What are the symptoms of TMD (temporomandibular disorder)?

It sounds like you have 2 issues that concern you. 1) Your lower jaw shifting to the left on opening This is usually caused by some jaw joint (temporomandibular joint, or TMJ) degeneration on the left. TMJ disease ranges from elongation and distortion of the cushioning disc found between the bony surfaces of the joint to osteoarthritis (degenerative changes of the bony joint surfaces). These changes may cause restriction in the full range of joint movement on the affected (left) side and may even be painful.

This is a common problem particularly in younger patients and we have had a number come into the Sports Clinic with these symptoms. Often it is not due to a tendon or muscle issue but comes from a scapulo-thoracic bursa. This is a potential space that sits between your shoulder blade and chest wall that allows your shoulderblad to move freely. Sometimes when inflamed, it causes cracking and pain. The first thing to do is to make sure that this is indeed th cause with a clinical assessment and maybe an ultrasound examination of the shoulder.