Weak knees. Patellar instability. Knee wobble… There are a few different ways to describe an unstable knee joint. But it’s not hard to mistake the symptoms.
To most people, it’s an unsettling feeling of looseness that wasn’t there before. In certain positions, particularly going up or down stairs, you feel as if your knee won’t hold your bodyweight. At times it actually does give way. Or you feel as if it might. You have the sense that you just can’t rely on your knee anymore.
What’s going on? The knee is a complex joint, so instability can have a number of underlying causes. But some are more common than others. Broadly speaking, many of the cases we see here in the clinic fall into one of these three categories…
Muscle weakness
If you’ve ever seen a model of the knee, you can probably visualise how muscles, tendons and ligaments run through, and cross over, the joint. In combination, these soft tissues provide both stability and flexibility to your knee, rather like the tautened guy ropes on a tent. It follows that if some of those guy ropes become too slack (in medical terms, this is known as increased laxity) the whole structure can suffer. This is something that can happen quite easily after a lay-off. That might be because you’ve sustained an injury. Or perhaps you recently had an operation that has made you less mobile. The net effect is that your muscles – particularly the quadriceps, hamstrings and glutes – become weaker. The tension, coordination and control decline. And this can result in a loose and unstable knee joint. Treatment for this kind of instability will usually involve some targeted physiotherapy and a programme of strengthening exercises.
Meniscus tear
The meniscus is the tough pad of fibrocartilage that sits between your thighbone and shinbone. It’s susceptible to damage, either through an accident (trauma) or through the wear-and-tear of ageing (degeneration). (Degenerative meniscal damage is actually more common than you might think: up to 40% of people over 65 are thought to be carrying a tear of this kind.) A serious meniscus tear can cause the whole knee to become unstable or unreliable. Sometimes, little fragments of tissue can become caught in the knee joint itself. If this happens, you might feel as though something is moving around and catching inside the knee, and this contributes to the feeling of instability through the whole joint.
Ligament rupture
Third on our list, but this is perhaps the most significant injury in terms of impact. Ligament rupture means significant damage to one of the four key connective tissues within the knee joint. That’s the Anterior Cruciate Ligament (ACL), the Medial Collateral Ligament (MCL), the Posterior Cruciate Ligament (PCL) and the Lateral Collateral Ligament (LCL) – and roughly in that order, in terms of injury likelihood. Each of these ligaments behaves slightly differently when ruptured. An MCL can be initially unstable, but then recover. The ACL is more likely to lead to ongoing instability. But because the ligaments are responsible for keeping your knee stable and moving smoothly, they can cause significant stability issues when something goes wrong.
What should you do about an unstable knee?
People often think the very worst about knee instability – especially when it’s happening for the first time. The truth, though, is usually much more reassuring. Most types of instability have a fairly straightforward cause, and are generally easy to rectify. If your instability persists or is worrying you, it’s worth seeing a doctor to work out what’s going on. The root cause may be very clear – a twisting injury on the football field, for example. But it could equally be something less obvious, like an old injury that hasn’t been properly diagnosed. Once we have a better idea of what’s going on within the joint, we’ll be able to help you take the next steps towards managing the problem – and getting you back on steady feet again.
Interested in reading more about this topic? You may find these articles helpful…
The top 5 causes of knee pain
How do you repair a torn meniscus?
What is an ACL tear?
How serious is a dislocated kneecap?
What causes noisy, clicking knees?
