Is it legal for not granting increment for using leaves for medical treatment ?

Company rules have to be referred for making proper opinion and oblidge.

Otherwise, what is the medical treatment for cervical spondilytis, except physio theraphy, which restrained you from attending your duty ? 

Government rules and private firm rules may be different. You can review the business's bylaws. If you are in noida and want corporate lawyer then, visit: Corporate Lawyers in Noida

Denying an increment solely due to medical leave may not be legally justified if your leave was taken under legally protected provisions such as the Employees’ State Insurance Act (ESI) or other applicable labour laws. You may review your company's leave policy, consult HR for clarification, and, if needed, seek legal advice to determine if your rights have been violated. visit Lawyer in Gurugram