A cortisone shot, also known as a corticosteroid injection, is a common medical treatment used to manage localized pain. This medicine delivers a potent anti-inflammatory agent directly into a specific area, such as the knee joint. This targeted approach is generally effective when inflammation is the primary driver of pain and swelling. When an injection fails to provide relief, it suggests the underlying issue is not responding to inflammation suppression, or other factors are limiting the drug’s effectiveness.
How Cortisone Shots Work in the Knee
Cortisone is a synthetic version of cortisol, a hormone naturally produced by the adrenal glands. When injected into the knee, this drug suppresses the local immune response and reduces inflammation. It achieves this by inhibiting the production of inflammatory molecules, such as prostaglandins and cytokines, which cause pain and swelling in the joint.
The injection often includes a local anesthetic, providing immediate but temporary numbness. The corticosteroid’s anti-inflammatory effect is not instantaneous and typically begins to work gradually over a few days to a week. The primary goal is to provide weeks or months of pain relief, allowing time for physical rehabilitation and strengthening. Cortisone does not heal the underlying damage, and its effects are temporary as the drug is metabolized and absorbed by the body.
Factors That Reduce Treatment Effectiveness
A lack of relief may be due to technical issues with the injection, even if the diagnosis is accurate. Effectiveness relies on precise placement, ensuring the medication reaches the exact source of inflammation within the joint. If the needle misses the target area, the drug cannot exert its localized anti-inflammatory action, leading to treatment failure. This is more likely when the injection is performed without imaging guidance, such as ultrasound or fluoroscopy.
The extent of joint damage also limits the drug’s success. If the knee has advanced osteoarthritis, the mechanical breakdown of cartilage and bone may be too severe for the anti-inflammatory effect to overcome the structural source of pain. In these cases, the pain is caused by bone-on-bone friction, which a corticosteroid cannot correct.
Some biological factors can also cause the treatment to fail. A small percentage of individuals are non-responders, meaning their inflammatory pathways do not react to the drug as expected. Additionally, some patients may rapidly absorb or metabolize the corticosteroid, causing the drug concentration at the pain site to diminish quickly. This rapid clearance results in a much shorter period of relief than the expected duration.
Underlying Conditions Not Responsive to Cortisone
The injection often fails because inflammation is not the primary cause of the pain, indicating a diagnostic problem. Cortisone is effective only against inflammation, not against mechanical or structural failures in the joint. For example, a torn meniscus or damaged ligaments are structural issues that result in mechanical pain, not pain driven by inflammation.
Injecting cortisone into a knee with a meniscal tear or torn tendon will not repair the damaged tissue or stabilize the joint. Continued mechanical irritation from movement will perpetuate the pain, overriding the temporary anti-inflammatory effects. The underlying issue is a breakdown of structural integrity, requiring a mechanical solution rather than a chemical one.
Pain may also originate from a source outside the knee joint, known as referred pain. Nerve entrapment or irritation in the lower back, called radiculopathy, can cause pain felt strongly in the knee. In this scenario, the pain signals come from the nerve root in the spine, not the knee joint itself. A cortisone shot into the knee will have no effect on the irritated nerve in the lumbar spine, explaining the lack of relief.
Next Steps After Injection Failure
If a cortisone shot does not provide meaningful relief, the first step is to return to the physician for a thorough re-evaluation. This visit confirms the initial diagnosis and may involve new imaging studies, such as an MRI scan, to assess soft tissue damage more closely. The injection’s failure often acts as a diagnostic tool, pointing toward a non-inflammatory or structural source of the pain.
Alternative non-surgical treatments can then be explored based on the updated assessment. Physical therapy is often recommended to address underlying muscle imbalances or biomechanical issues stressing the joint. Other injection options include viscosupplementation, which involves injecting hyaluronic acid for lubrication and shock absorption in arthritic joints.
The physician may also discuss regenerative therapies, such as platelet-rich plasma (PRP) injections, which use the patient’s concentrated growth factors to promote healing. For patients with severe structural damage unresponsive to conservative measures, a surgical consultation may be warranted. This can involve procedures ranging from arthroscopic repair of tears to total knee replacement for end-stage joint degeneration.