Traumatic brain injury causes unpredictable errors in the patient's gait by introducing varying mixtures of spasticity, contractures, primitive flexion and extension synergies, and impaired selective control. Surgical release or transfer of the offending muscles can improve the patient's ability to walk if functional errors have been accurately identified. While clinical testing is inadequate, instrumented motion analysis and dynamic electromyography can supply an accurate definition of the abnormalities in muscle action and provide guidelines for distinguishing local from referred motion errors. Examples of the diagnostic differences related to the equinovarus foot and the common types of knee dysfunction are presented.