Each joint of the body is made up of 2 or more bones each of which is covered in a layer of cartilage to improve friction between the two. Knee osteoarthritis is where the cartilage of the knee joint begins to wear thin due to being used The cartilage on the inside of the knee is most commonly damaged due to the knee using the inside of the knee as the axis it rotates around. The pain from knee osteoarthritis is usually felt as a deep unspecific pain due to the cartilage and bone of the knee not having precise mapping in the brain, so our body struggles to pin point the exact cause of pain. The pain is usually accompanied by stiffness in the joint usually most pronounced in the morning and easing once we get moving.
The knee cap runs in a groove in the middle of the femur. Patellofemoral pain syndrome is caused by maltracking of the knee cap, where the knee cap does not run straight in the femoral groove but rather it rubs on the side of it. Patellofemoral pain syndrome is usually caused by leg biomechanics that causes the knee to rotate inwards, usually caused by weakness at the gluteus medius muscle in the hip and vastsus medialis muscle in the quadricep. The damaged area is the cartilage overlying the bone of the femur, this does not always give the most precise location of pain and so patellofemoral pain can be felt as a broad feeling of deep knee pain.
Jumpers knee also known as patella tendinopathy is where the tendon joining the knee cap to the shin is overworked, damaged and inflamed. Patella tendinopathy usually happens when there is repeated large amounts of force placed on it in a short about of time such as when lading from a jump. The pain is felt below the knee cap and is localised to the tendon itself, the pain is increased anytime the tendon is loaded such as getting out of a chair.
The meniscuses are a thin layer of connective tissue that lie between the two bones of the knee, they help dampen the forces going directly into the bone of the knee. Meniscal tears usually occur when when we have have aggressive knee rotation such as cutting movements in sports that cause the femur of the leg to rotate against the meniscus causing it to tear. Although meniscal tears are common in sports and have there origin in a single high energy event the meniscus can also be worn down gradually, this meniscal degeneration may present very similar to knee osteoarthritis.