Diarthrodial joints are freely moveable joint

Joint

A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally.-Classification:...

s held together by a joint capsule, such as the knee

Knee

The knee joint joins the thigh with the leg and consists of two articulations: one between the fibula and tibia, and one between the femur and patella. It is the largest joint in the human body and is very complicated. The knee is a mobile trocho-ginglymus , which permits flexion and extension as...

 and shoulder

Shoulder

The human shoulder is made up of three bones: the clavicle , the scapula , and the humerus as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder make up the shoulder joints. The major joint of the shoulder is the glenohumeral joint, which...

, as opposed to slightly moveable (amphiarthrodial) or immoveable (synarthrodial) joints, such as the spinal

Vertebral column

In human anatomy, the vertebral column is a column usually consisting of 24 articulating vertebrae, and 9 fused vertebrae in the sacrum and the coccyx. It is situated in the dorsal aspect of the torso, separated by intervertebral discs...

 and sutural joints, respectively. http://www.palaeos.com/Vertebrates/Lists/Glossary/GlossaryD.html They are the type of joint most commonly involved in rheumatological disease. The sacroiliac (SI) joints in the pelvic region are an example of a diarthrodial joint