What does knee stabilization mean?
"Knee stabilization" means that the muscles surrounding the joint are strong enough to allow the knee to perform controlled, precise movements in all positions — the joint does not "wobble" and the cartilage is not exposed to unnecessary loading. Achieving this goal can be effectively supported with home NMES stimulation.
Key idea
The knee has dual stability: passive (bones + ligaments) and active (muscles). The active stabilizing system — especially the quadriceps — acts as a "living orthosis." Its weakening can increase cartilage load and cause pain. According to clinical studies, the combination of NMES + active training can substantially improve quadriceps strength and knee function in postoperative, sports-injury and osteoarthritis situations.1,4
Why should you stabilize your knee? – Anatomy and biomechanics for non-experts
The knee is the body's largest joint and one of the most heavily loaded. On an active day you may take 8–10,000 steps. During walking, peak forces in the knee can reach 2–3 times your body weight. On stairs this is typically around three times, but in some situations it can be higher. During running and movements with deep knee flexion — for example deep squats — peak joint loading can reach forces equivalent to 5–8 times body weight. For an 80 kg person this can correspond in extreme cases to approximately 400–600 kg of internal compressive force. This is not actual external mass, but the internal joint force that arises from the combined effects of muscles, body weight, speed of motion and joint position.
The knee is the meeting point of three bones:
- Femur (thigh bone) – its distal end
- Tibia (shin bone) – its proximal end
- Patella (kneecap) – at the front, acting like a "pulley" on the quadriceps tendon path
Between the bones are two cushioning cartilages (the medial and lateral menisci) that dampen impact. Four main ligaments hold the bones: two collateral ligaments (MCL, LCL) and two cruciate ligaments (ACL anterior, PCL posterior). The joint is enclosed by the joint capsule, containing synovial fluid.
The knee has a dual stabilizing system:
- Passive stability: provided by bony surfaces + ligaments. This is "static" — it does not adapt to movement and does not protect well against sudden lateral forces.
- Active (dynamic) stability: provided by the muscles around the joint. This is "intelligent" — it adapts moment-to-moment to movement and dampens shock like a car's suspension.
The active stabilizing muscles are grouped into three:
- Quadriceps (thigh extensors, 4 muscles): located on the front of the thigh, responsible for knee extension and guiding the patella. Key muscle for knee stability.
- Hamstrings (thigh flexors, 3 muscles): located on the back of the thigh, responsible for knee flexion. Together with the quadriceps they stabilize in a "sandwich" manner.
- Calf (gastrocnemius, soleus): contributes to the lower-posterior stability of the knee.
When your muscles are weak, the knee "does not get the proper orthotic support" — the load concentrates on the cartilage and bones. This is a "vicious cycle":
- Weak quadriceps → inaccurate, uncontrolled knee movement
- Inaccurate movement → unnecessary loading of the cartilage
- Loaded cartilage → pain and inflammation
- Because of pain you use the leg less → muscles weaken further
- You return to point 1 — in a worse condition
Clinical literature clearly links quadriceps weakness with worsening knee joint loading and osteoarthritis progression, especially after ACL surgery.8 This is why quadriceps strengthening is a priority in knee rehabilitation.
When is knee stabilization especially important?
Home NMES training can be particularly valuable in the following situations:
Six weeks of preoperative NMES training before knee replacement surgery has been shown in clinical trials to improve preoperative functional status (WOMAC, KOOS), which indirectly facilitates postoperative rehabilitation.7 Better pre-op muscle strength predicts faster recovery.
After surgery the quadriceps can become "switched off" — muscle strength can decrease by 50–60% in the early weeks. A meta-analysis of 9 RCTs found that NMES + standard rehab provides significant improvements in quadriceps strength at 1, 3–4 and 12–13 months, and reduces pain and improves gait ability.1 A 2022 RCT (home app-controlled NMES) reported statistically significant improvements at 3, 6 and 12 weeks compared with control.2
After ACL reconstruction, NMES has been shown in clinical trials to significantly improve quadriceps and hamstring strength and limb load-symmetry — both short-term (≤6 weeks) and long-term (~1 year). Early NMES (starting in the first postoperative week) is particularly effective.3,8
A 2024 RCT found that in 75 patients with knee osteoarthritis the combination of NMES + exercise produced meaningful improvements over 12 weeks in VMO thickness, knee range of motion, and WOMAC stiffness and function scores — better than exercise or NMES alone.4
Realistic expectation: a 2023 meta-analysis concluded that NMES + exercise is not significantly better for pain reduction than exercise alone.5 Thus NMES is not primarily for immediate pain relief, but for improving muscle structure — which may indirectly reduce pain.
In a 130-participant RCT for patellar pain, NMES + home exercise resulted in greater improvement in quadriceps strength over 9 weeks than home exercise alone.6 It is particularly worth trying in active young adults (runners, athletes).
For athletes, NMES can be an adjunct to classic training. Targeted quadriceps training relates to both knee injury prevention and performance improvement. The Globus sport device family is specifically designed for this purpose.
Preparations
Before you start treatment, prepare the equipment:
- Take out your device, four cables and the self-adhesive electrode pads.
- You can choose from several electrode sizes:
- Only 5×5 cm square electrode pads for all positions, OR
- 5×5 on the motor point and a higher 5×9 cm pad on the muscle, OR
- 5×5 on the motor point and a higher 5×9 cm dual electrode.
- You can buy self-adhesive electrode pads here.
- For muscle stimulation use the colored cables. It does not matter which colored cable goes into which connector — the colors only help you identify the two ends of a cable.
- Plug one end into your device. If you start with a single cable, begin with Output 1 (front left).
- The other end of the cable splits and ends in pin-like metal connectors. Attach one self-adhesive electrode pad to each and stick them to your bare skin as shown in the illustration.
- The two electrode pads belonging to the same colored cable must be on the same muscle (or muscle group). Therapeutic current will flow between the two pads — this triggers the contraction.
INCORRECT setup!
It is NOT correct if the two electrodes are NOT on the same muscle, or are more than about a handspan (≈20 cm) apart.
Electrode placement points
- For treatment, remove the self-adhesive electrode pads from their plastic backing and stick them to your skin.
- It is advisable to first wash your skin with lukewarm soapy water and dry it.
- The greasier, dirtier or sweatier your skin is, the shorter the usable life of the same electrode pad.
- Take the cable connected to Output 1 and place its two electrode pads one below the other as shown in the illustration.
- Apply the electrode pads for Outputs 2, 3 and 4 in order according to the illustration.
Quadriceps re-strengthening – 12-week training plan
If you have an Elite, Elite 150, Cycling Pro, Runner Pro, Triathlon Pro, Soccer Pro, Moto Pro, Premium 400, Activa 700 or The Champion device, follow the sport protocol below.
The programs can be found in the Program List / Sport program group. Always select the Lower limbs muscle group!
Week 1 – Introduction (acclimatization)
| Program | Mon | Tue | Wed | Thu | Fri | Sat | Sun |
|---|---|---|---|---|---|---|---|
| Stiffness relief (20 minutes) | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| Endurance strength (25 minutes) | ✓ | ✓ | ✓ | ✓ |
Weeks 2–3 – Build-up
| Program | Mon | Tue | Wed | Thu | Fri | Sat | Sun |
|---|---|---|---|---|---|---|---|
| Stiffness relief (20 minutes) | ✓ | ✓ | ✓ | ✓ | |||
| Endurance strength (40 minutes) | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| Maximal strength (30 minutes) | ✓ | ✓ |
Weeks 4–12 – Main strengthening phase
| Program | Mon | Tue | Wed | Thu | Fri | Sat | Sun |
|---|---|---|---|---|---|---|---|
| Endurance strength (50-60 minutes) | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| Maximal strength (30-40 minutes) | ✓ | ✓ | ✓ |
Setting the intensity
- When you start the treatment program you will initially feel nothing. At that point no treatment is occurring.
- To make it work you must increase the current intensity.
- Everyone feels the current differently and reacts differently. You will even notice differences between days.
- This is why the device does not set a value for you automatically. You must find the appropriate value yourself.
- If you increase the intensity step by step you will feel fine twitches in your muscles.
- These contractions do not yet strengthen the muscle — you must increase the intensity further.
- The higher the intensity, the stronger the contraction you will experience, and the greater the effect.
- Above a certain (personal) value the treatment becomes painful. At that point reduce the intensity by a few mA.
- During treatment you should feel very definite contractions, but they must not be painful!
- Stimulate at the upper level of your comfort zone.
- If you do not provide sufficient intensity there will be no contractions and therefore no effect.
Finishing
- When the treatment time is over the program will finish.
- Turn off the device.
- Remove the electrode pads one by one carefully from your skin (do not pull by the cable) and place them back on the plastic protective sheet.
- Many people have reported that storing electrode pads in a regular refrigerator increases adhesive lifespan — I'll leave that choice up to you!
My recommendation – what to expect?
Gradual progression
Muscle strengthening does not happen in one day. You cannot expect meaningful change from a single treatment — at best you may get muscle soreness.
- Week 1: you must acclimatize your muscles to stimulation — lighter, less frequent treatments.
- Weeks 2–3: increasingly frequent and stronger treatments — "laying the foundations."
- End of week 3: the first noticeable results — your thigh muscles support you better and you feel better. But you are not "done" yet.
- After 2 months: gradually incorporate thigh-strengthening exercises into your daily routine.
- After 3 months: active exercise (physiotherapy) should be primary — I recommend using stimulation only as a supplement.
What happens if you stop?
If you do neither exercise nor stimulation, your muscle strength will decline back to the pre-treatment level within 2–3 weeks. Only regular activity can maintain gains — therefore it is important to learn thigh-strengthening exercises while using NMES.
Which device is suitable for knee stabilization?
Knee stabilization is training of innervated muscle (quadriceps, hamstrings). Classic EMS/NMES devices are required; you can choose from several suitable devices depending on the aim:
Sport-focused choice (Sport Pro line)
These devices have program libraries optimized specifically for lower-limb sport rehab and performance (Endurance strength, Maximal strength, Stiffness relief):
Triathlon Pro – multi-sport device
Multiple sport protocols, including full lower-limb muscle training and quadriceps protocols needed for knee stabilization.
Cycling Pro – for cyclists
Optimized for cyclists' needs with programs targeting lower-limb strengthening. Excellent choice for knee stabilization.
Runner Pro – for runners
Sport protocols designed for runners. Ideal for knee stabilization because running is a common source of knee injuries.
Soccer Pro – for football players
Protocols designed for footballers. Well suited to lower-limb and knee stabilization.
The Champion – multisport rehabilitation
Multisport rehab device for 13 sports. Suitable for knee stabilization and post-surgery rehab.
General multifunctional choice
Elite and Elite 150 – versatile for family use
Multifunctional, suitable for family use. Includes lower-limb sport and rehab protocols.
Premium 400 / Activa 700 – Globus mid-range
Versatile Globus devices with 4-channel build and appropriate program library.
Rehabilitation device family:
Genesy 1500 or Genesy 3000
Professional-level Genesy devices with lower-limb NMES protocols. Ideal for those seeking a versatile rehab tool in one device.
Muscle stimulation after surgery (TKA, ACL) →
Regaining lost muscle strength (EMS rehab) → Frequently asked questions
In clinical practice and experience, the first noticeable improvement appears towards the end of week 3 — your thigh feels firmer, resting knee pain may decrease, and mobility feels easier. Meaningful muscle strength increase and functional improvement are measurable after 6–8 weeks. After completing the full 12-week program quadriceps strength can improve substantially and this can be maintained provided that follow-up training continues.
Clinical trials indicate that 4–6 weeks of preoperative NMES training ("prehab") can significantly improve preoperative functional status (WOMAC, KOOS), which indirectly facilitates postoperative recovery.7 Consult your operating surgeon or physiotherapist — they will help set the appropriate protocol.
Clinical protocols generally recommend starting after the wound healing phase (about 10–14 days). Trials suggest that starting NMES as early as 3 weeks post-op can produce meaningful quadriceps strength gains.2 Always consult the orthopedic surgeon who performed the operation or the treating physiotherapist.
Clinical results are mixed. A 2024 RCT reported that NMES + exercise significantly improved muscle structure (VMO thickness) and functional indicators (WOMAC).4 However, a 2023 meta-analysis found that NMES + exercise is not significantly better for pain reduction than exercise alone.5 Realistic expectation: NMES improves muscle structure, which may indirectly reduce pain. Do not expect rapid, direct pain relief.
No. NMES complements, it does not replace active physiotherapy. Clinical trials show that NMES + active training produces significantly better results than either alone.4,8 NMES is especially valuable in the early postoperative weeks when pain and the surgical wound limit active training.
Yes — and this is common. If one knee is injured (after ACL surgery, unilateral osteoarthritis), priority should be strengthening the affected leg's quadriceps. NMES systems with 2 or 4 channels can be applied to both legs or only one. Tip: it is worth treating the opposite (healthy) leg 1–2 times weekly to avoid muscle asymmetry.
Before you start treatment — contraindications
NMES is generally safe, but it cannot be used in certain cases. Consult your treating physician or physiotherapist before starting treatment.
When NOT to use the muscle stimulator?
- Implanted pacemaker or defibrillator
- Suspected acute DVT (deep vein thrombosis) or newly diagnosed thrombosis
- Active purulent skin infection or open wound in the treatment area
- Malignant tumor in the treatment area
- Pregnancy (abdomen and lower back; for lower limbs consult your gynecologist)
- Epilepsy – only under medical supervision
- Fresh surgical wound in the treatment area – medical clearance required
- Severe cardiovascular disease, uncontrolled high blood pressure
- Severe sensory loss in the treatment area – increased caution (you may not feel overheating)
- Children under 18 years – only under medical supervision
Complementary treatment
Home NMES is a complement to knee rehabilitation, not a substitute for medical and physiotherapy care. A detailed contraindication list is available in the article on electrotherapy contraindications.
Summary – Quick overview
Sources
- Peng L, Wang K, Zeng Y, Wu Y, Si H, Shen B. (2021). Effect of Neuromuscular Electrical Stimulation After Total Knee Arthroplasty: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Frontiers in Medicine (Lausanne), 8, 779019. PubMed: 34926522
- Klika AK, Yakubek G, Piuzzi N, Calabrese G, Barsoum WK, Higuera CA. (2022). Neuromuscular Electrical Stimulation Use after Total Knee Arthroplasty Improves Early Return to Function: A Randomized Trial. Journal of Knee Surgery, 35(1), 104-111. PubMed: 32610358
- Labanca L, Rocchi JE, Giannini S, Faloni ER, Montanari G, Mariani PP, Macaluso A. (2022). Early Superimposed NMES Training is Effective to Improve Strength and Function Following ACL Reconstruction with Hamstring Graft regardless of Tendon Regeneration. Journal of Sports Science & Medicine, 21(1), 91-103. PubMed: 35250338
- Moezy A, Masoudi S, Nazari A, Abasi A. (2024). A controlled randomized trial with a 12-week follow-up investigating the effects of medium-frequency neuromuscular electrical stimulation on pain, VMO thickness, and functionality in patients with knee osteoarthritis. BMC Musculoskeletal Disorders, 25(1), 158. PubMed: 38378564
- Carvalho MTX, Guesser Pinheiro VH, Alberton CL. (2023). Effectiveness of neuromuscular electrical stimulation training combined with exercise on patient-reported outcomes measures in people with knee osteoarthritis: A systematic review and meta-analysis. Physiotherapy Research International, 29(1), e2062. PubMed: 37926438
- Talbot LA, Solomon Z, Webb L, Morrell C, Metter EJ. (2020). Electrical Stimulation Therapies for Active Duty Military with Patellofemoral Pain Syndrome: A Randomized Trial. Military Medicine, 185(7-8), e963-e971. PubMed: 32248227
- Savkin R, Buker N, Gungor HR. (2021). The effects of preoperative neuromuscular electrical stimulation on the postoperative quadriceps muscle strength and functional status in patients with fast-track total knee arthroplasty. Acta Orthopaedica Belgica, 87(4), 735-744. PubMed: 35172441
- Solie B, Carlson M, Doney C, Kiely M, LaPrade R. (2024). Oh, My Quad: A Clinical Commentary And Evidence-Based Framework for the Rehabilitation of Quadriceps Size and Strength after Anterior Cruciate Ligament Reconstruction. International Journal of Sports Physical Therapy, 19(12), 1600-1628. PubMed: 39628771
