienced by people engaged in high impact sports in which chronic, repetitive forces acting on a metatarsal (MT) give rise to the formation of a small, thin crack (fracture). This condition most often affects the 2nd and 3rd MT, although it can sometimes affect others, such as the 5th MT in the picture above. MSF have also been called “March fractures” as they are common in army recruits. MSFs are different to acute fractures following a traumatic event because they arise from repeated stresses over long periods of time (e.g. running or marching) rather than a single event (e.g. a horse standing on your foot).
The symptoms of an MSF include:
- Gradual onset of mild to severe pain affecting the mid-foot and forefoot.
- Pain is better for rest and worsened by weight-bearing.
- May be accompanied by swelling of the local area.
MSFs have a few common causes:
- Overuse during high impact activities: e.g. marching and long-distance running.
- Overpronation (flexible, low arched or flat feet): when the foot rolls in and flattens the inside (medial) arch, the 2nd, 3rd and 4th MTs are put under a great deal of stress.
- Oversupination (rigid, high arched feet): supinated foot types are generally poor shock absorbers and the repeated forces acting on the foot can lead to fractures.
- A long or plantarflexed MT (often affecting the 2nd MT).
- Poor footwear choices.
- Sudden changes in surface (e.g. runner changing from a treadmill to road running).
- Sudden increase in activity (e.g. training for a first marathon attempt).
A podiatrist can diagnose possible an MSF by taking a thorough history of the condition and through examination and palpation of the affected area. X-rays are not a reliable means of diagnosing an MSF in the early stages (less than 2-3 weeks) as the fracture does often not show until after this time. After 3 weeks, X-Rays can be used to confirm the diagnosis.
A podiatrist would treat an MSF with the following methods:
- Rest and a reduction in weight-bearing activity for a while. Sadly, putting stress on a fractured MT will only prolong the healing process and may lead to a worsening of the condition.
- Correcting any underlying abnormal foot mechanics using functional foot orthoses (“medical grade insoles”). These abnormal mechanics lead to overpronation, insufficient pronation, and tissue stress that leads to and interferes with the healing of MSFs. Orthoses can also offload the affect MT, thereby reducing the stress on the structure.
- Providing soft-tissue rehabilitation exercises at the appropriate times to address the involvement of weak or tight muscles leading to abnormal foot mechanics or gait.
- Offering footwear advice.
In most cases, and with favourable conditions, it takes approximately 6-8 weeks for an MSF to heal, although more serious fractures can take longer. Not reducing high-impact activities sufficiently after the injury arises can cause a delay in healing and recover, or perhaps may worsen the condition. Returning to these activities too soon or at the same intensity as immediately before the injury, without a gradual increase in activity, can put the person at risk of reinjury.