As the biggest and most complex joint of the body it is not surprising that knee injury is one of the more common conditions encountered by physiotherapists. Walking upright defines the humanoid lineage, so it pays to firstly consider the forces that go through the knee during different activities. One study looking at the knee kinetics during normal stair climbing found that forces on one of the knee joints was up to eight times higher when ascending stairs, compared to walking on level ground.
The components of a knee
There are four major bones in the knee, the femur, the tibia, the fibula and the patella, and two joints, the tibiofemoral joint, which joins the tibia to the femur and the patellofemoral joint which joins the kneecap to the femur.
There are four major ligaments, the medial and lateral collateral ligaments (MCL & LCL), which give stability to the inner and outer parts of the knee. The anterior and posterior cruciate ligament (ACL & PCL) are located in the centre of the knee and prevent excessive forward movement of the tibia and excessive backward shifting of the knee.
Also each knee contains an inner and an outer thick rubber-like pad of cartilage tissue called meniscus. These are crucial to the function of the knee, as they act like a shock absorber, whilst decreasing the contact area between the bones of the leg. The meniscus are able to spread the force from the weight of the body over a larger area, as well as help the ligaments with the stability of the knee.
Add to this tendons and the muscles they are connected to, plus the nerves and blood vessels, and you have a very intricate structure where a multitude of conditions can arise. Looking at diagrams to understand the knee structure can be confusing, so this animated knee anatomy tutorial may clarify the relationship better between the bones, joints, ligaments, and the rest of the knee structure.
Knee injury and treatment
Understanding the physiology of this joint, may help in appreciating not only why knee injury is so common, but also the reason for there being so many types of injuries to the knee. From serious injuries such as meniscal and ACL tears, to conditions like baker’s cyst and runner’s knee, pain can originate from a variety of sources, and differ in the degree of severity.
If you do sustain a knee injury, remember that prompt attention will increase the chances and speed of recovery. Start by stopping the activity that lead to the injury and rest the knee in a elevated position. Use an ice pack, especially if there is swelling or severe pain, and apply for fifteen minutes every couple of hours. When resting the knee a bandage can be used to compress the area to both immobilise the joint and reduce swelling. It is important not to apply heat to or massage the knee injury. All of this should happen in the first few days of the injury, after which a physiotherapist can be consulted if the condition of the knee has not improved.
After an initial physiotherapy assessment of the knee injury, treatment may involve taping and the prescription of exercises for increasing mobility and strength, or further investigation may be required in the form of an x-ray, CT scan, Ultrasound or MRI. Depending on the type of injury, rehabilitation techniques may also be used and in some cases, referral to a specialist or doctor may be required. In some situations this may lead to surgery after which exercise rehabilitation can be conducted by a physiotherapist. In some cases exercise alone may show positive effects over surgery. Regardless the complex structure of the knee means careful assessment and diligent exercise are paramount to a sustained knee injury recovery.
Exercises for knee strengthening
Knee injury or not, devoting some time to proactively strengthen and stabilise the knee, will literally place you in good stead.
Whether you participate in a sport prone to knee injury or want to create a proactive exercise routine, there are a variety of exercises that can be performed to suit your physical level. They range from the simple exercises such as, step ups onto a raised platform, and hamstring curls with the aid of a chair, through to wall squats and side leg raises. There are plenty of resources available and if you are recovering from injury then your physiotherapist can guide you through more specific exercises to meet your goals.
Some sports are more prone to knee injury such as skiing, soccer, gymnastics and hockey. One sport organisation, Netball Australia, is aiming to reduce the incidence of knee injuries by 70 percent through their KNEE program. They have some great examples of warmups and routines that can help build strength, balance and agility. Although specific to netball it illustrates the variety of exercise that can be employed, to build resilience in the knee using a controlled exercise environment.
Even if you are not participating in a sport that has a high risk of knee injury, using exercises to increase the strength and stability of the knee area will help your general health. Strong knees will enable you to do the activities that you love and reduce the chances of muscle strain and falling. It is also worth investigating the type of footwear you wear, as a poorly chosen shoe can instigate or exacerbate a knee injury.
Of course one of the benefits of exercise will hopefully be weight loss, which in turn has the bonus of reducing stress on the knee. A study regarding weight loss and reducing knee-joint loads in overweight adults with knee osteoarthritis found that each pound of weight lost resulted in a four fold ‘reduction in the load exerted on the knee per step during daily activities’. Add to that a recent publication in the Medical Journal of Australia highlighting that increased body fat is associated with osteoarthritis and it is clear that losing weight will also benefit the knee, not just in reducing joint stress but also by increasing the health of the knee joint.