Stress Fracture return to activity

First order: 25 Year old female. Jabbing pain along the distal shaft of the tibia. Patient says it gets up to a 6/10, average is a 1-2/10. Provocative is running, jumping, going down stairs. Rest is palliative.

Second order: Pain started 3 months ago after starting crossfit, specifically after a double under clinic. Symptoms were getting better but any time she runs in her workouts, it flares up. She currently does crossfit 3 days a week. Patient is also an ultimate frisbee player who would play/practice 3-4 days/week even prior to starting crossfit.

Pain is there at the beginning of activity, get numb after “warming up”, then be really sore the next day with loading.

Physical exam: There is a two inch tender area along the distal shaft of the femur.

Dorsiflexion was 6″ Bilaterally with mild stretching. PK test was full range with mild stretching. Patient could achieve full lock out with two legs, but was limited with 1 on both sides.

Diagnosis:

1) Stress fracture of the tibia

2) Weakness of the deep calf muscles

Patient was instructed to avoid all running, jumping, and impact activities for 2 weeks. Patient was also given the single leg calf raise exercise to strengthen the deep calf muscles.

I have 2 concerns:

1) Should I be more concerned that a 25 year old female who was already participating in physical activity is getting symptoms like this when she has such good function? Should I be considering diet, metabolic, etc?

2) How do I progress this patient back into impact activities. Do I take into account her pre-injury activity level? Or do I start her at an absolute minimal amount of loading and slowly progress?