Medication Summary
In addition to resolving the etiology of the knee pain, the ED physician must make every effort to relieve suffering as completely and expeditiously as possible. Distinguish acute injury from chronic distress. Consider the intensity of the pain. The perception of pain is subjective, and therapy should be individualized.
Objective parameters, such as tachycardia, are unreliable. Minor trauma to the knee that involves the ligaments, muscles, and joints usually causes a mild to moderately severe, self-limiting discomfort. An enormous choice of analgesics is available for use by the ED physician, but pharmacologic agents tend to fall into 2 general categories: nonnarcotic and narcotic analgesics. Furthermore, consider the best route for delivering the drug.
Nonnarcotic analgesics
Class Summary
Patients with pain accompanying minor acute soft-tissue injuries of the knee generally benefit from a short course of nonnarcotic analgesics, with acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs) being the most frequently prescribed agents. If inflammation is a component of the injury and if no contraindication is present, prescribe NSAIDs, as acetaminophen lacks anti-inflammatory properties. An increasing number of NSAIDs are available for use. NSAIDs share a common mechanism of action, which involves inhibiting the production of pain-mediating prostaglandins. In general, NSAIDs provide a comparable degree of pain and inflammatory relief, but they differ in dosing schedules.
Choosing an NSAID to prescribe can be perplexing; data comparing these agents are meager, and individual responses are inconsistent. Because no individual NSAID is clearly superior, base decisions on personal experience, safety profiles, cost, and convenience.
Acetaminophen (Tylenol, Feverall, Aspirin Free Anacin)
Most commonly ingested pain reliever; marketed in combination with other drugs to provide analgesia. Advantages include availability, cost, and relatively good safety profile. Onset of relief usually in 20-30 min. Extended-release preparations do not appear to offer major benefits (other than dosing convenience) and may increase incidence of toxicity. For children, available as drops (80 mg/0.8 mL), elixir (160 mg/5 mL), tablets (80, 160, or 325 mg), and suppositories (125 or 325 mg).
Acetylsalicylic acid (Bayer Aspirin, Bufferin, Anacin, Ecotrin)
Prototype NSAID; used in combination with many other drugs; available OTC. Offers anti-inflammatory benefits, unlike acetaminophen. Effective in PO, suppository, and topical preparations. Therapeutic anti-inflammatory serum level 15-30 mg/dL.
Ketorolac (Toradol)
Choice of parenteral pain medications dispensed in ED. Frequently overlooked fact is that this medication is an NSAID, with all of the group's attendant risks and that it costs almost 20 times more than morphine (and 140 times more than ibuprofen). Data supporting superiority over other analgesics scarce.
Ibuprofen (Motrin, Advil, Nuprin)
Widely used NSAID, also available OTC, derivative of propionic class of NSAIDs and considered safest of NSAIDs. Available as tablets 200, 400, 600, and 800 mg; pediatric dosage forms available as tab and PO suspension (20 mg/mL). Advise taking with food or milk if possible; caution in children with flulike illnesses.
Narcotic analgesics
Class Summary
Patients reporting inadequate pain relief from NSAIDs may benefit from short-term supplementation with an opioid compound. A wide array of products is available. PO hydrocodone (Lortab, Lorcet, Vicodin, Anexsia), schedule III narcotic, and oxycodone (Roxicet, Percodan, Tylox), schedule II substance, usually provide additional pain relief. Codeine-containing products (schedule III) are not as reliable for alleviating pain. Although relative potencies of oxycodone and hydrocodone are approximately 0.33 of those with parenteral morphine, PO codeine is 0.05. Mixed agonist-antagonist PO agents (eg, butorphanol, nalbuphine, pentazocine), offer no real advantages to opioid agents yet increase incidence of adverse effects. Common adverse effects include constipation, nausea, respiratory depression, sedation, and urinary retention.
General approved dosage of hydrocodone is 5-10 mg combined with acetaminophen 500-750 mg administered PO q6h prn. Oxycodone analgesic preparations typically combine 2.5-5 mg of oxycodone with 325 mg of acetaminophen, dosed as 1-2 tabs PO q4h prn for moderate to severe pain. Acetaminophen with codeine (Tylenol #3) contains 30 mg of codeine with 325 mg of acetaminophen. Usually, 1-2 pills q4h prn is recommended.
Elixirs containing hydrocodone (Hycodan) are convenient for children older than 6 years with moderately severe to severe pain and who are unable to swallow pills. One teaspoon (5 mL) of Hycodan contains 5 mg of hydrocodone, with 1.25-2.5 mg administered q4h, depending on the child's size and severity of pain. The elixir of Tylenol with codeine for children contains 120 mg of acetaminophen and 12 mg/5 mL of codeine in an alcohol base (7%).
Orally administered drugs generally impart a slower onset of action. For patients in severe pain or for those patients who must be kept NPO, parenteral agents may be necessary. Although the IM route may be more convenient for the staff, the IV route offers a number of advantages. Narcotics administered IV provide a rapid and predictable onset of action and are easier to titrate. Morphine and meperidine are the most commonly used parenteral narcotic agents.
Hydrocodone and acetaminophen (Vicodin, Lorcet, Lortab, Anexsia)
Drug combination indicated for relief of moderately severe to severe pain.
Oxycodone and acetaminophen (Percocet, Tylox, Roxicet)
Drug combination indicated for relief of moderately severe to severe pain.
Acetaminophen and codeine (Tylenol #3)
Drug combination indicated for treatment of mild to moderately severe pain.
Morphine sulfate (Oramorph, MS Contin, Duramorph)
Criterion standard for relief of acute severe pain; may be administered in a number of ways; commonly titrated until desired effect obtained. IV morphine demonstrates half-life of 2-3 h; however, half-life may be 50% longer in the elderly.
Meperidine (Demerol)
Narcotic analgesic with multiple actions similar to morphine; however, may cause less constipation, smooth muscle spasm, and depression of cough reflex than similar analgesic doses of morphine. Serum half-life 2 h. Metabolism occurs by hepatic demethylation into normeperidine. Patients with moderately severe to severe liver disease may develop excessive levels of metabolites, precipitating CNS adverse effects, including tremors and seizures.
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Anatomy of the knee.
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Knee ballottement.
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Lachman test.
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Anterior drawer sign.
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Pivot test.
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McMurray test.
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Apley compression test.
