Weight bearing is defined as the amount of weight that may be borne on a lower extremity during standing or ambulation. In sitting the lower extremities are non-weight bearing since they do not support the body weight. In static standing each lower extremity will bear 50% of the body's weight. As you begin walking, each leg will bear 100% or full weight bearing when the opposite leg leaves the ground.
Weight bearing may be restricted depending on the medical status of the involved limb due to injury, disease or surgery. Assistive devices are used to limit the amount of weight or force that is exerted through the legs during ambulation. The following terms describe the degrees of weight bearing commonly seen in orthopedic injuries:
- Non-weight bearing (NWB) – The involved lower extremity is not allowed to contact the ground and bears none of the weight of the body during ambulation. Assistive device required – crutches or walker
- Toe touch (TTWB) or touch down weight bearing (TDWB) - The toes of the involved lower extremity are allowed to rest on the floor to assist in balancing but no weight bearing is allowed. Assistive device required – crutches or walker.
- Partial weight bearing (PWB) - Weight bearing is limited and may be up to 50% of body weight. A specific weight limit may be provided by the physician such as 20 lb. A scale is often useful to instruct the patient in maintaining the restriction. Assistive device required – crutches or walker.
- Weight bearing as tolerated (WBAT) - The patient is allowed to determine the amount of weight she feels comfortable in applying to the involved lower extremity. This may vary from very light to full weight. Assistive devices may or may not be required depending on the medical condition of the lower extremity. An assistive device may be used initially and then discarded as the patient improves. Assistive device options – crutches, walker, cane.
- Full weight bearing (FWB) - As the name implies the patient is allowed to put full weight through the involved lower extremity. An assistive device is not used to decrease weight bearing but may be used for balance.