Stress Fractures
Stress fractures of the foot and ankle are small cracks in the bone caused by repetitive submaximal mechanical stressthat overwhelms the bone's normal capacity to repair itself. They are common overuse injuries, particularly in athletes and military recruits.
Aetiology and Pathomechanics
The development of a stress fracture results from an imbalance between bone resorption and bone formation (remodeling) due to repeated loading.
Aetiology (Causes and Risk Factors)
Stress fractures are typically classified into two main types based on the underlying cause:
Fatigue Fracture: Occurs when normal bone is subjected to abnormal, excessive, and repetitive mechanical stress. This is the most common type and is seen in activities like running and jumping.
Insufficiency Fracture: Occurs when abnormal, weakened bone is subjected to normal mechanical stress. This can be due to conditions that decrease bone density, such as osteoporosis or hormonal imbalances.
Key risk factors are often categorized as extrinsic (external to the body) and intrinsic (related to the individual's body):
| Category | Examples of Risk Factors |
| Extrinsic | Abrupt increase in the frequency, duration, or intensity of activity (the most common cause). |
| Inappropriate equipment (e.g., worn-out or unsupportive footwear). | |
| Training surface (e.g., switching from a soft to a hard surface). | |
| Training technique or improper form. | |
| Intrinsic | Biomechanical factors (e.g., abnormal foot arch like flat feet or high arches, leg length discrepancy, muscle fatigue/imbalance). |
| Nutritional deficiencies (e.g., low Calcium or Vitamin D). | |
| Hormonal factors (e.g., the Female Athlete Triad: low energy availability, menstrual dysfunction, and low bone mineral density). | |
| Low bone density (osteoporosis or osteopenia). | |
| Previous stress fracture. |
Pathomechanics
The mechanism involves the body's natural response to stress (Wolff's Law), which dictates that bone remodels to adapt to loads.
Repetitive Microdamage: Repetitive, high-impact force creates microscopic damage (microcracks) in the bone structure.
Overwhelmed Remodeling: The bone initiates a remodeling cycle where old, damaged bone is resorbed by osteoclasts, and new bone is laid down by osteoblasts.
Imbalance: If the repetitive stress continues without adequate rest, the rate of bone resorption (breaking down old bone) exceeds the rate of new bone formation. This creates a temporary zone of weakened bone.
Fracture Formation: Continued loading on this weakened area causes the microcracks to accumulate and coalesce, eventually leading to a focal point of failure—the stress fracture (a hairline crack)
. 5. Muscle Fatigue: A contributing biomechanical factor is that muscle fatigue reduces the muscle's ability to absorb shock and support the skeleton, thereby transferring more of the impact force directly to the bone.
General Treatment
The general management of a stress fracture focuses on removing the stress that caused the injury to allow the bone to heal and then gradually returning to activity while correcting underlying risk factors.
Non-Surgical Management (Primary Treatment)
Most stress fractures are treated conservatively and heal without surgery.
Rest and Activity Modification: This is the most critical step. The individual must stop the activity that caused the pain. This period of rest usually lasts 6 to 8 weeks or until the patient is pain-free, but varies based on the fracture location. Low-impact, cross-training activities (e.g., swimming, cycling) are encouraged to maintain fitness.
Immobilization and Reduced Weight-Bearing: Depending on the severity and location, a doctor may recommend:
Protective Footwear: A stiff-soled shoe, wooden-soled sandal, or a removable walking boot/brace to reduce stress.
Crutches or a non-weight-bearing period may be necessary for painful or "high-risk" fractures (e.g., navicular, fifth metatarsal base).
Symptom Management:
RICE Protocol: Rest, Ice (for swelling), Compression, and Elevation.
Pain Relief: Acetaminophen (paracetamol) is often preferred, as there is some evidence that Nonsteroidal Anti-inflammatory Drugs (NSAIDs) like ibuprofen may interfere with bone healing, though this is debated.
Correction of Risk Factors: This is vital for prevention of recurrence and includes:
Biomechanical Assessment: Using custom orthotics to correct abnormal foot mechanics (pronation or supination).
Nutritional Support: Ensuring adequate Calcium and Vitamin D intake.
Physical Therapy: Strengthening and flexibility exercises, especially for muscles around the ankle and foot, to improve shock absorption and address muscle imbalance.
Gradual Return to Activity: Once the patient is pain-free and cleared by a physician, a slow, controlled return to previous activity is initiated. A common guideline is to increase activity (mileage, time) by no more than 10% per week.
Surgical Management
Surgery is typically reserved for high-risk stress fractures (e.g., certain navicular, fifth metatarsal, or medial malleolus fractures) that have a poor natural blood supply, fractures that fail to heal (non-union) after a sufficient period of conservative treatment, or for elite athletes where faster, more definitive fixation is desired.
Internal Fixation: Procedures may involve placing screws, pins, or plates to stabilize the bone and promote healing.