American Society of Hirudotherapy

Knee Osteoarthritis

Off-label use with three RCTs showing pain and function improvement comparable to NSAID gel at 3 months in mild-to-moderate symptomatic knee OA.

Tier B — RCT-supported off-labelStudied off-labelLast updated: 2026-05-26 · Reviewed by ASH Editorial Board

Patient Summary

Is this FDA-cleared for this use?
No — investigated off-label. The FDA cleared medicinal leeches in 2004 only for venous congestion in microsurgical reconstruction (K040187). Use for knee osteoarthritis is supported by published research but not FDA-evaluated.
What evidence exists?
Several published randomized trials (Michalsen 2003, Stange 2012, Andereya 2008, İşık 2017) and a 2014 meta-analysis (Lauche et al.) suggest a moderate, short-to-medium-term reduction in knee pain compared to standard comparators such as topical NSAID gel, TENS, or a sham control. Effects have been measured out to about 3 months. The trials are mostly from research groups in Germany, all are small (under 130 patients), and longer-term outcomes (12+ months) are not well studied. This is not a substitute for proven treatments such as exercise therapy, weight management, or surgery when indicated.
Main risks
  • Bleeding and oozing from each bite site for several hours, sometimes up to 24 hours
  • Itching, redness, and irritation at the bite sites lasting days to weeks (15 to 20 percent of patients)
  • Mild anemia if many leeches are used (uncommon with a single session)
  • Local skin infection or, rarely, Aeromonas infection from leech gut bacteria
  • Allergic reaction to leech saliva (uncommon)
  • Small permanent scars at the bite sites
Who should not consider this
  • Patients taking blood thinners such as warfarin, apixaban, rivaroxaban, dabigatran, or heparin
  • Patients with hemophilia or other inherited bleeding disorders
  • Patients with severe anemia (hemoglobin under 10 g/dL)
  • Patients with a weakened immune system, especially severe neutropenia
  • Patients with an active joint infection (septic arthritis) or skin infection at the planned bite area
  • Patients within 6 months of a knee replacement surgery
  • Pregnant patients (relative caution, especially first and third trimester)
What to ask your clinician
  • Have I tried first-line treatments such as exercise therapy, weight loss, and topical or oral pain medicines, and what does my orthopedist think?
  • What is the realistic chance leech therapy will help me, and for how long?
  • What evidence does the practitioner rely on, and have they treated patients like me before?
  • Are leeches from an FDA-registered supplier and used only once?
  • What antibiotic, if any, will I be given for Aeromonas prevention?
  • What is the cost and is it covered by insurance? (typically not covered as it is off-label)
  • What is the plan if symptoms come back — repeat session, escalation to injections, or surgery referral?
When to seek urgent care
  • Bleeding from a bite site lasting more than 24 hours or soaking through dressings
  • Spreading redness, warmth, pus, red streaks, or increasing pain around the bite sites
  • Fever above 38.0 C / 100.4 F or chills
  • Sudden severe knee pain, swelling, or inability to bear weight
  • Hives, facial or tongue swelling, throat tightness, or breathing difficulty

What this does NOT mean

  • It does not mean leech therapy is FDA-approved for knee osteoarthritis — it is not.
  • It does not mean leeches cure osteoarthritis — the underlying cartilage wear continues; treatment may only reduce symptoms temporarily.
  • It does not mean leech therapy is better than exercise therapy, weight management, physiotherapy, or surgery for appropriate candidates — those remain the standards.
  • It does not mean every patient improves — the trials show meaningful improvement on average, but individual responses vary widely.
  • It does not mean a single session is enough forever — the published effect duration is mostly 3 to 6 months.

Safety cross-references

Clinical Profile

Category
musculoskeletal
ICD-10
M17.0, M17.10, M17.11, M17.12, M17.5
Safety tier
low

Evidence Summary

Randomized trials of single-session leech therapy in knee OA are consistent. Michalsen 2003 (n=51) showed WOMAC pain reduction of ~64% at day 7 vs. ~18% for topical diclofenac (P<0.001) — the largest between-group difference at day 7 — with function and stiffness benefits persisting through 3 months. Stange 2012 (n=52) found leech superior to TENS, and Andereya 2008 (n=113) confirmed benefit against a sham/placebo control. A 2014 meta-analysis (Lauche et al., Clin J Pain; 3 RCTs + 1 controlled trial, 237 patients) found strong evidence for immediate pain reduction (SMD -1.05, P<0.01). No serious adverse events; most common AE was prolonged bite-site itching (15-20%). Long-term (≥12 months) data are limited.

Treatment specifics

How many leeches, where they are placed, how long a session lasts, and whether to repeat are clinical decisions made by a qualified provider under institutional protocol — not something to self-administer. Discuss the specifics with a clinician experienced in medicinal leech therapy. (Clinicians: switch the audience selector in the top bar to “Clinician” to view protocol detail.)

Key Trials

  1. Michalsen A et al. (2003), n=51 · PMID 14597456 · ASH analysis →
  2. Stange R et al. (2012), n=113
  3. Lauche R et al. (2014), n=237 · PMID 23446069 · ASH analysis →
Sample sizes of key trials for Knee OsteoarthritisMichalsen A et al. 200351Stange R et al. 2012113Lauche R et al. 2014237
Participants per key trial (n). Larger trials generally carry more statistical weight; case series with unspecified counts are omitted.
Study-design composition of the evidence base for Knee Osteoarthritis3studies
  • RCT: 2 (67%)
  • Meta Analysis: 1 (33%)
Composition of the cited evidence base by study design, from strongest (meta-analysis, systematic review) to weakest (case report). A base weighted toward RCTs and reviews is more reliable.

Detailed Trial Entries

30 trials indexed in the ASH RCT Library with full Study Profile, GRADE rating, and clinical implications:

Forest plot — Cohen's d effect sizes across 11 trials
Cohen's d (pain or primary endpoint)Michalsen A 20031.40 (n=51)Andereya S 20061.10 (n=24)Andereya S 20080.95 (n=113)Lauche R 20140.86 (n=52)Stange R 20120.78 (n=50)Khoshnevisan A 20220.89 (n=80)Sarbaev IS 20190.63 (n=96)Karandikar S 20180.58 (n=60)Cui Y 20240.04 (n=144)Zaidi SM 20090.65 (n=30)American Society of Hirudotherapy Clinical Investigators 20240.82 (n=45)-0.5-0.10.20.60.91.31.6← Favors controlFavors intervention →

Point size proportional to sample size. Positive values favor leech therapy; vertical line = no effect. Cohen's d > 0.8 = large effect; 0.5–0.8 = medium; 0.2–0.5 = small; < 0.2 = negligible.

Contraindications

  • Active anticoagulant therapy (warfarin INR >2.0, DOACs, heparin)
  • Hemophilia or other bleeding disorder
  • Severe anemia (Hb <10 g/dL)
  • Active bacteremia or sepsis
  • Known hypersensitivity to leech salivary proteins
  • Pregnancy (relative — first/third trimester)
  • Immunocompromised state with severe neutropenia
  • Acute septic arthritis
  • Knee replacement (within 6 months)

Related Conditions

Thumb Carpometacarpal (CMC-1) Osteoarthritis

Off-label use with RCT evidence: single-session leech therapy reduces pain and improves function in CMC-1 (basal thumb) OA at 8 weeks.

Lateral Epicondylitis (Tennis Elbow)

Off-label use with two RCTs showing significant pain reduction at 7-12 weeks compared to topical NSAID and conventional physiotherapy.

Plantar Fasciitis

Off-label use with one RCT showing significant heel pain reduction at 6 weeks compared to conservative care.

Fibromyalgia

Investigational adjunctive use; one small pilot suggests transient improvement in tender-point and quality-of-life scores. Not a primary treatment.

Explore the evidence base

This website provides educational information and does not constitute medical advice, diagnosis, or treatment recommendations. Medicinal leech therapy carries clinically meaningful risks and should be performed only by qualified clinicians under institutionally approved protocols. FDA 510(k) clearance for medicinal leeches is limited to specific indications; investigational and off-label discussions are labeled accordingly. For patient-specific guidance, consult a qualified healthcare provider.

Knee Osteoarthritis — Hirudotherapy Evidence | ASH