To see if there is there any difference in the treatment outcomes/results such as changes in pain intensity in patients with myofascial pain who have been treated with trigger point injections or twin block?

Most treatment approaches for chronic myofascial pain are not evidence-based. Studies are usually controversial. Most are short-term, non-randomized. An essential limitation has been the lack of standardization of diagnosis. Some studies do not differentiate between joint pain and muscle pain, which can significantly affect the outcome of the treatment provided.

Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) was recently published and validated. Their protocol allows standardization of the assessment and diagnosis of patients with temporomandibular disorder, including myofascial pain.

To the investigator's knowledge, no previous prospective, randomized study has been conducted demonstrating the treatment outcomes of either trigger point injections or twin block in patients with chronic myofascial pain.

Inclusion Criteria:

• Patients diagnosed with Myofascial pain with referral based on the DC/TMD criteria
• Pain on the masseter and or temporalis muscles
• Pain present for at least 3 months

Exclusion Criteria:

• Generalized muscle disorder such as fibromyalgia
• Subjects on chronic pain medication
• Subjects who are known to have hypersensitivity to the local anesthetics.
• Pregnant women. A pregnancy test will not be given before subject enrollment. Women of childbearing ages will be asked verbally if they are pregnant. If they are unsure, then they will be excluded from the study.
• Subjects with cognitive problems e.g. Alzheimer's disease.