A lumbar infiltration involves injecting a corticosteroid directly into the painful structures of the spine. The procedure lasts a few minutes, but the pain that follows the injection often raises more concern than the act itself. Understanding the mechanisms of this post-injection pain, its normal duration, and the signals that warrant medical advice allows for a less apprehensive recovery period.
Mechanism of post-injection pain: what happens in the spine
The pain felt after a lumbar infiltration does not mean that the procedure has failed. It results from a local mechanical and chemical process that the body takes a few days to resolve.
The needle passes through several layers of tissue (skin, paravertebral muscles, ligaments) to reach the epidural or peri-articular space. This path causes a micro-mechanical irritation of the tissues traversed. The volume of the injected substance also creates unusual local pressure, especially in a space already compressed by a herniated disc or a narrow lumbar canal.
The corticosteroid itself can generate a transient inflammatory reaction before producing its anti-inflammatory effect. This phenomenon, sometimes referred to as a “flare-up,” explains why the pain after lumbar infiltration may increase in the first hours before gradually decreasing.
Normal duration of pain after lumbar infiltration
The majority of patients experience discomfort or increased pain in the first hours following the procedure. This phase corresponds to both the dissipation of the local anesthetic (often associated with the corticosteroid) and the tissue reaction described above.
Post-injection pain generally lasts less than 48 hours. Beyond this timeframe, the anti-inflammatory effect of the corticosteroid gradually takes over. Maximum relief often occurs in the days that follow, sometimes lasting up to a week depending on the treated pathology.
Two variables significantly influence this duration:
- The type of infiltration performed: an epidural injection, which involves a deeper and more sensitive space, tends to cause more pronounced post-procedure pain than a posterior joint infiltration.
- The pre-existing inflammatory state: a spine that is already very irritated (acute sciatica, compressive hernia) reacts more strongly to the injected volume, prolonging the initial painful phase.
- The guidance used during the procedure: infiltrations performed under ultrasound or radiographic control allow for more precise targeting of the area to be treated, reducing unnecessary tissue trauma and potentially shortening the period of mechanical pain.
Warning signals: when post-injection pain requires medical advice
The distinction between normal pain and a complication relies on a few specific criteria. Pain that remains stable or decreases gradually after 48 hours falls within the expected range.
A fever that appears in the days following the infiltration is the most serious warning signal. It may indicate an infection at the injection site, a rare complication that requires prompt management. Increasing local redness, unusual swelling, or discharge at the puncture site also fall under the same urgency.
The emergence of new neurological symptoms (loss of strength in a leg, urinary issues, widespread numbness) in the hours following the procedure also justifies immediate contact with a physician. These signs, which are exceptional, may indicate nerve compression related to the injected volume or, more rarely, an epidural hematoma.
Pain persisting beyond a week
If the initial pain (the one for which the infiltration was prescribed) returns to its pre-procedure level after one to two weeks, this does not indicate a complication. It rather suggests that the infiltration did not produce the expected therapeutic effect on the underlying pathology. The physician will then reassess the strategy: a second infiltration may be considered, or other therapeutic options will be discussed.
Managing pain in the days following the procedure
Strict bed rest after a lumbar infiltration is no longer recommended. Current guidelines on low back pain, including after injectable procedures, favor resuming appropriate physical activity to reduce the risk of chronic pain.
Specifically, the first 24 hours warrant avoiding intense efforts (lifting heavy loads, engaging in sports activities). Walking is not only permitted but recommended. It maintains spinal mobility and limits reactive muscle stiffness.
Analgesics and medication options
Paracetamol is the first-line treatment for moderate post-injection pain. Local application of cold (ice pack wrapped in cloth) on the lumbar area can alleviate the local inflammatory component in the first hours.
For more pronounced pain, step II analgesics (tramadol, codeine) remain an option. As of December 1, 2024, the dispensing of these substances requires a more regulated specific prescription, which means planning this prescription with the physician prior to the procedure rather than seeking it urgently afterward.
Physiotherapy after lumbar infiltration
Resuming physiotherapy sessions after a lumbar infiltration is possible and often beneficial, but the recommended delay varies. Waiting a few days allows the corticosteroid to begin working and to treat a partially relieved spine, making mobilization exercises more effective and better tolerated.
The physiotherapist adapts the techniques: gentle passive mobilizations and light core stability work are prioritized initially, before progressing to more dynamic exercises.
Pain after a lumbar infiltration is part of a normal physiological response of the spine to the procedure. The 48-hour window remains the main reference point. Beyond that, it is the evolution of the initial pain that guides the subsequent treatment, in conjunction with the prescribing physician.