We’re all familiar with infections. A nick while gardening. The sudden swelling and redness. A trip to the GP if things unexpectedly deteriorate.
Knees, of course, can become infected like any other part of our bodies. And not just because of the familiar graze or wound after an injury. A serious knee infection – particularly one that gets into the joint – is a genuine medical emergency.
Here’s how that typically happens – and what we can do if it does.
3 main types of infection
There are three principal ways that patients tend to present with knee infections. Some have the potential to be more difficult to treat than others:
Cellulitis
This is probably the most common type of infection where knees are concerned. It’s usually caused by bacteria like streptococcus and staphylococcus, which are often present on the surface of our skin. If you cut yourself, these bacteria can enter through the abrasion and start to cause problems. You would typically see a spreading redness over the kneecap area. This might be followed by heat and some swelling. It could also become painful to the touch. Like other infections, cellulitis can develop into more serious conditions if left unchecked. Once diagnosed, cellulitis usually responds well to a course of oral antibiotics; severe cases, or infections that don’t respond to oral antibiotics, sometimes require intravenous antibiotics.
Prepatellar bursitis
Bursitis is what happens when a bursa – one of the thin “sacs” near our joints that prevent friction between tissues and bones – suddenly swells up and becomes tender, red and sometimes stiff to move. What’s happening is that the knee is releasing more fluid to protect the area from an external assault. That assault could be irritation from a fall, or repeated kneeling (roofers and tilers are particularly vulnerable, for instance). Or it could happen when bacteria get under the skin and take up residence in the bursa. Bursitis is usually diagnosed by performing an aspiration (draining some fluid from the knee so it can be analysed in a lab). Like cellulitis, it usually responds well to oral antibiotics, though more severe infections may need to be treated with intravenous antibiotics.
Septic arthritis
This is one of the most serious types of knee infection. The cause is usually bacteria, or a virus, entering through a wound near the knee, though it can transfer to the joint via the blood from somewhere quite different – after an injection, surgery and even toothbrushing. The problem with septic arthritis is that when the infection gets into the interior of the joint, it can be difficult to fight off (especially if the patient is already immunocompromised). Septic arthritis can cause sudden and severe symptoms, including swelling, redness and severe pain. You could feel sick and feverish as well. This type of infection needs to be treated immediately. Among other things, it can cause significant damage to the lining cartilage in the knee, sometimes within hours. Treatment involves aspirating the knee, with arthroscopic or open washout of the joint to eradicate bacteria. This would be accompanied by broad-spectrum antibiotics through an intravenous drip and several weeks of oral antibiotics. Septic arthritis is treated in hospital; the average patient will need to stay in hospital for around two weeks.
When to seek help
Does a red, swollen knee usually mean infection? Absolutely not. There are many different reasons why you might experience symptoms like these, and infection is one of the rarer ones. That said, because knee infections are potentially very serious, it’s important to rule them out – particularly if you’ve recently had surgery, suffered a wound injury, or if the pain or inflammation seems to be getting worse or you’re feeling unwell. The NHS advise you to ask for an urgent GP appointment or get help from NHS 111 if:
- you have severe joint pain, usually in just one joint, that started suddenly
- you have swelling around a joint
- the skin around a joint has changed colour
- you feel generally unwell and have a high temperature or feel hot and shivery
The good news is that there are plenty of arrows in the medical quiver when it comes to treating a knee infection effectively. The key thing, though, is to get seen and treated sooner rather than later.
Are you suffering from persistent knee pain? If so, it’s important to have it properly investigated. You can do that here in the clinic by booking an appointment with us. We’ll make sure you’re seen, examined and treated as soon as possible.
