Knee Pain, Conditions & Injury
A closer look at knee anatomy
The knee is more likely to be damaged than most other joints because it is subject to tremendous forces during vigorous activity. The knee is the joint where the femur (thighbone) meets the tibia (lower leg bone). The knee moves like a hinge, but it can also rotate and move from side to side.
The patella (kneecap) is a small, flat, triangular bone in front of the joint. It is not directly connected with any other bone. Muscle and ligaments hold it in place.
The femur and tibia are connected in three ways: by ligaments (strong cord-like tissues), by muscles, and by a capsule. The capsule surrounds the joint (thighbone) and the tibia (large bone of the lower leg) are connected in three ways: by ligaments (strong, cordlike tissues); by muscles; and by a synovial capsule. The synovial capsule surrounds the joint.
The synovial capsule secretes a liquid called synovial fluid, which resembles raw egg white. The synovial fluid nourishes the joint surfaces and reduces friction between them. If the synovial capsule is injured, it may produce too much fluid.The knee ligaments are the strongest connections between the femur and the tibia. Ligaments keep the bones from moving out of position. One group of muscles bends the knee and another group straightens it.
Smooth tissue called cartilage covers the ends of the femur and the tibia. This tissue helps the bones slide easily over each other and is a tissue that is attacked in arthritis.
Common causes of knee pain treated at MOS
Patients with knee pain typically experience swelling, stiffness, weakness or instability in the joint. They may also experience crunching or popping noises or the inability to fully straighten the knee.
Knee pain is most commonly caused by injuries during activities like recreational sports or tasks at work or home. Injuries to the knee may be sudden, such as during a fall, a direct blow to the knee, or abnormally twisting or bending the knee.
Pain, bruising, or swelling may be severe and develop within minutes of a knee injury.
Knee pain can also be caused by overuse of the joint, due to repetitive motions. This is often associated with activities such as climbing stairs, running, jumping, or bicycle riding.
Anterior cruciate ligament (ACL) injuries
The ACL is one of the ligaments in the knee joint that connects the thighbone (femur) with the shinbone (tibia). During an injury, the ACL may become torn, ruptured, or separated from the bone. Symptoms of an ACL injury include pain and swelling on the outside and back of the knee, and instability or limited movement in the knee joint.
Arthritis is painful inflammation and stiffness of the joints, which can be caused by many types of degenerative joint conditions. There are over 100 types of arthritis, including osteoarthritis, rheumatoid, gout, psoriatic, septic, post-traumatic, and lupus. Arthritis symptoms can include swelling, tenderness, sharp pain, stiffness, and sometimes fever and chills.
Bursitis is painful inflammation of the bursae, the fluid-filled sacs that reduce friction between bones, tendons, and muscles. It can be caused by an injury, infection or other condition. Pain may be accompanied by swelling, tenderness or loss of movement.
Bone chips are small fragments of bone or cartilage that break off from the knee joint during an injury. In some cases, the fragment may become lodged in the knee joint, making motion difficult or impossible. Symptoms that indicate the possible presence of bone chips include pain, swelling, and locking in the knee joint.
In the normal process of aging, the cartilage in the knee begins to break down. As the cartilage deteriorates, the bones of the knee joint begin to rub together, causing damage and discomfort. Symptoms include pain and stiffness in the knee joint.
Chronic knee pain
Chronic knee pain is frequently caused by chondromalacia, also known as patellofemoral pain syndrome. Chondromalacia is damage or deterioration of the cartilage underneath the kneecap. A common symptom is pain that worsens when climbing stairs or sitting with the knees bent for long periods of time.
A knee fracture is a break in the bones of the knee joint. This typically happens as a result of trauma, such as a fall, or forceful blow. The kneecap (patella), lower thighbone (femur), or the upper shinbone (tibia ) may be affected in a knee fracture. Symptoms include severe pain, tenderness, and swelling, accompanied by deformity of the knee joint and inability to walk or put weight on the injured leg. In some cases, there may be numbness or weakness below the knee, in the lower leg or foot.
Iliotibial (IT) band syndrome
The iliotibial band is a group of fibrous tissue that runs down the outside of the thigh, providing stability to the knee and hip. IT band syndrome causes the fibers to overdevelop and tighten, causing the band to rub against the bone when the knee is bent. Symptoms include pain on the outside of the knee that improves with stretching or rest.
Ligament injuries & tears
The knee joint has four ligaments: tough, flexible fibers that link the bones together providing stability and controlling movement. Injuries to these ligaments may occur during sports activities or with trauma, such as a blow to the knee. Symptoms include intense pain, swelling, and a loud pop at the moment of injury. It may be difficult to put weight on the affected leg, and the knee joint may feel loose and unstable.
A meniscus is a c-shaped disc of cartilage located between the bones of the knee joint. Meniscus tears are categorized into three groups: minor, moderate, and severe. Symptoms of a minor tear are mild pain and swelling. A moderate tear may swell more over the course of a few days, and sharp pain may occur when squatting or twisting the knee. After a severe tear, pieces of the torn disc interfere with joint function, causing the knee to catch or lock, or making it difficult to straighten.
Osgood-Schlatter disease is inflammation of the tendon that connects the kneecap to the shin, frequently seen in adolescents who are active in sports. Symptoms include a painful bump under the knee, and discomfort that increases when the knee is used.
Osteochondritis dissecans occurs when the blood supply to part of the cartilage or bone in the knee (or other joints) is lost. That portion of cartilage or bone can develop small cracks or even break off entirely. In some cases, the fragment of bone or cartilage may lodge itself in between the bones of the joint, making movement difficult or impossible. Symptoms include pain, swelling, tenderness, and grinding or locking in the knee joint.
Runner’s knee, also known as patellofemoral pain syndrome, is an injury caused by overuse of the knee joint. Symptoms include pain around the kneecap, swelling, and a feeling of grinding in the knee. Pain symptoms may increase when the knee is used, particularly when walking downstairs or on an incline.
Infected knee replacement
A knee replacement can become infected, making knee revision surgery necessary to correct the problem. Infections, though rare (occurring in less than two percent of patients overall), are caused by bacteria traveling through the bloodstream, even years after surgery. Symptoms of an infection include fever, chills, redness or swelling of the knee, and drainage from the surgery site.
Failed knee replacement
Failure of a replacement knee joint is caused by the wear and tear of daily use on the metal or plastic components. Signs that a knee replacement is failing include pain, stiffness, and a feeling of instability. Knee revision surgery may be necessary to correct the problem.
Sprains & strains
Sprains are stretched or torn ligaments, the fibrous bands of tissue in joints that connect bones. Knee sprains are common and can cause pain and swelling and are ranked by three degrees of severity: a slight ligament tear or stretch (first-degree), a partial or incomplete ligament tear (second-degree), or a complete ligament tear or rupture (third-degree).
Strain is a stretched or torn muscle or tendon. Strains cause pain and swelling and are ranked by three degrees of severity: a slight muscle or tendon tear/stretch (first-degree), a partial or incomplete muscle or tendon tear (second-degree), or a complete muscle or tendon tear/rupture (third-degree).
Subluxation or dislocation
Dislocation of the knee occurs when the thighbone (femur) moves out of proper position with the shin bones (tibia and fibula), tearing the ligaments of the knee. Symptoms of knee dislocation include intense pain and swelling, visible deformation, and inability to move the knee. There may also be numbness or tingling in the lower leg or foot.
Subluxation is a partial dislocation that commonly affects the kneecap (patella). Symptoms of subluxation include a feeling that the kneecap is jammed or moved out of place.
Tendonitis (also known as tendinitis) is inflammation of the tendons: the thick, rope-like cords of tissue that connect muscle to bone. Tendonitis is caused by overuse (repetitive motion) or sudden injury. Tendonitis symptoms include pain in the tendon area, and sometimes loss of motion.
A tendon injury is damage that occurs to a tendon, which normally connects a muscle to a bone and allows for flexible motion of the limbs. For example, the Achilles tendon is the tough fiber that links the calf muscle with the heel bone, making jumping and running possible. In a tendon injury, the tissue can become overstretched, develop micro-tears, or rupture. Symptoms of a tendon injury include inflammation, tenderness, and pain that increases during use of the affected area.