Why can't i open my jaw with an ear infection?

TMJ involvement : There could be several possibilities. If you have clinically been diagnosed with an ear infection by an ENT physician . Then it could be extension of the infection into the jaw joint or you could be clenching or grinding your teeth secondary to the discomfort your having causing jaw muscle spasm. Suggest you contact an oral surgeon for an evaluation.

The ear canal : Is in immediate proximity , posterior-superiorly , (although separated by a bony wall deeper within) to the tm joint and also why with patients who have TMJ dysfunction have exaggerated pain on opening when a finger is placed within external ear canal and pressed forward.

2 possibilities: 1) you have an ear infection and the ear swelling involves the adjacent TMJ apparatus. This should resolve as the infection resolves with antibiotics. 2) you have a TMJ problem, with secondary ear pain. Your MD looks in the ear, doesn't see anything. Rather than admitting he doesn't see anything, proclaims "ear infection" and prescribes antibiotics. My guess is #2. If so, see a TMJ expert.