White Willow Bark

• NSAID-like mechanism. Willow bark contains salicin, which is converted to salicylic acid in the body. This inhibits prostaglandin synthesis (via COX enzymes) and reduces inflammatory pain—similar in principle to aspirin/NSAIDs. Reviews also note polyphenols/flavonoids that may contribute to anti-inflammatory effects. Drugs.com
• Use in musculoskeletal pain (indirect rationale). Authoritative overviews list willow bark as used for inflammatory musculoskeletal conditions (e.g., bursitis/tendinitis) based on traditional use and its analgesic pharmacology; however, they emphasize the evidence base is stronger for low-back pain than for tendon disorders. NCCIH

The anti-inflammatory/analgesic mechanism is relevant to tendon pain, but effectiveness for tendonitis specifically has not been proven in high-quality trials.

Choose a standardized product. Look for extracts standardized to a known salicin content (many products are ~15% salicin). Pharmacopoeial monographs define minimum salicylate content for quality. uspbpep.com

Dose (by salicin, not bark grams). The most commonly studied oral intake for pain is 120–240 mg salicin per day, divided 1–2 doses, typically up to 6 weeks. Start at the low end to assess tolerance. WebMD

Example label math. A capsule with 240 mg extract at 15% salicin ≈ 36 mg salicin; reaching 120–240 mg/day would be ≈ 3–7 caps/day, split doses. (Adjust to your actual label.) Source for standardization context: pharmacopeial/clinical notes. uspbpep.com

Timing & expectations. In back-pain trials, benefit appeared over days to a few weeks; it is not an instant analgesic like ibuprofen. If no improvement after 1–2 weeks, reassess. The American Journal of Medicine

Forms to avoid for dosing accuracy. Teas/tinctures can vary widely in salicin per serving, making it hard to hit evidence-based salicin targets; standardized capsules/tablets are easier to dose. (General quality guidance.) uspbpep.com

Use it as an adjunct, not a cure. For tendonitis, combine pain control with rehab basics (relative rest, gradual loading, eccentric exercises) because analgesics alone don’t restore tendon capacity. (General clinical principle; no tendonitis-specific willow data.)

There are no high-quality RCTs specifically for tendonitis. Evidence is from adjacent conditions:

• Chronic low-back pain RCT (dose-finding). 210 adults randomized to willow bark extract providing 120 mg or 240 mg salicin/day vs placebo for 4 weeks. Higher-dose groups had greater pain relief and less rescue analgesic use than placebo. The American Journal of Medicine
• Open randomized comparison (willow extract vs rofecoxib) in acute low-back pain. Suggested comparable effectiveness, though study was open-label and thus lower quality. Oxford Academic
• Systematic/umbrella evidence. Reviews highlight benefit signals for low-back pain (short-term) but emphasize limited trial numbers and call for better studies; long-term safety/efficacy data are insufficient. Cochrane
• Arthritis meta-analysis (adjacent indication). Summarizes RCTs of willow bark in arthritis populations, suggesting analgesic effects but with heterogeneity and modest quality. MDPI

Summary: Evidence supports willow bark for some short-term musculoskeletal pain (especially low-back pain). It does not prove efficacy for tendonitis, so any use for tendon pain is extrapolated, not established.