Texas workers' compensation law defines disability as the inability, because of a workplace injury, to earn the pre-injury wage. This means that if your injury results in a loss of earnings, then you meet the definition of disability. This might be because you cannot work at all af ter your injury. Maybe you can work but not full time, so you get paid less than before your injury. Sometimes injured workers are given different job duties after an injury, and it comes with less pay. In all of these situations, you would have disability.
You can see, then, that disability is not what people generally consider the word "disabled" to mean. Disability in a Texas workers' comp claim is different than disability in a social security claim. It is not necessarily about functional ability, but more about earning ability. It is an economic issue, not a medical opinion.
There are many scenarios that result in disability. The majority of disability cases involve an inability to work at all (like the traditional concept of disability) or a release to return to work on light duty. If you cannot work at all, then you obviously can't earn wages - that's disability. If your employer won't let you work light duty, then your injury is the reason why you aren't earning wages - that's disability. You will have to prove that you have disability in order to be entitled to temporary income benefits. Generally, injured workers can prove disability by providing a DWC-73 - a work status report - from a doctor. This form documents your functional ability. If it says you cannot work at all, that is evidence of disability. The same is true if it documents the various restrictions you might have that would keep you from being able to do your regular job duties. Other evidence that might be considered would be diagnostic test results (MRI, EMG, x-rays), surgical records and other medical opinions about your physical condition and functional ability, as well as your job description.
This is a general overview of the concept of disability. It is sometimes a very complicated and multi-faceted question. But if you can't work because of your injury, it is often the most important question.