Various media reports have suggested that surgery for knee pain is “a waste of time,” or “does more harm than good.”. If you’re currently considering some kind of knee operation, this sort of headline might make you think twice. Perhaps you’d be better of finding a good physical therapist instead, or just taking some painkillers and trying to work around it.

Regular readers of this column may guess what’s coming next, though. Before we take a closer look at what the evidence says, let’s talk about what we mean by “knee surgery”.

Knee surgery isn’t a thing.

If we’re going to look at the research properly, then it’s important that we’re very clear what we’re actually talking about. “Knee surgery” covers a whole range of different procedures for different problems, and lumping them all together won’t help us to figure out what works and what doesn’t. Worse still, it’s often the case that a particular study focuses only on one kind of procedure, but that detail gets lost somewhere between the press release and the final news report (or is only mentioned briefly towards the end of the article). This is a little bit like dropping a dozen toasters off your roof, and then proclaiming that “machines can’t fly.”

The other problem is that no two people are exactly the same. Even if you’re looking at the same procedure, it’s likely that it will be more effective for some people than others. The difference may depend on the severity of the injury, your age, your lifestyle, and your activity level. It’s often hard to know in advance who will benefit the most from a particular intervention - it may be that some get better, but others get worse. Some research attempts to find factors that help to predict who will benefit from the surgery, or restrict their attention to a group of patients with very specific characteristics; other studies look at the overall outcomes across a wider range of patients. Without taking a close look at the research literature, it’s tricky to know how to interpret many of these findings, and even the experts often reach different conclusions from the same evidence.

What is the evidence being reported on?

The most common kind of knee surgery that’s been under scrutiny recently is arthroscopic (keyhole) surgery for meniscus (cartilage) tears. So, to keep things straightforward, we’ll focus on this and leave aside the many other procedures such as knee replacements or ligament reconstructions.

One study that led to some of the headlines was a systematic review published in the British Medical Journal in 2015. It focused on surgery in middle aged or older patients with knee pain and degenerative knee problems. The review looked at nine original studies that met the authors’ criteria, and it found that overall, there wasn’t much benefit from surgery compared to other interventions, such as anti-inflammatory drugs or exercise therapy. It didn’t take into account whether or not there were “mechanical symptoms” such as joint locking; this means that it’s unclear from this study whether or not surgery will be more helpful patients who experience these. In practice, many specialists do take this into account when making decisions about treatment and some argue that locking of the joint is an indication that surgery is needed.
What about acute injuries?

How do things differ if you’re a young, active person and your meniscus tear isn’t the result of general wear and tear, but occurred in an accident or sports injury?

There’s little research that looks at non-operative management of acute meniscal tears in younger age groups. Whether or not a trial of conservative treatment is advisable is likely to depend on how stable the tear is. A stable tear may settle down by itself, whereas an unstable one can allow the meniscus to move abnormally and may continue to cause problems or progress further.

If surgery is considered, much will depend on the nature of the tear itself. In the past, it was common to remove the whole of the meniscus, but studies have shown that this generally leads to altered biomechanics of the knee, osteoarthritic changes and increases the likelihood of future problems. Nowadays, more emphasis is placed on trying to preserve the meniscus if possible, either by repairing it, or by removing only part of it.

Evidence suggests fairly good results for partial meniscectomy in younger patients (under 40) who don’t have degenerative changes or other accompanying problems (such as tendinopathy or ligament injury).
The trend towards trying to preserve as much of the meniscus as possible has led towards advances in surgical techniques. Meniscal repair requires a longer rehabilitation period than simply removing part of the meniscus; in order to allow it to heal properly, patients may need a period of non- or partial-weight bearing. Is this added inconvenience worth it? Comparing different kinds of surgery is difficult. Surgeons generally weigh up many factors when deciding which procedure to perform, such as the fact that not all tears are suitable for repair, and randomized trials can be problematic to do for a variety of reasons! Although the research is limited, the results that are available so far are promising, and meniscal repair should certainly be considered when the injury is suitable.

The verdict: FALSE. Although there are particular cases where knee surgery can do more harm than good, there are other situations where it is likely to be much more helpful. It’s important to consider each case on its individual merits, and to look carefully at the research that’s most relevant to your own situation instead of just reading the headlines.
 
Whether or not to have surgery can be a difficult decision, and unfortunately there isn’t a straightforward answer, so don’t be afraid to get opinions from several different consultants before you make up your mind (and bear in mind that surgeons may have a bias towards surgery compared to other treatments). If your symptoms are manageable and (in the view of your specialist) the problem is unlikely to get worse by waiting, then it may well be worth trying a program of exercise therapy before deciding on an operation. That’s especially true if the damage is degenerative rather than acute, or if you’re a bit older. Even if you do end up getting the surgery, you’re likely to benefit from having done the rehabilitation work first.