The knee is the largest joint in the body and, clearly, is one of the most important. It allows us to walk, run, sprint and change direction, all while supporting our body’s weight. It takes a huge amount of pressure throughout our lives and, unfortunately, often starts to fail as we get older, leading to issues such as knee arthritis. It is also vulnerable to injury during sporting and athletic activities.

Anatomy of the knee

The knee joint is, in essence, two bones sitting on top of one another, the thigh bone (femur) and the shin bone (tibia). The kneecap (patella) is found in front of the knee and runs up and down in a groove (trochlea) in the femur.

Cartilage: A protective layer

As with any other joint where a bone touches (articulates) with another bone, we have a layer of white, shiny cartilage over the ends of the bones. This helps them slide smoothly over one another and is called articular cartilage. Within the knee, we also have 2 additional discs of cartilage, which add stability and act as shock absorbers in the joint. These are known as the medial (on the inside) meniscus and the lateral (on the outside) meniscus.

Ligaments: Holding it all together

As the knee is made up of two bones sitting on top of each other it is inherently unstable. The menisci do help with the stability of the joint, but the main strength comes from the ligaments. We have two ligaments that cross over each other inside the joint called the anterior and posterior cruciate ligaments. We also have two that run up either side of the joint, called the medial and lateral collateral ligaments. When force goes through the joint and potentially puts it under strain, the ligaments tighten to support it.

Muscles: Pulling power

As well as the ligaments, muscles associated with the knee help support the joint and keep us stable. However, the main function of the muscles is to contract, some in one direction, some in another, This is what causes our legs to bend or straighten. These movements in the knee are called flexion (bending or flexing) and extension (straightening or extending). The muscles which extend the knee are the quadriceps, and the main muscles which flex the knee are the hamstrings (which you often hear about when athletes are injured). It is vital that these muscles are working well for the joint to function properly.

• Torn meniscus – the discs of cartilage are damaged or torn when the femur rotates on the tibia. This can be an acute injury which is extremely painful and can cause the knee to lock or, more often, create a degenerative tear which slowly becomes more and more of a problem. A tear of the medial meniscus is much more common than the lateral and will give you pain on the inside of your knee.
• Medial collateral ligament (MCL) injury – this injury occurs when the knee is forced inwards putting stress on the inside of the knee. We grade ligament injuries from 1 to 3. A grade 1 injury involves just a few fibres of the ligament causing pain and discomfort. A grade 3 would be classed as a complete rupture, an injury at least as serious as a broken bone.
• Anterior cruciate ligament (ACL) injury – as with the MCL, there is usually one-off incident injuring the ACL, which doesn’t always have to be in a tackle or involve contact. It could be a twisting injury, for instance, whilst landing from a jump, or falling when skiing when the binding doesn’t release.
• Knee arthritis – often age-related, this involves the articular cartilage over the ends of the bones wearing away. This happens with time and can give different levels of symptoms depending on the severity of the changes.
• Anterior knee pain – pain felt over the front of the knee is very common, especially in teenagers, but we don’t always know the exact source of the pain. Examination of the quadriceps to check they are working and supporting the patella is always where to start diagnosis and treatment.  Assessment of a patient’s biomechanics and how their glutes are working to is also very important.
• Patella tendinopathy (commonly called tendonitis) – this is caused by a sustained overload or jarring through the patella tendon at the front of the knee. This condition is commonly seen in sports that involve a lot of jumping.
• Patella dislocation – this will always involve some form of trauma, causing the kneecap to pop out of the groove it normally sits in.

If you have knee pain, knee arthritis or your knee is having an impact on your daily life and activity, please get in touch. The team at Bridge Health & Wellbeing have a great deal of experience treating many knee conditions. To speak to our physiotherapist Paul or book your physiotherapy appointment at our health and wellness centre on Bridge Street in Christchurch, Dorset, please contact us on 01202 473800 or email info@bridgehw.com.

Paul O’Connell (MSC, BSC, HCPC, MCSP) is a physiotherapist with two decades of clinical expertise. He has worked right across the UK, from North Yorkshire and London to Hampshire and Dorset. Sports medicine is one of his areas of special interest: he has worked both on the touchline and in sports injuries clinics, and now lectures on the Sports Therapy programme at Bournemouth University. Having spent several years managing physiotherapy and health assessment teams in two key Nuffield Health hospitals, Paul also has an extensive understanding of orthopaedic surgery.