Anatomical Locations for Trigger Point Injections
Trigger point injections are administered directly into palpable myofascial trigger points—discrete, hyperirritable nodules within taut bands of skeletal muscle that produce focal tenderness, restricted range of motion, and a local twitch response upon needle stimulation. 1
Specific Anatomical Sites by Condition
Myofascial Pain Syndrome
- Trapezius muscle: Upper, middle, and lower fibers are common injection sites for shoulder girdle and neck pain 2, 3, 4
- Deltoid muscle: Lateral shoulder region for upper extremity myofascial pain 4
- Infraspinatus and teres major muscles: Lateral scapular area for posterior shoulder pain 4
- Paraspinal muscles: Lumbar region for low-back pain, targeting palpable trigger points with focal tenderness 1
- Temporal muscles: For patients with masticatory myofascial pain and associated headaches 5
Tension Headaches
- Temporal muscles: Bilateral injections for tension-type headaches associated with myofascial trigger points 5
- Upper trapezius and cervical paraspinal muscles: For cervicogenic headaches with myofascial component 2, 3
Fibromyalgia
- Upper trapezius muscle: Most commonly studied site, though response is delayed and attenuated compared to isolated myofascial pain 6
- Any muscle with active trigger points: Identified by focal tenderness on palpation, restricted stretch range of motion, and local twitch response 1
Clinical Identification of Injection Sites
The precise location is determined by physical examination findings, not predetermined anatomical landmarks. 1
Diagnostic Criteria for Active Trigger Points
- Focal tenderness on palpation: Discrete point of maximum tenderness within muscle 1
- Palpable taut band: Rope-like consistency within muscle tissue 1
- Local twitch response: Visible or palpable contraction upon needle stimulation 1
- Restricted range of motion: Limited stretch in affected muscle 1
- Referred pain pattern: Pain radiating from trigger point in characteristic distribution 1
Technical Considerations
Image Guidance
- Ultrasound guidance is increasingly recommended to improve accuracy and safety, particularly for deeper muscles like infraspinatus and teres major 7, 4
- Fluoroscopy may be used for certain anatomical locations, though not routinely required for superficial trigger points 7
Multi-Site Injections
- Multiple trigger points can be injected in a single session using layer-by-layer technique under ultrasound guidance 4
- The "3-in-1" technique allows treatment of deltoid, infraspinatus, and teres major muscles within the same sonographic view 4
Important Clinical Caveats
Fibromyalgia-Specific Considerations
- Patients with both fibromyalgia and myofascial pain experience significantly more postinjection soreness that develops sooner and lasts longer than patients with isolated myofascial pain 6
- Pain relief is delayed and attenuated in fibromyalgia patients compared to those with isolated myofascial pain syndrome 6
- Immediate effectiveness is significantly reduced in fibromyalgia patients, though 2-week outcomes show similar improvement in pain threshold and range of motion 6
Frequency Limitations
- Injections should not be repeated more frequently than once every 2 months once therapeutic effect is achieved 2
- Maximum of 4 sets of injections should be considered; additional injections are not medically necessary without documented clinical response 2
- Quantifiable improvement in pain scores, function, and duration of relief must be documented to justify repeat injections 2
Treatment Context
- Trigger point injections provide only temporary relief and should be part of multimodal treatment including physical therapy, stretching, and strengthening exercises 1, 2
- Conservative measures should be attempted first before proceeding to injection therapy 2
- Dry needling may be equally effective as injections containing local anesthetics or steroids 1, 2