Oral Painkillers, Steroid Shots Disappoint for Knee, Back Pain

April 20, 2015
Norman Bauman

Two new analyses throw cold water on the usefulness of acetaminophen for osteoarthritis or back pain, and of steroid shots for knee osteoarthritis.

Mallen C, Hay E. Editorial: Managing back pain and osteoarthritis without paracetamol.BMJ. 2015; 350:h1352. doi: 10.1136/bmj.h1352. March 31, 2015.

Henriksen M, Christensen R, Klokker L, et al.Evaluation of the Benefit of Corticosteroid Injection Before Exercise Therapy in Patients With Osteoarthritis of the Knee: A Randomized Clinical Trial. JAMA Intern Med. 2015; doi:10.1001/jamainternmed.2015.0461. Online March 30, 2015.

Acetaminophen (paracetamol) gets poor marks in a meta-analysis, showing no effect on low back pain and mixed results in osteoarthritis (OA).
 
And according to a separate study, an intra-articular corticosteroid injection before exercise therapy in patients with OA of the knee is of little value.

In the Australian study, the benefit of acetaminophen for reducing low-back pain intensity is an insignificant -0.5 points (CI -2.9 to 1.9.) on a scale of 0 (pain-free) to 100 (worst pain).

Acetaminophen fares better for reducing pain intensity in hip or knee OA (-3.7 points, CI -5.5 to -1.9)-significant statistically, but still not clinically significant.

These results differ from earlier meta-analyses that demonstrated a clinically significant reduction in pain for hip or knee OA with acetaminophen.

The drug is considered safe in doses up to 4,000 mg/day. However, the current study found evidence that patients taking acetaminophen are four times as likely to have abnormal liver tests, although the clinical significance of this is uncertain.

An accompanying editorial points out that the UK's National Institute for Health and Care Excellence first advised against offering acetaminophen, then reversed itself after critics pointed to the potential dangers of alternative drugs. For knee OA pain, the editorial recommends topical non-steroidal anti-inflammatory drugs, such as ibuprofen, which have fewer side effects and are popular with patients.

The UK has not experienced the dramatic increase in prescribing opioids seen in the US, the authors point out. The editorial argues for greater emphasis on the "notoriously difficult" changes in weight and exercise habits, which have proven results.

It won't help patients with knee pain to exercise less painfully if you inject them first with low doses of steroids, the Danish researchers found. Twelve weeks before starting 100 knee OA patients on a 12-week supervised exercise program, they randomized the group to receive either an intra-articular injection of 40 mg methylprednisolone acetate, plus saline or lidocaine, or placebo.

The primary outcome was change in the pain subscale of the Knee Injury and Osteoarthritis Outcome Score (KOOS) questionnaire at week 14.

The mean changes at week 14 were 13.6 in the corticosteroid group and 14.8 points for the placebo patients, not a statistically significant difference. Nor were there statistically significant differences in any secondary outcomes (KOOS subscales and other measurements).

Noting that they had used a low dose of corticosteroids, the authors wonder whether a higher dose might achieve better results.