While there are a variety of treatment options for osteoarthritis, this author offers a thorough review of the literature on continuous heat therapy for patients with osteoarthritis (OA). Accordingly, she emphasizes the appropriate use of this modality as a first-line therapy for OA pain.

Osteoarthritis (OA) is the most common form of arthritis and the leading cause of disability in the United States. Treatment goals for OA include alleviation of pain and stiffness, improving or maintaining joint function, and maintaining one’s quality of life. There is a wide variety of treatment modalities for this condition.1,2 These modalities range from conservative treatments (self-management, physical therapy) to pharmacologic therapies (NSAIDs, intraarticular injections) and alternative medicines such as glucosamine and chondroitin (see “A Review Of Pertinent Treatment Options For OA” on page 23).



While there is no known cure for OA, heat therapy is the most common and popular conservative intervention for achieving pain relief and function integrity.

Indeed, heat therapy has been a mainstay of conservative treatment for OA for decades and is often a patient-controlled intervention. In order to achieve the therapeutic heat transfer effects of increased tissue metabolism, deep tissue temperature, blood flow and muscle lengthening, researchers have emphasized reaching an intramuscular temperature of at least 40ºC (104ºF). In order to achieve this, a minimum of 3 to 4°C (37.4 to 39.2°F) increase in surface temperature is required.3

The usual sources of heat therapy include warm compresses, ultrasound treatments, warm baths/showers, heating pads, and topical gels and plasters. While these therapies may achieve therapeutic heat transfer parameters, most of these methods offer very short-term benefits as the actual application usually only lasts for 15 to 30 minutes. Additionally, heating pads carry the risk of tissue injury secondary to burns.
In recent years, a new approach to heat therapy has arrived in the form of continuous low-level heat wraps (CLLHWs). Over-the-counter brand names include ThermaCare, Well Patch and Cura-Heat. These self-regulating, air-activated wraps provide up to eight hours of continuous, low-level heat (approximately 104 0F/40 0C).

A Review Of Pertinent Treatment Options For OA

- While osteoarthritis (OA) is more common in the elderly, it can occur at any age, primarily as a consequence of trauma, chronic inflammatory arthritis or congenital malformation. Also referred to as degenerative joint disease, OA is caused by deterioration of articular cartilage with subsequent formation of reactive new bone at the articular surface. Since some patients may have significant discomfort that may be too much to address with heat therapy alone, one may need to consider both conservative and pharmacologic treatment options. Pharmacologic therapies include non-narcotic analgesics, non-steroidal antiinflammatory drugs (NSAIDs); topical analgesics (such as capsaicin and aspirin creams and NSAID creams formulated by compounding pharmacists); narcotic analgesics; and intraarticular injections of corticosteroids and hyaluronic acid-like products. Hyaluronic acid-like products, also known as viscosupplementation agents, restore lubrication in the joint by adding supplemental hyaluronic acid, a key component of normal synovial fluid.17,18 However, clinicians should be aware that pharmacologic treatment often requires a combination of interventions and may cause potentially harmful side effects. Popular alternative medicines include glucosamine, which patients may take by itself or in combination with chondroitin. Although limited, current research indicates that glucosamine and/or chondroitin act as building blocks of proteoglycan molecules necessary for the regeneration of intraarticular cartilage.19 Both substances are extracts of animal products and are considered safe options for treating OA as they have minimal untoward effects. While the evidence is sparse, it does suggest that these substances offer moderate relief for OA pain.20,21 Non-pharmacologic treatments include: patient education and self-management programs; massage and physical therapy to maintain range of motion and strengthen regional musculature; osteopathic manipulation therapy; warm water exercise; and the application of cold or heat therapy. Individuals with postural and movement dysfunction often require support with durable medical equipment including canes, walkers, raised toilets, chair lifts, railings and joint protective devices. One study examined self-management methods for OA and rheumatoid arthritis (RA) in order to determine which methods patients consider most effective for treating pain and functional disability.22 The most common methods used were exercise, joint protection, assistive devices and heat application. Participants reported exercise, assistive devices and heat application as the most effective methods for self-management of OA and RA. Clinicians may consider referrals for surgical intervention for individuals with pain and restriction of movement that do not respond to usual treatment measures or when symptoms are so severe as to limit activities of daily living. In these individuals, one should initiate a referral to an orthopedic surgeon in order to evaluate the need for arthroscopic joint debridement, osteotomies or joint replacement.23

Generally, the wraps are made up of oval heat discs that contain iron, carbon, sodium chloride, sodium thiosulfate and water. When the CLLHW touches the air, it undergoes an exothermic oxidative reaction that produces heat. Research shows that heat disrupts the body’s usual pain cycle by stimulating an individual’s heat sensors (nocioceptors) to help block the pain sensation (nocioception) from reaching the brain and by relaxing deep muscles to reduce pain and tenderness.4 Recent research also reveals that CLLHWs provide significantly greater pain relief than gel and plaster-type topical heat applications.5,6

Other studies show the efficacy of CLLHWs in providing sustained increases in deep tissue temperature and blood flow. Using magnetic resonance thermography to assess changes in temperature distribution in lower back muscles, Mulkern and colleagues found that applying CLLHWs to the lower back muscles increased deep tissue temperature 2 to 5°C (35.6 to 41°F) at depths of 3.7 cm. (1.45 in.) below the surface of the skin.7

Studies show that continuous low-level heat wraps (CLLHWs), such as the ThermaCare heat wrap shown, provide sustained increases in deep tissue temperature and blood flow.

In a related study, researchers examined the effect of skin heating on trapezius muscle vascularity, measuring vascularity changes with a Doppler ultrasound (30 minutes post-heating).8 Their report states that topical heat significantly increases blood flow.

Similarly, Evans and Draper calculated temperature changes in the medial gastrocnemius muscle during a three-hour period of CLLHW application. Using an implantable thermocouple placed deep into muscle, the researchers found a significant increase in deep muscle temperature from the baseline to 30 minutes. According to the study, the temperature remained elevated at the three-hour interval.9

What The Research Reveals On The Clinical Efficacy
Of CLLHWs

Numerous investigations evaluate the clinical effectiveness of heat therapy with CLLHWs. One randomized, placebo-controlled study looked at the efficacy of CLLHWs in 93 adults with wrist pain due to sprains, tendonitis, carpal tunnel syndrome and OA.10 The study participants were randomized to the following treatments: heat wrap versus oral placebo or oral acetaminophen versus unheated wrap. The authors of the study collected data over a five-day period, which included three days of treatment and two days of follow-up.

The results showed that CLLHWs provide significant pain relief during days three through five and greatly increased grip strength on day three in participants with sprains, tendonitis and OA. For participants with carpal tunnel syndrome, CLLHWs gave study patients better pain relief, reduced joint stiffness, improved grip strength, a reduced perception of pain and disability, decreased symptom severity and increased functional status over the three-day treatment period. Additionally, CLLHWs provided significant benefits for two days following treatment.10

Neck pain due to osteoarthritis and other musculoskeletal causes responds well to heat therapy. Researchers found that individuals who utilized CLLHWs for eight hours for trapezius muscle pain had a significant reduction in pain, muscle tension and disability.

Another study compared the efficacy of eight hour CLLHWs, ibuprofen (1200 mg/day) and acetaminophen (4000 mg/day) in the treatment of acute, nonspecific low back pain in 332 ambulatory patients.11 Researchers recorded the data over two consecutive days of treatment and an additional two days of follow-up. The results showed that CLLHWs provided significantly superior pain relief on the first day of treatment and better sustained pain relief on follow-up days three and four.

In a similar study, the authors evaluated the effectiveness of eight hours of CLLHW therapy for the treatment of acute, nonspecific low back pain in a prospective, randomized, single-blind, placebo-controlled, multicenter clinical trial.12 The study focused on 219 participants with acute, non-specific low back pain. Subjects were randomized to one of the following groups: heat wrap versus oral placebo or oral ibuprofen versus unheated wrap. The study authors administered the treatments for three consecutive days with two days of follow-up.

The results showed that CLLHW therapy provides significant therapeutic benefits over the placebo during both the treatment and follow-up periods. The benefits included greater pain relief, less muscle stiffness and increased flexibility. The researchers also observed significant reductions in disability.12

In a related investigation, researchers evaluated the perceived value of CLLHW therapy among manual workers who had diagnosed low back pain due to manual handling, lifting, bending, twisting, awkward postures and whole body vibration.13 The results showed that CLLHW therapy significantly decreased both perceived pain intensity and the impact of pain on activities of daily living.

Other Important Findings In The Literature

Similarly, another study looked into the efficacy and cost benefit of CLLHWs in treating uncomplicated, acute low back pain.14 In a phase III trial involving 371 patients between the ages of 18 and 55, the authors compared three therapies: paracetamol, ibuprofen and CLLHWs. According to the study, 57 percent of patients using heat wrap therapy reported pain relief whereas 26 percent of patients had pain relief with paracetamol and 18 percent had pain relief with ibuprofen.

Economic evaluation of the three treatments indicated a modest treatment cost reduction with CLLHWs compared to the other treatment modalities.14 However, keep in mind that researchers collected this data from individuals participating in the United Kingdom National Health Service. Prices may vary in the U.S.
In another study, researchers evaluated 110 men and women with osteoarthritis of the knee who used CLLHWs for eight hours.15 Participants were given acetaminophen, ibuprofen or an oral placebo, and wore either a wrap with no heat or a ThermaCare heat wrap. The results of the study, which was recently presented at the Annual Meeting of the American Pain Society, revealed that patients using the CLLHW had significantly less pain and disability compared to the other treatment options.

Neck pain due to osteoarthritis and other musculoskeletal causes responds well to heat therapy. Researchers found that individuals who utilized CLLHWs for eight hours for trapezius muscle pain had a significant reduction in pain, muscle tension and disability compared to those who were treated with a placebo.16

In contrast to ibuprofen alone, heat therapy was associated with significantly reduced muscle tension and less pain. Study participants treated with CLLHW and ibuprofen, in comparison to participants who used placebo wraps and ibuprofen, reported significantly greater pain relief and decreased muscle tension. The study authors also found that continuous heat therapy was associated with significantly decreased disability in comparison to placebo wraps and study participants experienced sustained pain relief for several days after discontinuing use of the CLLHW.16

Treatment goals for osteoarthritis include alleviation of pain and stiffness, improving or maintaining joint function, and maintaining one’s quality of life.

A Few Comments About Contraindications And Side Effects

Although CLLHWs are safe to use for most patients, clinicians should exercise caution as they can produce redness, irritation and burns in some sensitive individuals. In most individuals, they are safe to wear overnight.

In order to reduce the risk of injury or untoward effects, CLLHWs should not be:

• used for more than eight hours in one 24-hour period or more than seven consecutive days in a row;
• heated or re-heated in a microwave or hot water;
• cut as it may produce a sudden burst of heat.

Clinicians should not utilize CLLHWs on infants, children or immobile individuals. They are also contraindicated for patients who have significant neuropathies or skin pathology. Clinicians should be very cautious about initiating CLLHW therapy in individuals with diabetes, vascular disease, rheumatoid arthritis, frail skin or dermatologic conditions.

Final Notes

Despite the fact that there is no known cure for OA, comprehensive treatment plans can decrease pain, improve mobility and minimize disability. In addition to obtaining a comprehensive history and performing a physical examination of the patient, the astute health care provider should conduct a thorough pain assessment and functional assessment that includes activities of daily living. Patient education should focus on self-management, including support services within their local communities or through the Arthritis Foundation (www.arthritis.com).

Clearly, the positive effects of heat therapy have been well documented in the literature. While the phenomenon of two or more days of extended pain relief following discontinuation of CLLHWs is not well understood, it does provide an additional positive benefit for the use of continuous low-level heat.
In light of the effectiveness, portability, ease in use, cost benefit and patient-controlled application of CCLHWs, clinicians should consider this modality as a first-line therapy for individuals with OA pain and decreased mobility.