Why No Swimming After a Cortisone Shot?

Doctors advise against swimming after a cortisone shot primarily because the injection creates a tiny puncture wound that has not yet sealed, and submerging it in pool, lake, or ocean water introduces bacteria directly into a joint or tissue that is temporarily immunosuppressed by the steroid. The risk of a serious joint infection is low in absolute terms, but the consequences can be severe enough that most providers tell patients to stay out of the water for at least 24 to 48 hours. Beyond infection, there are biomechanical and pharmacological reasons to give the injected area a brief rest before returning to a repetitive activity like swimming.

The Puncture Site Needs Time to Close

A cortisone injection uses a needle that is considerably larger than, say, the fine-gauge needles used in a flu shot. The needle passes through skin, subcutaneous tissue, and often into a joint capsule or tendon sheath. That tract does not seal the instant the needle is withdrawn. Research on skin puncture channels shows that evidence of microchannel repair and resealing becomes apparent at roughly 8 to 24 hours after a needle puncture.¹ During that window, the path from the skin surface down to the injection site is essentially an open corridor. Pool water, hot tub water, and natural bodies of water all harbor bacteria and other microorganisms. Submerging an unsealed puncture wound in contaminated water is the textbook setup for introducing pathogens into tissue that would normally be well-protected by intact skin.

This is the same logic behind the standard advice not to soak in a bath, hot tub, or lake after any joint injection. It is not unique to cortisone, but cortisone adds a second layer of concern that makes the caution more urgent.

Cortisone Temporarily Suppresses Local Immune Defenses

Corticosteroids work by dialing down inflammation, which is exactly why they relieve pain in an arthritic knee or a swollen shoulder. But the immune system and the inflammatory response overlap heavily. When you inject a potent steroid into a joint, the drug dampens the local immune cells that would normally detect and kill invading bacteria. Evidence from a narrative review of peripheral corticosteroid injections found that immune cells involved in both innate and adaptive responses are suppressed for about 48 hours after injection, and key signaling molecules that coordinate the immune response remain suppressed for over 96 hours.² This means the tissue around the injection site is less capable of fighting off bacteria for two to four days after the shot.

So you have two problems stacking on top of each other: a physical opening that has not closed, and a local immune environment that is temporarily less effective at dealing with intruders. Swimming in water containing bacteria during that window is a gamble that most clinicians consider unnecessary.

How Real Is the Infection Risk?

The absolute risk of developing a joint infection, known as septic arthritis, after a cortisone injection is quite low even without swimming. A large multicenter review covering over a million cortisone injections found the incidence of confirmed septic arthritis to be about 1 per 15,275 injections.³ A separate retrospective cohort study looking at large-joint injections found a risk of roughly 10 cases per 10,000 individuals within 21 days.⁴ These numbers sound reassuringly small, and they are. But septic arthritis is not a mild complication. It can destroy cartilage quickly, require emergency surgery to wash out the joint, and in severe cases lead to permanent damage or even systemic sepsis. The low probability is counterbalanced by the high severity.

An analysis of 278 cases in which complications occurred after corticosteroid injections found that in roughly 40% of cases, errors in technique or aftercare contributed to the problem, including failures to maintain aseptic conditions and insufficient time between injections.⁵ The takeaway is that many infections after cortisone shots are at least partly preventable. Avoiding unnecessary exposure to bacteria-laden water in the first couple of days is one of the simplest precautions a patient can take.

Swimming Puts Mechanical Stress on the Injected Area

Infection risk is the headline reason to skip the pool, but there is a separate biomechanical argument that matters especially if your cortisone shot was in the shoulder, elbow, hip, or knee. Swimming is a repetitive, load-bearing activity, and the forces involved are higher than many people realize. Competitive swimmers perform around 30,000 shoulder rotations per week, and even recreational swimmers put considerable repetitive stress through their upper-body joints with each stroke cycle.⁶ Shoulder pain is the most common musculoskeletal complaint among swimmers for exactly this reason.

After a cortisone injection, the goal is usually to let the steroid settle into the target tissue and reduce inflammation before the area is loaded again. Jumping straight into a swimming workout works against that goal. A clinical recommendation for high-level athletes receiving intra-articular cortisone suggests one to two days of rest for the affected joint, followed by a gradual increase in activity. The rationale is to maximize the injection’s local anti-inflammatory benefit and reduce how much of the drug gets absorbed into the bloodstream where it does not help.⁷ If professional athletes, who have access to top-tier medical support, are advised to rest for at least a day or two, a recreational swimmer should feel comfortable doing the same.

This is especially relevant for shoulder injections. If you received a cortisone shot for shoulder bursitis, rotator cuff tendinitis, or impingement syndrome, freestyle or butterfly strokes are among the worst movements to perform while the joint is still settling down. The combination of overhead rotation, internal rotation under load, and rapid repetition is a lot to ask of a shoulder that was inflamed enough to need an injection in the first place.

How Long Should You Actually Wait?

There is no single universally standardized waiting period, which is partly why patients get confused. Different providers give different timelines, and the advice can range from “keep the bandage on for a few hours” to “no pool for a week.” Here is what the evidence supports:

First 24 hours: The puncture site is still closing. Avoid submerging the area in any body of water, including pools, hot tubs, baths, lakes, and the ocean. A shower that rinses over the site is generally considered fine because the water flows off rather than soaking the wound.
24 to 48 hours: The skin barrier should be largely restored. The local immune suppression is still significant during this window. Most orthopedic and sports-medicine providers recommend resting the injected joint during this period anyway.
48 to 96 hours: Immune signaling molecules remain somewhat suppressed, but the puncture site is sealed and the worst of the vulnerability has passed. Many providers clear patients for gentle aquatic activity at this point, particularly if the injection site shows no signs of redness, swelling, or increased pain.

The one-to-two-day rest recommendation for athletes returning to sport aligns well with the skin-closure and immune-suppression timelines.⁷ For swimming specifically, where you are both submerging the site and loading the joint, 48 hours is a reasonable minimum. If your injection was in the shoulder and you are a regular lap swimmer, waiting a full week before returning to your normal training volume is not overcautious.

Pool Water Versus Open Water Versus Hot Tubs

Patients sometimes assume that a chlorinated pool is safe because the chlorine kills germs. Chlorine does reduce bacterial counts, but it does not sterilize pool water. Public pools contain bacteria from other swimmers’ skin, and the chemical balance fluctuates depending on how recently the pool was treated, how many people are using it, and the water temperature. Warm-water therapy pools and hot tubs are a particular concern. Warmer water encourages bacterial growth, and hot tubs are notorious for harboring Pseudomonas and other opportunistic organisms even when properly maintained.

Open water adds another layer of risk. Lakes, rivers, and ocean water contain a far broader range of microorganisms than a well-maintained pool. Saltwater does not disinfect a wound. If you received a cortisone shot and you are on vacation near the beach, the advice is the same: stay out of the water for at least a couple of days.

Your own bathtub falls somewhere in between. While tap water is cleaner than pool or natural water, soaking an unsealed puncture site in standing bath water for an extended time still gives bacteria an opportunity to enter. Most providers suggest sticking to showers for the first 24 hours after any joint injection.

What About Aquatic Therapy After a Cortisone Shot?

Here is where things get more nuanced. While swimming as exercise is discouraged in the days immediately after a cortisone shot, aquatic therapy performed under supervision and at the right time can actually be beneficial for recovery. A clinical study comparing conventional shoulder exercises to hydrotherapy in patients who had received intra-articular injections found that the hydrotherapy group experienced significantly better pain relief by the end of the first week, along with faster improvement in shoulder function.⁸ The study concluded that hydrotherapy during early management of shoulder problems after injection was safe and provided better functional outcomes than land-based exercises alone.

The key distinction is timing and setting. Supervised aquatic therapy typically begins a few days after the injection, uses warm water in a controlled clinical environment, and involves gentle range-of-motion exercises rather than vigorous lap swimming. The water provides buoyancy that unloads the joint while allowing movement, which is a very different kind of stress than cranking out freestyle intervals. If your provider suggests pool-based physical therapy after a cortisone shot, that is not contradicting the swimming restriction. The two activities are quite different in terms of joint loading, water quality control, and supervision.

What You Can Do While Waiting

Resting the injected joint does not mean total immobility. In fact, being completely sedentary can lead to stiffness, especially in joints like the shoulder and knee. The recommendation is to rest the specific joint or region that was injected while progressively increasing activity over a couple of days.⁷

If you had a knee injection, gentle walking on flat ground is usually fine after the first day. Stationary cycling with low resistance can keep the joint moving without heavy impact. If the shot was in your shoulder, you can do gentle pendulum exercises, walk, use a stationary bike, or do lower-body workouts. The goal is to avoid loading the injected joint through its full range of motion under resistance for the first day or two while remaining active enough to prevent stiffness elsewhere.

For dedicated swimmers who are itching to get back in the water, using a kickboard (for a shoulder injection) or pull buoy (for a lower-body injection) can let you swim with reduced loading on the affected joint once you are past the 48-hour window. Just be honest with yourself about whether “easy kicking” is going to stay easy or escalate into a full workout once you smell the chlorine.

Signs That Something Has Gone Wrong

Most cortisone injections are uneventful. A cortisone flare, where the joint feels worse for a day or two before the steroid kicks in, is common and not a sign of infection. But certain symptoms after any injection warrant a call to your doctor, and they warrant an urgent call if you went swimming or submerged the injection site in water:

Increasing redness and warmth: Some redness right after the injection is normal. Redness that spreads or gets worse after 48 hours is not.
Swelling that gets worse: Mild swelling can follow the injection, but progressive swelling, especially with heat, suggests something else is happening.
Fever: A systemic fever after a local injection is a red flag for infection.
Severe pain that begins days after the shot: A cortisone flare typically peaks in the first 24 to 48 hours and then improves. Pain that starts or worsens several days later is different and should be evaluated.

Septic arthritis develops quickly once bacteria establish themselves in a joint, and early treatment with antibiotics and sometimes surgical irrigation makes a significant difference in outcomes. If you did swim earlier than recommended and then develop any of the symptoms above, mention the swimming to your doctor. It changes the diagnostic calculus.

When the Advice Varies by Injection Site

Not all cortisone shots are created equal in terms of post-injection precautions. An injection into a large joint like the knee or shoulder deposits the steroid into a fluid-filled capsule, and the consequences of introducing bacteria into that space are more serious than with a superficial soft-tissue injection. Septic arthritis in a large joint can cause rapid cartilage destruction within days. Softer-tissue injections, like those into a plantar fascia or a tennis elbow tendon, still carry infection risk, but the downstream consequences tend to be more manageable.

The swimming advice is most conservative for large-joint injections (shoulder, knee, hip, ankle) and slightly less restrictive for superficial soft-tissue injections, though the infection-pathway logic applies to both. If you had a cortisone shot into your shoulder specifically for swimming-related shoulder pain, the irony is not lost on anyone, but the joint that is causing you trouble is exactly the one that needs the most rest before you return to the activity that aggravated it.

Spinal injections, including epidural steroid injections, have their own aftercare protocols that are typically more restrictive and specific. Those are a separate category, and your provider will give you tailored instructions that go well beyond “no swimming.”

The Corticosteroid’s Effect on Nearby Tissue

Beyond infection and immune suppression, there is a tissue-level reason to go easy on the injected area. Corticosteroids, while excellent at reducing inflammation, can also have effects on cartilage and tendon tissue. Rest following injections has been recommended in part to minimize potential harmful effects on cartilage and to reduce systemic absorption of the drug.⁷ Vigorous activity immediately after injection can increase blood flow to the area, which speeds up how quickly the steroid is flushed out of the local tissue and into the bloodstream. That means less of the drug stays where you need it, and more of it circulates systemically where it provides no local benefit but can cause side effects like blood sugar elevation or sleep disruption.

Swimming, especially vigorous lap swimming, is the kind of full-body cardiovascular exercise that significantly increases blood flow. Doing it within hours of a cortisone shot could dilute the local effect you are hoping for. Even from a purely pragmatic standpoint, you paid for the injection (or your insurance did), and you want it to work. Giving it a couple of quiet days to do its job is not just about avoiding complications. It is about getting the most out of the treatment.