Constructive terminations can be difficult to prove. Before deciding to quit your job, I highly recommend speaking with an attorney knowledgeable regarding wrongful termination litigation and disability accommodations. It is possible, based on the information you provided, that your employer has failed to reasonably accommodate your disability (this assumes, of course, that you have a "disability" as defined by federal and California discrimination laws - which is different than how workers' compensation defines "disabled.")
It is possible to work with the employer and your doctors to ensure your medical condition is being accommodated. If there are no possible accommodations at work you may need to take a temporary leave of absence while your knee heals. All these things should be discussed with an employment attorney.
If your employer refuses to honor your work restrictions, and your condition has worsened as a result of your required performance of your usual and customary job duties despite the medical restrictions, you may have a separate claim for a cumulative trama for the period you have returned to work. This is a seperate workers' compensation claim that needs to be filed.
In addition this cumulative trauma claim may involve "serious and willful misconduct" on the part of the employer (Labor Code 4553), as your injury (the worsening of this condition) was based on the deliberate action by the employer.
Please feel free to contact me if you have any further questions. .
In order to have a case for "constructive termination" you would need to show that the treatment was such that no, reasonable employee could continue to work there. You would need to provide additional information about what you believe constitutes the "emotional abuse and harassment". One thing that you should do is to document the fact that they have ignored the workers compensations restrictions and failed to accomodate any reasonable requests that your doctors had as to work restrictions. You should do this in writing and in a form that you have proof of receipt such as certified mail, email (with confirmation of receipt) or fax with confirmation of receipt.