Osteoarthritis: A review of treatment options

Key Points

Abstract

Osteoarthritis (OA) is the most common form of arthritis and the leading cause of disability in the United States, especially among older adults. Treatment options have primarily focused on alleviating the pain often associated with this condition. Acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs) are often employed for relief of mild-to-moderate pain associated with OA. NSAIDs are typically more effective than acetaminophen; however, because of adverse effects associated with long-term use of NSAIDs, acetaminophen is considered first-line therapy. Safety concerns over traditional pharmacotherapeutic agents used in the management of OA, such as NSAIDs and opioids, have led healthcare professionals to seek other options. Trials of disease-modulating agents that focus on preventing further damage to the joints have the potential to change how this disease state is managed. This article reviews nonpharmacologic and pharmacologic approaches to management of OA of the knee and hip. (Formulary. 2009;44:143–151.)

The development of OA involves multiple factors that contribute to excessive joint loading, repetitive motion or injury, and inflammation. The most common risk factors in the etiology of OA include advanced age, obesity, past occupation, participation in certain sports, joint trauma, and family history.^1–3

Genetic factors are also thought to play a role in the development of OA, and different genes may be implicated in different types of arthritis.³ Heberden nodes, bony enlargements of the distal interphalangeal joints of the hand, are 10-fold more prevalent in women than in men, and they occur twice as often in women whose mothers developed these nodes. Genetic factors have been linked to generalized OA, as well as OA of the first metatarsophalangeal joint. This genetic link has been substantiated in twin studies, which have demonstrated a 60% correlation in hip OA and a 70% correlation in spine OA between twins.⁴

To date, many intracellular regulators have been identified as potential markers for the expression of OA pathologies. These identified markers include interleukin-1 (IL-1), interleukin-4 (IL-4), and genes that code for asporin, an extracellular matrix protein, and calmodulin, an intracellular regulator.⁵

PATHOPHYSIOLOGY

OA has previously been considered a disease resulting from wear and tear of the joints; however, it can be more accurately described as a condition that is a result of various biochemical, biomechanical, inflammatory, and immunologic factors.⁵ These factors can cause structural and functional failure of synovial joints with erosion and loss of articular cartilage, meniscal degeneration, and osteophytes.⁶ OA can be categorized into 2 major etiologic classes: primary (idiopathic) or secondary. Primary OA is the most common type and can be further classified as localized (involving only 1 or 2 sites) or generalized (affecting ≥3 sites).^3,5 Secondary OA is associated with a known cause such as rheumatoid or other arthritis, trauma, metabolic or endocrine disorders, or congenital factors.

Signs and symptoms of OA may be present for months or years before medical attention is sought; deep, aching, generalized pain is typically what causes patients to initially seek medical attention. Pain is most commonly associated with movement in the beginning stages of disease but also occurs at rest in advanced OA. Other symptoms include joint stiffness that is most pronounced in the morning or after a period of inactivity ("gelling"), lasts <30 minutes, and remits with movement; crepitus; limited or reduced range of motion; and joint deformity in late stages.

NONPHARMACOLOGIC TREATMENT OPTIONS

The goal of OA treatment is to control symptoms, prevent disease progression, minimize disability, and improve quality of life. Management of OA includes varied techniques and principles, both nonpharmacologic and pharmacologic in nature.

Prevention of OA is the best treatment option. Limiting modifiable risk factors such as obesity, smoking, joint damage, and lack of adequate exercise can have a significant effect on decreasing the risk of OA development. Joint damage can be avoided by limiting exposure to vocational and recreational activities that involve prolonged high-impact and repetitive motion, kneeling, squatting, or heavy lifting. Repetitive recreational activities such as running have not demonstrated the same association with increased development of OA.⁴ Once a patient has been diagnosed with OA, appropriate nonpharmacologic methods should be employed as first-line treatments in mild disease or concurrently with pharmacologic management in progressive disease. These techniques include patient education, weight loss, exercise, physical and occupational therapy, assistive devices, acupuncture, ultrasound, and surgery.

Education. Patient education should always be the first step and a continued, integral part of OA treatment. Education should address the disease process, prognosis, and appropriate treatment options, as well as proper resources that the patient can consult for accurate self-management information and programs. The Arthritis Foundation offers such patient-oriented support.⁷

Diet and exercise. Obesity remains the most important and modifiable risk factor for the development of OA. In a study of 2,623 patients, Niu et al⁸ observed a significant relative risk for developing knee OA in obese (2.4) and very obese (3.2) patients versus those patients with normal body mass index (BMI) (P<.001). The results, however, did not demonstrate an overall correlation between obesity and the progression of existing OA. A 4-year cohort trial conducted by Wang et al⁹ in 39,023 volunteers determined that there was a 3- to 4-fold increased risk of primary joint replacement associated with increased body weight, BMI, fat mass, and percentage fat. Increased waist circumference and waist-to-hip ratio were also associated with an increased risk, suggesting that both biomechanical and metabolic mechanisms associated with adiposity contribute to the risk of joint replacement.⁹ Therefore, weight reduction and exercise in combination should be encouraged in all patients with OA, especially in those with OA of the knee and hip. Although each alone is beneficial in disease treatment and prognosis, one 18-month program of a combined regimen of caloric restriction and exercise resulted in a 24% improvement in physical function and a 30.3% reduction in knee pain, a significant improvement compared with the participants who followed only diet restrictions or exercise alone.¹⁰

Physical and occupational therapy. Formal physical and occupational therapy is useful in those patients who are not benefiting from home exercise programs or in those who need further instruction in range of motion, joint protection, or muscle-strengthening principles. In a randomized, controlled trial of 83 patients, Deyle et al¹¹ determined that improvements in walking distance, function, pain, and stiffness in the group receiving manual therapy of the knee (n=42) were clinically and statistically superior (P<.05) to the improvements in a control group receiving subtherapeutic ultrasound therapy after 8 weeks and 1 year of treatment. At 1 year, 20% of the control group versus 5% of the treatment group had undergone arthroplasty. Recommendations for exercise regimens should be patient-specific and should include both strengthening and low-impact aerobic exercise such as walking, swimming, or bicycling. Strength training that focuses on the quadriceps, adductor, and abductor muscles has been demonstrated to improve both knee and hip stabilization. All exercise regimens should be initiated by a trained exercise practitioner and continued at home, with intensity and duration increasing slowly as tolerated.^12,13

Assistive devices. Patients with OA may consider using canes and orthotics to assist with stability. The American College of Rheumatology (ACR) recommends using a cane contralaterally to the affected knee joint to manage OA symptoms.^14,15 Reaction forces in an osteoarthritic hip may be reduced by 50% when a patient uses a cane in the contralateral hand. A randomized, controlled trial assessed the use of orthotics and demonstrated no short-term symptomatic relief within a 6-week period, whereas 2 additional randomized, controlled trials determined that knee braces and therapeutic taping of the knee were effective interventions for the management of OA.^16–18 A 6-month, prospective, parallel-group, randomized clinical trial in 119 patients concluded that the use of knee braces (neoprene sleeves and unloader braces) in the management of OA of the knee results in a significant improvement in quality of life (P=.001) and function (P≤.001) specific to OA.¹⁷ Unloader braces appear more effective than neoprene sleeves in relieving symptoms.¹⁷ A 3-week trial of therapeutic knee taping demonstrated a significant reduction in knee pain (21 of 29 patients) when compared with both a control-tape group (14/29) and a no-tape group (3/29); this reduction in pain was maintained for 3 weeks after treatment cessation.¹⁸

Alternative. Acupuncture may provide some pain relief when administered alone or in combination with diclofenac.¹⁹ Acupuncture alone has been associated with improved function; however, it cannot be determined to what extent this improvement is caused by a placebo effect.²⁰ In randomized, placebo-controlled studies, therapeutic ultrasound has not been demonstrated to be more effective than placebo after 3 months, whether continuous therapeutic ultrasound, galvanic current, or shortwave diathermy was used.²¹

PHARMACOLOGIC TREATMENT OPTIONS

Pharmacologic treatment options are listed in the table on p 146-47.^24,25

Acetaminophen and NSAIDs. Acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs) are effective for mild-to-moderate pain associated with OA.²⁶ Data suggest that NSAIDs are more effective than acetaminophen; however, based on the side- effect profile of NSAIDs, acetaminophen is preferred as first-line therapy.

A systematic review involving 5,986 patients confirmed that acetaminophen is effective for the treatment of OA.²⁶ This study demonstrated that the number needed to treat (NNT) ranges from 4 (for pain response) to 16 (for overall pain reduction). Acetaminophen was more effective than placebo in 5 of 7 trials; the meta-analysis of these data confirmed that acetaminophen is significantly more effective than placebo for reduction of overall pain and pain on motion. This systematic review also confirmed that NSAIDs were superior to acetaminophen for OA in 10 trials. Acetaminophen should be avoided in patients with hepatic impairment.

NSAIDs have consistently demonstrated efficacy for pain relief in OA; however, a meta-analysis of 23 trials that included 10,845 patients demonstrated that NSAIDs are only slightly more effective than placebo for short-term pain relief in OA of the knee.^27–29 All NSAIDs, including cyclooxygenase-2 (COX-2) selective agents, are equally effective for pain relief in OA; choice of agent should be based on patient comorbidities, cost, and side-effect profile.^29,30 Gastrointestinal (GI) and cardiovascular (CV) risks limit routine use of NSAIDs in many patients (see table); a large meta-analysis recommended limiting use of NSAIDs because of the potential for serious adverse effects.²⁹ Caution is recommended when NSAIDs are administered to patients with CV risk factors; COX-2 selective agents are known to cause CV events, but nonselective agents (such as diclofenac and indomethacin) have also been implicated in increasing the risk of CV complications.³¹ Nonacetylated salicylates may be considered for patients with mild renal insufficiency.

COX-2 selective NSAIDs may be beneficial in patients at high risk for peptic ulcer disease or GI bleeding; however, the GI protective benefits of COX-2 selective agents may be negated if the patient is also taking aspirin (even in low doses).³² Patients who do not respond to selective COX-2 NSAIDs, are on concomitant aspirin therapy, or are at increased CV risk may be candidates for treatment with a nonselective NSAID plus a proton-pump inhibitor (PPI) or misoprostol for added GI protection.^33,34 Misoprostol protects against gastric and duodenal NSAID-induced ulcers. Misoprostol is contraindicated in pregnant woman because of its abortive effects and should be used with caution in women in their child-bearing years who are not using an effective contraceptive. Misoprostol is available alone or in combination with diclofenac. Adverse effects such as abdominal cramps and diarrhea may limit its use.³⁴ Prophylaxis therapy with a PPI in combination with an NSAID has been demonstrated to be superior to histamine (H₂) receptor antagonists combined with an NSAID in preventing GI ulcers and erosions, although the combination of PPI and NSAID is not FDA approved.³³ The decision of which therapy a patient is prescribed should take into consideration the cost, compliance issues, and past response to other therapies.

Topical analgesics. Topical NSAIDs and capsaicin may offer alternatives for patients unable to tolerate systemic agents and may also offer adjunctive therapy for those exhibiting partial response to conventional therapy. The long-term efficacy of topical NSAIDs has been debated; however, a meta-analysis of 4 trials that examined the efficacy of topical NSAIDs in trials lasting >4 weeks demonstrated that diclofenac and eltenac are effective for long-term pain relief in knee OA.^35,36 Topical capsaicin works by depleting the neuropeptide substance P and must be used for at least 3 to 4 weeks to achieve maximal benefit; a meta-analysis of 3 trials confirmed that topical capsaicin is more effective than placebo for pain relief in OA.³⁷ Capsaicin is commonly associated with a transient local burning sensation. Despite this effect, 1 study reported dropout rates as low as 2%.³⁸ Given its unique mechanism of action, topical capsaicin may also be useful as an adjunct to an oral analgesic.

Although not formally indicated for OA, lidocaine 5% patches may also offer a topical alternative for some patients.³⁹ One trial suggests that these patches may be as effective as COX-2 selective NSAIDs; however, these data are limited as the trial ended early because of safety concerns with COX-2 agents.⁴⁰

Glucosamine and chondroitin. The efficacy of glucosamine and chondroitin remains controversial. Glucosamine, which is naturally produced in the body, is an aminomonosaccharide that acts as a substrate for glycosaminoglycans, proteoglycans, and hyaluronic acid to form articular cartilage. Chondroitin also serves as a building block for joint cartilage.⁴¹ The large-scale Glucosamine/Chondroitin Arthritis Intervention Trial (GAIT; N=1,583) failed to demonstrate a significant reduction in overall pain after 24 weeks in patients treated with glucosamine only, chondroitin only, or the combination of glucosamine plus chondroitin; however, a subgroup of patients with moderate-to-severe pain did experience significant pain reduction with the combination of glucosamine and chondroitin.⁴² An ancillary study of GAIT lasting 2 years evaluated joint space width in 572 patients; the combination of glucosamine and chondroitin failed to demonstrate a reduction in joint width loss.⁴³ A systematic review of 20 studies involving 2,570 patients demonstrated conflicting results based on glucosamine formulation.⁴⁴ Another meta-analysis of 15 trials concluded that there is likely evidence of some degree of efficacy for these agents.⁴⁵ Based on the benign side-effect profile of both agents and their potential for efficacy, a trial of glucosamine and chondroitin might be warranted in patients with mild-to-moderate knee OA.

Narcotic analgesics. According to the American Academy of Rheumatology, opioid analgesics such as codeine and oxycodone are not considered a first-line treatment option and should be considered only if traditional methods of pain management (eg, acetaminophen, NSAIDs, or tramadol) have been ineffective for OA or are intolerable; even then, only low-dose opioids should be used, especially in elderly patients.^46,47 The use of strong opioids for long-term pain relief in patients without cancer is a controversial topic; the risks of dependence, addiction, and hyperalgesia are the primary concerns.^46,47 Investigators conducted a meta-analysis of 18 placebo-controlled trials in 4,856 patients treated with weak or strong opioids.⁴⁸ Opioids significantly reduced the intensity of pain but had only moderate effects on physical function. Efficacy was assessed by measuring changes in pain intensity or an increase in physical function. The pooled effect size of all opioids for pain intensity was –0.79 (95% CI, –0.98 to –0.59). The pooled effect size of all opioids for physical function was –0.31 (95% CI, –0.39 to –0.24). Safety was measured by the number of treatments that had to be discontinued because of adverse effects. The most common adverse effects were nausea, constipation, dizziness, somnolence, and vomiting. The average rate of discontinuance was higher among patients treated with strong opioids (31%) than among those treated with weak opioids (19%). The number needed to harm among patients treated with strong or weak opioids versus those treated with placebo was 4 and 9, respectively. The high incidence of adverse effects should be considered before opioids are used as a treatment option in patients with OA.

The fentanyl patch provides continuous medication for 24 hours, but this agent should not be used in opioid-naïve patients. According to Langford et al,⁴⁹ patients with hip or knee OA experienced a reduction in pain and improved functionality with the fentanyl patch compared with placebo during a 6-week trial.⁴⁹ Although adverse effects with this agent are similar to those observed with other opioids, with fewer reports of constipation, the patch is thought to be more tolerable. For optimal results, opioids should be used in conjunction with nonpharmacologic therapies and considered for short-term use only.

Tramadol. Tramadol is an atypical opioid with a dual mechanism of action; it acts centrally on the mu-opioid receptors and inhibits the reuptake of norepinephrine and serotonin.⁵⁰ Unlike NSAIDs, tramadol has not been associated with GI bleeds. Eleven trials have compared tramadol or tramadol/acetaminophen with placebo or active controls for the treatment of OA.⁵¹ Patients taking tramadol or tramadol/acetaminophen experienced less pain and increased functionality but reported twice as many adverse effects (see table). The effectiveness of tramadol is still questionable; lack of anti-inflammatory properties and the development of tolerance to tramadol may limit this agent's effectiveness.⁵¹ Tramadol is contraindicated in patients with opioid hypersensitivity and in patients with acute alcohol intoxication.

Intra-articular glucocorticoids. For patients experiencing an acute local inflammation with a buildup of fluid in the joint (effusions), intra-articular glucocorticoid injections (triamcinolone acetonide, triamcinolone hexacetonide, betamethasone, and microcrystalline methylprednisolone) are a safe and effective nonsurgical option.^52,53 The efficacy of corticosteroid injections in areas other than the knee is questionable. Studies evaluating the efficacy of corticosteroid injections in OA of the hip have not been conducted, and the procedure is technically difficult to perform, as it requires fluoroscopic guidance.⁵⁴ The ACR recommends that, to reduce the risk of infection, these injections be performed by an experienced physician. A cell count, Gram stain, and culture should be performed if infection is suspected; leukocytosis, fever, or rapid onset of an effusion may be indicative of an infection in the joint.⁵² The dose of injection depends on the size of the joint being treated; these agents create a rapid response to pain, but long-term pain relief has not been established.⁵⁵

Hyaluronate injections. Intra-articular hyaluron (hyaluronic acid) is a polysaccharide found in the extracellular connective tissue that can act as a joint lubricant. When compared with placebo and NSAIDs, hyaluronic acid injections provided only a slight benefit in pain relief.⁵⁶ These agents are approved only for OA of the knee, not of the hip. Although the onset of action is slower than that observed with corticosteroids, these injections have the benefit of a longer duration, but they are also more costly.⁵⁵ Hyaluronate injections are administered as weekly injections for 3 to 5 weeks; hylan G-F 20 is administered as a single injection.

Disease-modulating agents. Disease-modulating agents are being investigated as alternative agents for OA. These agents are not intended for the treatment of painful symptoms but for the prevention of further damage to the joints or for the slowing of disease progression in joints already affected. Tetracyclines have certain anti-inflammatory properties and are inhibitors of collagenase and gelatinase; in OA, collagenase, gelatinase, and stromelysin levels are increased.⁵⁷ Doxycycline may slow the progression of OA. A 30-month trial comparing doxycycline 100 mg twice daily with placebo in 431 obese women demonstrated radiologic evidence of slowed progression of joint space narrowing (by 33%) in doxycycline-treated patients versus placebo-treated patients.⁵⁸ Withdrawals were more frequent in the doxycycline group because of adverse effects such as nausea, heartburn, and photosensitivity (23 vs 9).

Diacerein is currently not available in the United States. This agent has anti-inflammatory and analgesic properties when 50 mg is administered orally twice daily. Studies have demonstrated that diacerein is modestly effective compared with placebo and as effective as NSAIDs for pain relief of hip or knee OA.⁵⁹ The most common adverse effect is diarrhea, which is typically observed during the first 2 weeks of treatment.⁶⁰

FUTURE DIRECTIONS

Progress is being made in identifying and understanding the possible genetic contributions to the development of OA. This identification of the common alleles responsible for coding regulatory proteins involved in cartilage function may lead to the potential for new drugs that affect these regulatory proteins and thus potentially prevent, treat, or eradicate OA. The investigation into the role of inflammatory markers in OA such as IL-1, prostaglandin E2, tumor necrosis factor (TNF)-alpha, and nitric oxide also may lead to further treatment options for disease eradication.⁵

CONCLUSIONS/ RECOMMENDATIONS

Dr Seed is assistant professor, Pharmacy Practice, Massachusetts College of Pharmacy and Health Science, Worcester. Dr Dunican is assistant professor, Pharmacy Practice, Massachusetts College of Pharmacy and Health Science. Dr Lynch is associate professor, Pharmacy Practice, Massachusetts College of Pharmacy and Health Science.

Disclosure Information: The authors report no financial disclosures as related to products discussed in this article.

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