Common Causes of Knee Pain

Osteoarthritis

The cartilage starts to wear away over time. In extreme cases, the cartilage can completely wear away, leaving nothing to protect the bones in a joint, causing bone-on-bone contact. Over time this may lead to a bowleg or knock knee deformity.
Symptoms include pain, grinding, difficulty walking. Depending upon the location of the arthritis patients may have pain only with stairs or getting out of chairs.

Chrondromalacia Patella

The cartilage on the undersurface of the kneecap (patella) begins to soften. This is caused by rubbing together of the patella and femur (thighbone). This is more common is young athletes.
Symptoms include an aching deep pain while bending the knee.

Rheumatoid Arthritis (RA)

This is an auto-immune disease in which the body’s immune system (the body’s way of fighting infection) attacks healthy joints, tissues, and organs. It can cause pain, stiffness, swelling, and loss of function in joints. When severe, rheumatoid arthritis can deform, or change, a joint. For example, the joints in a person’s finger can become deformed, causing the finger to bend or curve.
Rheumatoid Arthritis affects mostly joints of the hands and feet and tends to be symmetrical. This means the disease affects the same joints on both sides of the body (both the hands or both feet) at the same time and with the same symptoms. No other form of arthritis is symmetrical. About two to three times as many women as men have this disease.

Tendinitis:

This is an inflammation of the tendon. Tendons connect muscles to bones. As muscles contract they pull on the tendon allowing movement. When they are inflamed this movement will become painful. The two large tendons around the knee are the Quadriceps and patella tendons. The Quadriceps tendon is above your knee cap and patellar tendon is below.
Symptoms include pain in the front of the knee practically with movement.

Prepatellar Bursitis.

Bursitis is an inflammation of the bursa in your knee. The bursa is fluid filled sac around your knee joint. The bursa reduce friction in-between your bones and tendons. The most commonly inflamed bursa in your knee is located on top of your knee cap.
Symptoms include swelling and pain on top of your kneecap.

Baker’s Cyst

A baker’s cyst is a fluid filled cyst behind the knee. Often arthritis or a meniscus tear will cause an over production of synovial fluid with in the knee joint. This fluid will drain and fill the cyst.
Symptoms include pain, swelling and tightness behind the knee. This is worse with activity and straightening the knee.

Meniscus Tear

The meniscus are thin C-shaped layers of fibrocartilage, in-between your thighbone (femur) and shinbone (tibia).
The menisci act as shock absorbers, protecting the articular surface of the tibia as well as assisting in rotation of the knee. As secondary stabilizers, the intact menisci interact with the stabilizing function of the ligaments and are most effective when the surrounding ligaments are intact.
Meniscal tears are often the result of a twisting injury. Symptoms include a pop, swelling, pain along inside or outside of the knee. Worse with squatting or bending the knee. You may experience a locking or inability to bend your knee.

Ligament tears

Ligaments are band of tissue that connects bone to bone. The four main ligaments in your knee are the Anterior Cruciate Ligament (ACL), Posterior Cruciate Ligament(PCL), Lateral collateral ligament (LCL), and Medical Collateral ligament (MCL).
Ligament injuries often occur with a painful pop, followed by swelling with-in 24 hours. You may have difficultly putting weight on the knee and a feeling of instability.

Fracture

A fracture is when a bone is cracked or broken. It is a break in the continuity of the bone. Typically the result of injury. However they may result from overuse, osteoprosis, or tumor.

The four bones of the knee are the femur (thighbone), tibia (shinbone), patella (knee cap) and fibula
Symptoms of a fracture include: Pain, swelling, difficulty bearing weight, bruising, and difficulty bending the knee.