I found this on the web.
OFF ROAD MOUNTAIN BIKING is now an extremely popular recreation and a potent cause of serious injury. To establish the morbidity associated with this sport, data were collected prospectively over one year on all patients presenting with an injury caused by either recreational or competitive off road mountain biking.
Eighty four patients were identified, 70 males and 14 females, with a mean age of 22.5 years (range 8?71). Most accidents occurred during the summer months, most commonly in August. Each patient had an average of 1.6 injuries (n = 133) and these were divided into 15 categories, ranging from minor soft tissue to potentially life threatening. Operative intervention was indicated for 19 patients (23%) and several required multiple procedures.
The commonest injuries were clavicle fractures (13%), shoulder injuries (12%), and distal radial fractures (11%). However, of a more sinister nature, one patient had a C2/3 dislocation requiring urgent stabilization, one required a chest drain for a hemo-pneumothorax, and another required an emergency and life saving nephrectomy.
Always be careful out there!