Stress fractures occur most frequently in the shin bone (tibia), foot (metatarsal), and hip (femur or pelvis). For new runners, cardiovascular fitness comes after 10 weeks whereas bone fitness requires 10 months. Stress fractures are a result of the bone not adapting fast enough for the increased stresses put on it.
Contributing factors
- Female (12 times more likely)
- Amenorrhea (6 times more likely)
- Low dietary calcium (8 times more likely, best predictor)
- Low bone density
- Race (Caucasian)
- Leg length inequality (73% in long leg: femur, tibia, metatarsal; 60% in short leg: fibula)
- Beginners
- Competitive (female)
- Over pronation
- Muscle imbalance (weakness)
- Training errors
Symptoms
The pain comes on suddenly and there is no history of trauma. Persistent pain and local tenderness, even after rest, ice and decreased training is suggestive of stress fracture. Hopping on the injured leg is painful and running is unbearable. Tibial stress fractures can mimic shin splints and is often incorrectly diagnosed. With continued running, this problem can lead to a complete fracture.
X-rays will usually not show any signs of a fracture (57% are negative in the first 3 weeks). A bone scan will show increased activity (hot spot) where there is an active repair process of the bone presently underway. CT scan is best to visualize the small bones of the foot.
Treatment
- Rest
- Restricted weight bearing (pneumatic leg brace)
- Alternate activity (pool running)
- Orthotics (foot mechanics)
- Evaluate footwear
- Identify and address training errors
Most stress fractures will heal after 6-8 weeks depending on the site (longer for the bones higher up the leg). Continuation of activity to a complete fracture will require 6-8 months of rest. This is a longer healing time than a regular fracture (6-8 weeks) because the blood supply and hence the healing ability of the bone is compromised.