According to Sport England, more people are signing up to marathon events and the number of weekly runners in England rose by 63,000 to 2.1 million in 2015. But with greater numbers of you pounding the pavements, are you taking adequate precautions to protect yourselves against injury?
Various studies have shown that between 30 - 50% of runners will suffer an injury in a training year, with 40% of those injuries affecting the knee, so the important thing to do is to listen to your knees. 'No pain, no gain' may be right for cardio fitness training or strength training, but when it comes to joints, pain is normally a sign of a problem. It can be dangerous to just ignore knee pain, and potentially even more dangerous and damaging to take painkillers or anti-inflammatories and just soldier on regardless.
Even with the best footwear, the best posture and the best training and conditioning, the forces on the cartilage covering the back of the kneecap and the groove in the middle of the front of the knee when you land on one leg with the knee slightly bent can be up to seven times your bodyweight, which is massive.
The majority of knee pain in people training for a marathon is from overload of the tissues due to overuse. The best way to avoid this is to take plenty of time to gradually build up your training and avoid ramping things up too fast, in order to allow your body time to adapt appropriately to the increased stresses that you're putting it through. Having the best possible footwear is also essential, but If you're new to running and if you've got any concerns, then the gold standard is to have video gait analysis performed by a qualified physiotherapist or specialist biomechanist. Many people have all kinds of bad habits or postural deficiencies that can respond very well to appropriate retraining.
The two big red flags that should make someone concerned about a possible knee issue are pain and swelling. In particular, if a joint swells up intermittently with heavy use then this can be a sign of damage to the articular cartilage, which doesn't have a blood supply and hence it doesn't repair or regenerate itself. This is something that's only ever going to get worse with time and you should therefore get any pain and swelling checked out as soon as possible. Importantly, X-rays will only show up fractures or more severe joint damage -- if you want to check the state of the cartilage in a joint properly, then you're going to need an MRI scan (preferably a high-res high quality 3T MRI).
In terms of the specific injuries sustained, some people overload their tendons and develop inflammation (tendonitis) or degeneration (tendinosis). Other people may develop inflammation from tissues rubbing either inside the joint (such as Medial Plica Syndrome) or on the outside of the joint (e.g. Iliotibial Band Friction Syndrome). These conditions normally settle with rest plus time, but physiotherapy normally helps people recover quicker, and is often extremely helpful. In some cases the symptoms might persist, and if they're bad enough then you might need an ultrasound-guided steroid (cortisone) injection, which is a very powerful anti-inflammatory. Occasionally, in more severe cases that just won't settle, it might even be necessary to resort to surgery.
For those 30-50% of runners who are unlucky enough to sustain an injury, the golden question I always get asked by every runner is 'can I still run?' This depends entirely on the potential damage in the knee joint. If there's no major damage then it's normally fine to continue with running, even if you might have to reduce the mileage a bit and perhaps cross-train with other gentler non-impact exercises such as cycling, the cross-trainer or swimming. However, if there is any significant damage in the knee joint then the question that people really ought to be asking is not 'can I run?' but rather 'should I run?', and unfortunately the answer to this is often a 'no'.
If there is significant knee damage present then continuing with your running can be a bit like a smoker with lung damage continuing to smoke, or a drinker with liver damage continuing to drink. All too often this just simply isn't what runners want to hear -- and a sure fire way to make a runner hate you is to tell them to stop running! (and if you do, then a lot of the time they just ignore you anyway!). The important thing is to take any potential symptoms that you might have seriously, and do yourself a very big favour by getting them checked out by either a physiotherapist or a specialist knee surgeon sooner rather than later.