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Find out the causes of knee pain and how it can be treated
The ends of the bones in the knee joint are covered with articular cartilage. This is a smooth material that cushions the bones during movement. Two crescent-shaped structures made out of cartilage, called the lateral meniscus and medial meniscus, sit between the thigh-bone and shin-bone. This rubbery material helps to cushion the joint and keep it stable.
A thin lining, called the synovial membrane, surrounds the joint. It helps to lubricate the cartilage and reduce friction.
Due to its location in the body and the demands placed upon it by normal daily life, the knee joint is a common place to feel pain or suffer injury. The basic function of the joint is to allow movement of the leg in a front to back direction.
However, the knee is in fact a modified hinge joint that allows some rotation. This is needed for two reasons.
First, this rotation allows the knee a degree of extra mobility when performing tasks such as squatting and jogging, especially when changing direction simultaneously. This is essential for the type of movements needed when playing sports.
Second, this small amount of rotation allows the knee joint to be able to lock when fully straight (full extension). You may feel the benefit of this with a healthy knee in standing if you tense your knee muscles to fully straighten your knee. This allows us to stand in a stable position with less effort.
The other unique aspect to the knee is the addition of the kneecap (patella) to the joint anatomy. The patella is present to protect the front of the knee joint when kneeling or if it is struck. However, the other key function of the kneecap is to act as an interim lever to attach the large muscles at the front of the thigh (quadriceps muscles) to the top of the lower leg bone (tibia).
This lever action provides a great deal more force for the quadriceps muscles, which are the main stabiliser and mover of the knee joint during functional tasks. Research has demonstrated that this system increases the quadriceps effectiveness by more than 200% at some angles of knee flexion.
Get even more information on our knee pain hub.
When something goes wrong with the knee, it results in knee joint pain. This may be felt as an inside knee pain or as knee pain after running.
There are two main causes of knee problems, traumatic and overuse/degenerative.
One example of overuse in daily life is the amount of bodyweight that goes through the knee joint during normal daily activities, such as:
The kneecap joint (patellofemoral joint) also experiences huge compression forces during everyday tasks, such as:
These tasks are performed many times each day, so even with the knee joints design to withstand such forces, it is no surprise that the knee joint suffers from an overuse and degenerative pain disorders.
The other factor to consider is the site of the knee located between the ankle and foot, which are often fixed to the ground, and the hip, which allows significant amounts of rotation.
When playing sports, many acute knee injuries are the result of the knee being unable to cope with the rotation placed upon it with the foot fixed to the floor. This can be compounded with the use of studded footwear, which does not allow the foot to pivot.
Other sports-related traumatic knee injuries can occur as a result of a direct impact to the knee by an opponent at an awkward angle. Common examples are being tackled when playing football or direct clashes during heavy contact sports, such as rugby.
Those that are caused by a traumatic injury to the knee, and those that are caused by overuse or a degenerative injury to the knee.
The most common form of traumatic knee injury is a tear to one of the menisci. These act as shock absorbers between the joint surfaces and due to the extreme loads placed upon the knee joint during sports they are prone to injury.
Of the two, the medial meniscus is much more commonly injured than the lateral meniscus. This is because it is attached to other structures on the inside of the knee, which makes it vulnerable when these structures are tensioned.
The common cause of injury is when a sports player turns direction and catches their foot awkwardly in the turf or when the knee buckles on landing awkwardly such as when playing football, netball or basketball.
Pain on the outside of the knee is a common symptom of this type of injury. Other less common but troubling causes of traumatic knee pain are knee ligament injuries.
There are four ligaments around the knee:
Because these structures are closely linked, it is possible to get a meniscal tear and damage the anterior cruciate ligament at the same time.
When this happens, it is called a medial collateral ligament. Inner knee pain is a common symptom of this type of injury. Isolated medial collateral ligament injuries normally occur as a result of inwards impact to the outer side of the knee, such as from an opponent during contact sports.
This forces the knee to deviate inwards and overload the medial collateral ligament, which lies on the inside of the knee. Pain on inner side of knee is a common symptom of this type of injury. Depending on which traumatic injury you have sustained, the location and severity of knee pain may vary.
Symptoms that accompany knee pain include:
Early age-related changes known as osteoarthritis is the most common form of knee pain in middle-aged and elderly individuals. Knee pain when bending and knee pain when walking are both common symptoms that there is something wrong with the knee.
Knee pain due to osteoarthritis is characterised with pain and sometimes intermittent periods of swelling and instability to the knee. The process of osteoarthritis involves a gradual wearing and thinning of cartilage in the joint surfaces as well as a stiffening of the soft tissue within and around the knee joint.
Most commonly, this process affects mainly the inside of the knee known as the medial compartment but can occur in the outer (lateral) knee compartment or the patella-femoral joint simultaneously. Age-related changes to the menisci of the knee also occur.
These may occur in conjunction with more diffuse knee osteoarthritis or independently. These age-related changes can manifest in cysts developing to the edges of the menisci or degenerative tears to the menisci in the absence of any undue trauma.
Sports that involve a lot of straight line running with little side to side or rotational movements can cause knee pain in the kneecap (patellofemoral joint). You may experience back of knee pain or pain behind knee if you are overusing your knee joint.
It is thought that the absence of lateral movements may lead to muscle imbalances at the hip and knee. This in turn increases the load through the patellofemoral joint, which can lead to excessive friction developing on the outer aspect of the knee.
The symptoms of a degenerative condition depend upon the type of arthritis. These symptoms may gradually progress as your condition worsens. However, it is possible that a minor injury will cause the symptoms to worsen.
The most common symptoms of knee arthritis include:
Knee arthritis pain is usually worse after doing an activity, especially with overuse. Your knee may also feel stiff if you have being sitting for a long period.
This precise surgical procedure will depend upon the cause of the knee pain, but the options include soft tissue knee surgery and ligament surgery.
Read more about knee pain and the treatments available on our knee pain hub.