Torn ACL: What are the pros and cons of surgery?

The study included 121 athletes with torn ACL injuries. They were aged between 18 and 35 years. More than half of them had also injured one meniscus or both.

People were not included in the study if other ligaments in their knee (the medial or lateral collateral ligament or posterior cruciate ligament) were torn too – or if their knee was very unstable due to injury of the medial or lateral collateral ligament. They were also not included if they had certain types of torn meniscus injuries that had been sewn. This is because people with a stitched meniscus often have to rest their leg for quite a long time and need different rehabilitation treatments.

All of the study participants were randomly assigned to one of two groups. This approach allows for a fair comparison.

• 62 of the participants had surgery where the ACL was replaced with a piece of tendon tissue from their own body. After surgery, the participants had 24 weeks of rehabilitation.
• 59 participants had conservative treatment. They had 24 weeks of rehabilitation too. But they also had the option of deciding to have surgery later.

In both groups, the goal of rehabilitation was to restore the normal range of motion of the knee, strengthen muscles, and improve the knee function. The rehabilitation included strengthening and range-of-motion exercises, as well as various exercises to improve coordination and balance.

The researchers examined and compared different treatment outcomes that are important for people with a torn ACL injury:

• Improvement in symptoms
• Ability to do sports
• Side effects and late complications (for example, the likelihood of later developing osteoarthritis of the knee)

To record the participants' knee problems and symptoms, they answered questions about four main types:

• Pain during various activities like running, kneeling and jumping
• Symptoms like swelling and reduced range of motion
• Knee function during sports and leisure activities
• Subjective problems like lack of confidence in the knee or the need to modify activities due to knee problems

The study results show that both treatment approaches are successful over the long term. In the study, the treatments relieved pain and other symptoms so well that there were hardly any differences compared to people with healthy knees. The knee function during sports was only slightly worse than in people with healthy knees. Subjective knee problems were a little more common, though.

The results of the study are shown in the illustration below. Knee symptoms and knee function were rated on a scale of 0 to 100, where

• 0 = extreme symptoms and
• 100 = no symptoms at all.

The study also found that:

• 50% of the participants who first had conservative treatment later decided to have surgery after all.
• About 25% of the participants developed signs of osteoarthritis that could be seen in an x-ray within five years – regardless of whether they had conservative or surgical treatment. This result is not very reliable, though, because there were so few participants in the study and osteoarthritis can develop over many decades.

No long-term differences between the treatment groups were found. Instead, the advantages and disadvantages of the two treatment approaches result from the type of treatment:

The study results can help you to weigh the advantages and disadvantages of the two treatment approaches. When making the right decision for yourself, other factors play a role too – for example, your sport-specific goals, how unstable your knee is after the ACL tear, and whether other parts of the knee are injured too. It is best to talk about the pros and cons of the different options with your doctor.

The possible complications of ACL surgery include knee joint infections, deep vein thrombosis, and pulmonary (lung) embolism. The new ACL might tear, too. Then further surgery is usually needed.

The Swedish study was too small to reliably say how common these complications are. But other studies have provided estimates. The following table gives an overview:

Other complications, like nerve damage or problems attaching the graft tissue, are very rare.

The Swedish study is the only conclusive study that has compared conservative treatment with surgery in people who have an acute torn ACL. Similar studies are now being done in the Netherlands and the USA. Their results are expected in the next few years.

The limited research leaves several questions unanswered, including:

• Do the pros and cons differ in different groups of people – for example, in children and teenagers, older people, or less athletic people?
• Are there long-term differences between the treatments – for instance, in the risk of getting osteoarthritis later?

These questions can’t be reliably answered yet. As a result, medical professionals sometimes have very different opinions about these things.