Many different types of diseases and injuries can cause knee pain. Tendons, ligaments, bones and other connective tissues work together to form your knee joint, the largest joint in the human body. Your knee absorbs about twice your body weight during normal walking and at least four times your body weight during sports activities. Knee pain can be due to a chronic condition or the result of a sudden abrupt joint injury. Injuries, arthritis, certain diseases and syndromes are the most common causes of knee pain.
Physiology of the Knee
Your knee contains four bones partially covered with protective cartilage. Also, cartilage pads called menisci lie between your thigh bones and you shin bones. Bone cartilage provides a smooth surface for bones to slide during movement and the menisci protect the cartilage by partially absorbing shock to the bones. Lastly, ligaments and tendons hold the bones and muscles together to form your knee joint. The stability of your knee joint depends on the combined efforts of all these tissues working together.
Knee Pain from Injuries
- Strain or sprain
- Meniscal tears
Strains and sprains differ in that a strain occurs in muscle, while a sprain affects ligaments or tendons. Strengthening muscles and tendons slowly can prevent strains and sprains that cause knee pain. A swollen and bruised sprain may be a torn ligament or tendon. The anterior cruciate ligament and the medial collateral ligament are the most commonly injured knee ligaments in sports medicine, which account for more than 50,000 hospital admissions for repair each year.
The menisci can be easily injured during knee rotation while bearing weight. As the foot stays planted, knee rotation may cause partial or total tears of the menisci. With meniscal tearing, the pain is felt most often when the knee is straightened. The pain can range from mild small tears, to severe mobile fragments with swelling. Meniscal tears frequently require surgical treatment.
Accidental large fractures, as well as small stress fractures, can cause knee pain. If a bone is dislocated from its normal position, pain occurs due to bone misalignment. Chondromalacia is a degenerative condition of the kneecap where chronic wear of your kneecap rubbing, instead of sliding, on bone will cause knee cartilage damage and resultant pain.
Arthritis and Knee Pain
A multitude of arthritis types exist as the cause of knee pain. Normal wear and tear that affects the knees of older individuals is called osteoarthritis. As cartilage wears away the pain increases. Rheumatoid arthritis causes inflammation of tissues within body joints, which causes knee pain. Crystalline arthritis, or gout, causes knee pain from sodium urate crystals forming within a joint. Other rheumatic diseases, such as lupus, ankylosing spondylitis and psoriatic arthritis, may cause knee pain as well.
Other Diseases and Syndromes Causing Knee Pain
Osgood-Schlatter disease is pain caused by repetitive stresses placed on the growth area of the upper shin bone. The tendon that holds the kneecap in place becomes inflamed and causes knee pain. It usually occurs in active children 10 to 15 years old and may recur until the child stops growing. Iliotibial band syndrome causes pain when a band of tissue rubs over an outer section of bone and causes inflammation. It is usually localized and the pain is felt from the knee up through the thigh. Another syndrome causing knee pain is plica syndrome. In plica, bands of joint tissue called plicae, retained from fetal development, become irritated from overuse.