If you are not using cortisone injections as a part of your treatment strategy for common orthopedic conditions, I strongly urge you to start. Corticosteroid injections are a safe and effective treatment option for many orthopedic diagnoses. They are inexpensive, easy to administer, and often provide quick and long-lasting relief of the pain associated with arthritis, tendonitis, bursitis, and many other conditions. These injections are extremely useful tools that any practitioner caring for ailments of the musculoskeletal system ought to know and use.

Frequency

It is generally accepted that cortisone injections should be used judiciously. The specifics on this are somewhat vague. Some claim that the maximum frequency of injections for any one joint is one a month, not to exceed three per year. Others interpret the rule to be no more than one cortisone injection in any given joint every 4 months. The medical evidence supporting these guidelines remains elusive, but it is generally accepted that, given too frequently, cortisone can weaken connective tissue, including articular cartilage, tendons, and ligaments. What is even less clear is how many injections total a person can have (in any particular joint) in their lifetime. Some feel that patients should be limited to three injections (lifetime total) in any one joint. Others feel there is no lifetime limit, provided the rule of “one every 4 months” is not broken. Until a consensus can be reached, or until adequate medical evidence is put forth, it is certainly reasonable to inject any given joint with a maximum frequency of one injection every 4 months for a maximum duration of 3 years.

Sterile Technique

Proper sterile technique is important. The inside of a joint or tendon sheath is similar to an abscess cavity. It is a dead space with relatively poor circulation. Infections grow easily in such spaces, and cortisone is known to have a weakening effect on the immune system, so there is a higher risk of creating an infection with an intra-articular corticosteroid injection than, say, an intramuscular injection such as an immunization. That said, the risk of infection from in-office cortisone injections is surprisingly low, on the order of 1 in 15,000. The practitioner need not wear sterile gloves, although a pair of unsterile gloves is recommended because there is a risk that the practitioner will come in contact with the patient’s body fluids.

Prep an area of skin at the proposed injection site with betadine or chlorhexidine, then lay an alcohol square over the site where you plan to inject. The alcohol square is important because you can press on it with your fingertip and confirm that you are in the right spot without actually touching the sterile patch of skin where the needle will enter. When you are ready to inject, slide the alcohol square out of the way and proceed to pass the needle through the skin. Be sure not to touch and contaminate the needle as it passes into the target tissue.

Systemic Effects

Very little of the injected corticosteroid is absorbed systemically, but, certainly, some very small amount is. Diabetics may report a transient (1- to 2-day) increase in blood sugar levels, and a few patients will experience facial flushing, increased heart rate, and dysphoria. These reactions are usually fairly mild and can be treated with an antihistamine such as Benadryl. Rarely, patients will report intense burning or aching pain at the injection site. This reaction, called a “steroid flare,” is typically short lived (1-2 days) but can be severe enough to warrant the temporary use of narcotic pain relievers.

Patients on Anticoagulation Therapy

All of the injection techniques reviewed here except the technique for administering a lumbar epidural steroid injection are safe to use on patients receiving systemic anticoagulation therapy. Remember that patients on warfarin therapy, for instance, routinely have their international normalized ratio (INR) measured by venipuncture. If they don’t have bleeding complications from having a needle stuck directly and purposefully into a major vein, they are unlikely to have bleeding complications from one of these injections.

Equipment and Materials

All injections should be prepared by someone who understands and practices good sterile technique. Handling the syringes, needles, and vials of medication has to be done with caution to avoid contamination. To prepare the skin, you will need a chemical skin prep (e.g., betadine or chlorhexidine), nonsterile gloves, and an alcohol square (see previous discussion). The injection will be a combination of corticosteroid and lidocaine drawn up into the same syringe, so that the patient can receive both medications with only one needle puncture. The preferred ratios of lidocaine and corticosteroid will vary from joint to joint and from practitioner to practitioner, but a typical large-joint (knee, shoulder, hip) injection would contain 1 mL (40 mg) of steroid and 4 mL of lidocaine. A typical medium-size joint (wrist, elbow, ankle, heel) injection would contain 1 mL of corticosteroid and 1 mL of lidocaine, and a small-joint injection (interphalangeal joints of toes or fingers) might typically contain ½ mL (20 mg) of corticosteroid and ½ mL of lidocaine. Most orthopedic offices prefer lidocaine without epinephrine. Although it is controversial, there is some evidence that epinephrine is a strong enough vasoconstrictor that it can cause ischemic damage when injected into small body parts like fingers and toes. Because many orthopedic offices treat hands and feet, lidocaine with epinephrine is not used to avoid inadvertently administering it into one of these areas.

The most commonly used corticosteroids are Kenalog and Depo-Medrol; both are equally effective. The desired concentration is 40 mg/mL. Be sure to choose a corticosteroid that is in suspension, not in solution. The difference is apparent on visual inspection of the medication in the glass vial in which it is packaged. Corticosteroids that are in solution are as clear as water. Those in suspension separate out into a watery liquid and a chalky, white powder that settles to the bottom of the vial until shaken, after which the medication appears milky white. The clear, watery-appearing preparations where the corticosteroid is in an aqueous solution should not be used for these injections. These medications are intended for situations where systemic administration is desired. For orthopedic injections, our goal is local, not systemic, treatment. Corticosteroid preparations that are in suspension are less apt to leave the joint or tendon sheath into which they are injected, although even with these preparations, a trace amount of the steroid can reach the systemic circulation. This is evidenced by the observation that diabetics who receive these injections will occasionally experience a transient increase in serum glucose levels (see previous discussion).

The best syringe to use is one with a Luer-Lock tip. Needles screw into the tip of the Luer-Lock syringe, making it harder for them to accidentally come off the tip of the syringe. If the syringe loaded with the injection to be used is stored vertically, with the needle end down (e.g., in the breast pocket of your white jacket), the chalky white powder can settle down into the hub of the needle and clog it. Even after vigorous shaking, the needle hub can be blocked enough that, when the plunger on the syringe is depressed, the needle pops off and the cortisone and lidocaine spray all over everything. This is always embarrassing (and it is universally agreed that such topical applications are far less effective!).

Needle choice is also important. A 1½-inch, 22-gauge needle will work well for almost every type of injection. The 1½ inches of needle length will get you into the knees and shoulders of all but the heaviest patients. An 18-gauge needle would be the ideal bore from the standpoint of the injector. One of the ways we determine that the needle is in the joint is to feel for the loss of resistance that occurs when the needle is in a free space like the inside of a joint or the subacromial space of the shoulder. Imagine your goal was to advance a needle through the wall of your cheek and into the inside of your mouth. If you are not deep enough, and the tip of the needle is still in the thick, dense tissue that makes up the wall of your cheek, you would encounter a lot of resistance as you attempt to push the plunger on the syringe. If the needle has successfully entered the empty space that is the inside of your mouth, then there is little resistance, and the plunger can be depressed easily. The presence or absence of resistance is important feedback that helps us know if our needle is where we want it to be, and those changes in resistance are easier to detect with a large-bore needle.

Our patients would prefer we use a 27-gauge needle. It hurts less. A 22-gauge needle is a good compromise. Its caliber is big enough that we can feel changes in resistance, but it is small enough in diameter not to hurt very much.

Anesthetizing the Skin

Some practitioners will inject 1-2 mL of lidocaine or other local anesthetic with a small-gauge needle into the surface of the skin to anesthetize the area through which the needle will pass during the injection. This is certainly a reasonable thing to do. Another way to anesthetize the skin is to spray it with ethyl chloride. Ethyl chloride is liquid that evaporates quickly at room temperature, cooling the skin and making it less sensitive. It only works for a second or two after it is applied, so you have to work quickly. Once you have mastered an injection technique, you may find that it is easier for you and the patient to proceed without anesthetizing the skin. Most orthopedic injections are not particularly painful and can be done safely and effectively without this additional step.

Results

Patients may experience immediate results during the lidocaine phase of the injection, but the anti-inflammatory effect of the corticosteroid can take several days to occur. Exactly when patients feel relief varies quite a bit from patient to patient. For practical reasons, I advise my patients that it can take up to 10 days to get the full effect (it takes my office 10 days to transcribe my office note and get it in the chart, so if they call me after 10 days to complain that they didn’t get relief from the injection, I’ll have my note for reference when we discuss alternative treatment options).

Final Tip

If you’re going to try skiing for the first time ever, don’t go down a double black diamond, advanced, “experts-only” run. When trying any of these techniques for the first time, pick a thin, cooperative patient who will remain relaxed and tolerates needles well. If you are new to giving these injections, start with the easy ones like the hip greater trochanteric bursa or the lateral epicondyle of the elbow. For each of the injection techniques described in the following material, I have listed a “degree-of-difficulty” rating from 1 to 10, with 1 being the easiest and 10 being the hardest. I recommend starting with the simple ones and introducing the more difficult ones after you have built up your confidence and skill. Also, realize that many of the techniques described here involve touching bone with the tip of the needle. Fear not! This does not injure the patient.

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  1 mL (40 mg) corticosteroid (Kenalog or Depo-Medrol); 4 mL lidocaine; 22-gauge, 1½-inch needle

  
  
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  Patient position: supine on exam table

  
  
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  Degree of difficulty: 3

There are many different ways to successfully deliver an injection into the knee joint. The technique described here uses a superior-lateral approach. It is safe, easy, and effective. The patient is positioned supine with their knees relaxed and extended (Figure 9-1). One advantage of this technique is that it is difficult for a patient in this position to watch the procedure. For some patients, watching the procedure can make them nervous and upset, and that makes it more difficult for them to relax. Also, in the rare case of a vasovagal event, the patient is safer in the supine position than in other positions, such as the seated position used for some knee injection techniques. You may need to rotate the patient’s leg so that the patella is truly anterior because most patients will lie in slight external rotation when relaxed (Figure 9-2).

Prior to prepping the skin, the knee is palpated, and the proposed site is chosen. Try to feel the medial, lateral, superior, and inferior edges of the patella. If you are planning to inject with your right hand, place the index finger of your left hand on the medial edge of the patella and use the left hand to push the patella laterally. Our entry point is just posterior to the lateral edge of the superior half of the patella (Figure 9-3). Pushing the patella laterally makes it easier to identify the lateral edge of the patella, which is where the injection will be given. It is easier to get into the joint from the lateral side because the lateral quadriceps muscle doesn’t come down as far (distally) as the medial quadriceps muscle does (Figure 9-4). On the lateral side of the patella, there is much less tissue between the surface of the skin and the inside of the knee joint, making it easier to get in from this direction.

It is helpful to imagine that the patella is a hockey puck resting on the top of a log. In this injection technique, our goal is to slide the needle under the puck. If we have positioned the patient properly, with the patella centered anteriorly, the flat undersurface of the patella is parallel to the ground, and our needle should be oriented parallel to the ground as well. If you look at a lateral view of the knee (Figure 9-5), you can see that the undersurface of the patella is not as flat as a hockey puck, it is shaped more like a rocker bottom that curves from superior to inferior. The patella is closest to the femur at its center point (black arrows in Figure 9-5), and because the space between the patella and femur is so tight there, that is a difficult place to try to enter the joint. The patella and femur diverge away from each other as you go above or below this center point, creating a bigger space for the needle. The space below the center point is occupied by the retropatellar fat pad, so it is best to aim for the space above (superior to) the center point (the space marked with a target in Figure 9-5).

So, as you are preparing to give the injection and you are feeling the knee to better understand the location of the patella, identify the “equator” (the centerline that divides the patella into superior and inferior halves) of the patella and pick a point along the lateral edge of the patella that is about 2 centimeters above this centerline. The needle should enter the skin at this point, staying parallel to the ground and directed straight across toward the medial side as you advance into the joint (Figure 9-6).

Although we often refer to the different “compartments” of the knee joint (the medial compartment, the lateral compartment, the patella-femoral compartment), there are no true separate compartments. The inside of the knee is like the inside of your mouth. It is one big, open space, and anything injected into one compartment quickly flows into all of the other compartments. Technically, in the knee injection technique described here, the needle is entering the patella-femoral compartment, but because this compartment freely communicates with all of the rest of the knee joint, an injection given here delivers medication equally to the entire knee joint space.

It is important that the needle be advanced deep enough to pass completely through the skin and subcutaneous tissue and then through the joint capsule to slide under the patella. Continuing the analogy between the knee and the mouth, to push a needle through your cheek and into the open space within your mouth, you have to make sure the needle makes it all the way through the “wall” of your cheek and into the open space inside your mouth. I recommend advancing the needle a full inch. If our desired target is a point deep to the upper third of the center of the patella, we will need to advance the needle at least an inch to get there (Figure 9-7). If you think your needle is in the proper place, but when you start to inject, there is a lot of resistance as you depress the plunger on the syringe, you may still be in the “cheek” of the knee, and you should advance the needle in deeper. If the needle is in the right spot, there should be little resistance as you inject. Remember to keep the index finger of your other hand pushing on the medial side of the patella. If you insert the needle and feel it contact bone, resist the temptation to pull the needle back. Leave the needle touching the bone and give the patella a couple quick shoves with your index finger. If the needle moves, your needle is on the patella and you need to try again with a more posterior entry point. If the needle doesn’t move, then the bone you are on is the femur and you need to try again using a more anterior entry point.

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  1 mL (40 mg) corticosteroid (Kenalog or Depo-Medrol); 1 mL lidocaine; 22-gauge, 1½-inch needle

  
  
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  Patient position: supine on exam table

  
  
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  Degree of difficulty: 1

The pes anserine (Latin for “goose foot”) tendons are the tendons of the semitendinosus, sartorius, and gracilis muscles. They attach to the medial tibia a few centimeters inferior to the medial joint line of the knee in a pattern that resembles the three toes of the foot of a goose (Figure 9-8). If a patient has tenderness to palpation here, they may have a pes anserine tendonitis or bursitis. A cortisone injection can be a quick-and-easy remedy for this condition. Prep the skin over the point of maximal tenderness, then advance the needle until you feel it contact the surface of the tibia bone. The injection site is 3-4 centimeters distal to the medial joint line on the flat, subcutaneous surface of the tibia (Figure 9-9). Inject directly onto the surface of the tibia.

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  1 mL (40 mg) corticosteroid (Kenalog or Depo-Medrol); 4 mL lidocaine; 22-gauge, 1½-inch needle

  
  
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  Patient position: seated, arms at side

  
  
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  Degree of difficulty: 6

The shoulder subacromial space injection is second only to the knee joint injection in terms of its importance and utility. Subacromial impingement is by far the most common condition you will see in adults with shoulder pain, and the subacromial injection plays a major role in nonoperative treatment of this frequently encountered diagnosis. The subacromial space can be injected from either a lateral or posterior approach. I favor the lateral approach, but the posterior approach also works well.

For the lateral approach, the patient is positioned sitting, with their arm at their side (Figure 9-10). Positioned in this way, the weight of the arm helps pull the humerus down to open up the space. Start by identifying the posterior-lateral corner of the acromion (Figure 9-11). The scapular spine, a prominent bony ridge along the posterior aspect of the scapula, terminates as a bony process called the acromion. The scapular spine and the acromion look a little bit like the shaft and the blade of a hockey stick (Figure 9-12). The scapular spine and the posterior-lateral corner of the acromion are easy to palpate on even the heaviest patients.

To inject using a lateral approach, start at the posterior-lateral corner and move anteriorly, pressing hard with your finger to feel the lateral edge of the acromion all the way to its tip (Figure 9-13). The lateral edge of the acromion is not as easy to palpate in obese or muscular patients. Pick a point about three-quarters of the way from the posterolateral corner to anterior tip of the lateral edge of the acromion (the white dot in Figure 9-13). The needle should enter 1-2 centimeters inferior to this point (at the X in Figure 9-14). Be sure your needle is not aiming parallel to the ground or aiming down. It should be aiming up at about a 45-degree angle (Figure 9-15). If you aim down or parallel to the ground, you may inadvertently inject the rotator cuff muscle or tendon rather than the subacromial space.