A cortisone shot offers quick pain relief for joint and tendon problems. How we manage you afterwards depends on what was injected and how active you were beforehand. So do you need to rest after a cortisone injection, and when can you return to weight training and running?

What are the side effects of a cortisone injection?

Cortisone shots are very safe when used for the right reasons. As with any treatment, though, there are potential side effects:

  • Allergic reaction (rare)
  • Infection (around 1 in 10,000)
  • Skin thinning and discolouration — reduced by using a skin-sparing cortisone, and by using ultrasound to place the injection accurately
  • Bleeding into the joint
  • A temporary rise in blood sugar in people with diabetes, lasting about two weeks
  • A cortisone flare, causing pain for 3–5 days (see below)

Some people worry about longer-term effects, such as tendon weakening or joint damage. Recent studies suggest repeated cortisone injections can affect cartilage, and cortisone can weaken a tendon for a few weeks. We reduce these concerns by using cortisone sparingly, for the right reasons, and with ultrasound guidance to place it accurately. For more information about side effects, see this guide on side effects of cortisone injection. 

What happens straight after a cortisone injection?

Once you’ve had the shot, offload the injected area for the rest of the day. A knee or foot injection means reducing your step count; a shoulder injection means avoiding lifting or reaching with that arm.

Key aftercare for the first day:

  • Keep the area clean. Leave the bandage on until the end of the day, then wash the area.
  • Don’t submerge it. Showering is fine, but avoid hot tubs and swimming pools for 24 hours.
  • Manage any flare. Apply ice for 10–15 minutes every 2–3 hours, and take ibuprofen 400mg three times daily until it settles.
  • Avoid heavy activity — walking, running, or cycling — after hip, knee, or foot injections.

What should you do for a cortisone flare?

Pain after a cortisone injection is usually due to a cortisone flare. A flare typically starts about 6 hours after the injection and lasts up to 5 days.

We think it happens because cortisone forms tiny crystals, which irritate the soft tissue and cause inflammation. If you develop a flare, do the following:

  • Rest from activity — including the gym and running — until it settles.
  • Regular ice packs (10 minutes every 3–4 hours)
  • Ibuprofen 400 mg three times daily helps (or other NSAIDs such as Naproxen, diclofenac or etoricoxib). 

How long do you need to rest after a cortisone injection?

As a rule, rest the injected area for two days, then gradually build your activity back up. If a flare is still present after two days, keep resting until it settles.

The return to full activity depends on what was injected. Tendon injections need longer — one to two weeks — with the longest rest for weight-bearing tendons such as the Achilles, patellar, gluteus medius, and peroneal tendons.

Returning to weight training

men weight training after a cortisone injection

When you go back to the gym depends on the structure injected and the exercises involved. As a general guide, return to the gym 3–4 days after the injection, starting with body parts away from the injected area. After seven days, gradually load the injected structure, staying protective of it for around ten days.

Example: after a shoulder tendon injection

  • Days 1–2: rest the shoulder; treat any flare with ice every 4 hours and ibuprofen
  • Day 3: return to the gym for lower-body exercises and lower-limb aerobic work
  • Day 7: reintroduce lighter back and pulling exercises; avoid pushing (shoulder and chest)
  • Day 10: reintroduce lighter shoulder and chest work at 50% of your previous load, and re-engage with physiotherapy
  • Then: build weight and intensity of pushing exercises under a physiotherapist’s guidance

Returning to running

For upper-limb injections, you can return to running after two days, or once the flare settles.

For lower-limb injections, rest from running for seven days — though the exact time depends on the structure. In general, return after seven days for a joint injection, and after ten days for a tendon injection.

Example: after a hip joint injection for hip arthritis

  • Days 1–2: rest the hip; treat any flare with ice every 4 hours and ibuprofen; reduce step count by 50%
  • Day 3: upper-body weights and swimming without kicking
  • Day 7: cross-training, including cycling and lower-body weights
  • Day 10: re-engage with physiotherapy
  • Days 14–21: graded return to running under a physiotherapist’s guidance

For a runner-focused guide — including cortisone flare and marathon timing — see running after cortisone injections.

Frequently asked questions about return to exercise after cortisone injection. 

Can I walk after a cortisone injection in my knee?

Avoid walking for exercise immediately after a lower-limb injection, and reduce your step count for a few days — especially if you develop a flare. Using public transport, a car, or a taxi for 3–4 days after a knee injection helps. A little everyday walking is fine if there’s no flare, but keep it light.

Can I drive home after a cortisone injection?

Best not to drive yourself immediately. Insurers often require you to be able to perform an emergency stop, and cortisone can briefly cause dizziness or affect your vision. Arrange a lift, taxi, or public transport, and resume driving the day after — provided any flare isn’t severe.

How long after a cortisone shot can I drink alcohol?

Alcohol increases blood flow and can promote bleeding, so avoid heavy drinking for 24 hours after the injection.

Can I take painkillers after a cortisone injection?

Yes. If you have pain afterwards, paracetamol and ibuprofen are both fine, and ibuprofen also helps settle a flare.

Why shouldn’t I use heat after a cortisone injection?

Heat increases blood flow to the area, which can worsen swelling and pain. Use ice rather than heat — 10–15 minutes every 3–4 hours — for pain and swelling in the first few days.

How long should I rest for a tendon injection versus a joint injection?

Joint injections generally take about a week to take effect. Tendon injections need longer — up to 10 days to 2 weeks — with the most caution for large weight-bearing tendons such as the Achilles and patellar tendons, because cortisone temporarily weakens tendon tissue.

Does a post-injection infection present differently from a cortisone flare? 

Yes. Infection after a cortisone injection is rare, with an estimated risk of 1/10,000, making it much less common than a flare. Generally, an infection presents 3-4 days after an injection, with increasing pain, swelling, and general symptoms such as fever and chills. However, in the early phase of infection, the presentation may resemble a cortisone flare. Nonetheless, an infection will always get worse while a flare settles over a day or two.  

Final word from Sport Doctor London about return to exercise after cortisone 

As a general rule, rest the injected area for at least 2 days, and expect to return to the gym or running between 7 and 14 days, depending on what was injected and why. The single most important reason to rest is to protect a temporarily weakened tendon and to avoid provoking a flare.

Dr Masci is an expert in ultrasound-guided injections for joints and tendons. If you’d like to discuss an injection, contact the team here or call +44 (0) 203 488 0350.

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