01/22/2013 10:42 am ET Updated Mar 24, 2013

Rasheed Wallace and Stress Injuries

Rasheed Wallace, the 38 year-old forward/center, who was coaxed out of a two-year retirement to play for the NY Knicks this season, has not played since December 15th due to a stress reaction in his left foot. Wallace has a history of left foot issues, and has reportedly yet to begin running. Though he insists he will return for the 2013 campaign, some nameless members of the organization evidently fear he'll be lost for the remainder and the injury will precipitate his re-retirement.

What is a stress reaction and how does it differ from a stress fracture?
Excessive and repetitive loading on weight-bearing bones can cause what some term "fatigue damage." The milder stress reaction results in bony abnormalities that are evident with diagnostic testing (MRI, bone scans or less likely x-ray) but does not entail disruption of the cortex, the outer shell. In contrast, stress fractures progress from stage 1 to stage 3, and in each the degree of cortical cracking becomes more extensive leading ultimately to failure. Simple x-rays often do not reveal evidence of stress injuries until healing is well underway and the calcification "lights up" the area.

Which bones most commonly suffer stress reactions and stress fractures?
The small bones of the feet (metatarsals) collectively suffer the majority of stress injuries. The heel bone (calcaneus) and tibia (heavier bone of the lower leg) are also often victims of this injury.

Who typically suffers bony stress injuries?
Athletes competing in activities requiring a great deal of running, jumping or marching (military personnel) are most prone to stress injuries, with sports putting a premium on leanness, such as long distance running, dancing and gymnastics all increasing risk. Overuse and loading of the upper extremities can also result in upper body stress injuries.

Other Predisposing factors:
Those with hormonal irregularities or low bone density (osteopenia or osteoporosis) are at higher risk of developing stress responses. Athletes suffering from disordered eating (preponderantly women), are particularly prone, even in the heavier bone of the thigh (femur). Runners or other athletes with these conditions are also more likely than others to develop pubic bone or sacral area (very low back) pain due to stress fractures in these bones.

Additionally, those with very flat (pronated) feet or with very high arches (cavus feet) have an increased risk of exhibiting stress responses or stress fractures in the bones of the foot. Metabolic bone diseases as well as muscle weakness or imbalances can also predispose to stress injuries. Increased incidence has also been reported due to smoking and alcohol consumption.