When asked what's a joint, most of us answer saying knees, elbows, ankles, etc. are joints. While we all have a fair idea of what joints are, most often we fumble when asked to define what we mean by joints in terms of their physical functions. Therefore, let's start with understanding what joints are. The joints in the body are those skeletal system meeting points where two or more bones. Besides allowing support for movement, these joints also provide mechanical support for such movements. The various types of joints in the human body are categorized in accordance with their structures as well as according to their functions. While joints allow movement along their point of conjunction, not all joints do so. There are certain fixed joints - such as those of the skull - which do not allow any kin of movement along the lines of skeletal contact. Let's get introduced to the all the joints in the human body.
How Many Joints in the Human Body?
Before we proceed towards the various types of joints in the body, let's start with how many joints there are in total. There are about 230 and more joints in an average human body! There may be some difference in this number if compared between a fetus and an adult. You see, a fetus has 300 bones initially but most of them fuse together by the time of birth. An average adult has about 206 bones in total. Coming back to the number of joints, the count can be broken up as follows:
|Distribution of Human Body Joints|
|Part of the Body||Number of Joints|
|Throat and Neck||6|
|Spine and Pelvis||76|
|Hands, Arms and Fingers||64|
|Legs, Feet and Toes||62|
Note: The description of the joints is debatable hence, stating the exact number of joints is not possible. It is believed that the average number of joints in the human body lies between 200-400. The anatomy of the body varies from person to person and age is one of the factors responsible for it. As our body develops, the bones are integrated and thus, the number of joints are also reduced. Considering the above table, the joints in the neck are also part of the spine and the thorax as well. So interpreting the addition of the above figures as the total number of joints in the body is not recommended.
Types of Joints in the Human Body
Joints can be classified in accordance with various bases such as type of movement imparted, functions, structure, etc. Let's take a look at these various types of joints and their different classifications.
Classification According to Movement Imparted
- Ball and Socket Joints (shoulders and hips)
- Hinge Joints (knees and ulna of the elbows)
- Condyloid Joints (jaw and fingers)
- Gliding Joints (spine, wrists and ankles)
- Pivot Joints (neck and radius of elbows)
- Saddle Joints (thumbs)
Classification According to Structure
- Fibrous Joints (sutures, syndesmoses and gomphosis)
- Cartilaginous Joints (synchondroses and symphyses)
- Synovial Joints (wrist carpals, acromioclavicular joint, elbow area between humerus and ulna, Atlanto-axial joint, proximal radio-ulnar joint, distal radio-ulnar joint, wrist joint, carpometacarpal thumb joint, Glenohumeral shoulder joint, hip joint, sternoclavicular joint, knee-joint)
Classification According to Function
- Synarthrosis (allow very limited or no mobility such as gomphosis, synostoses and synchondrosis; mostly fibrous joints.)
- Amphiarthrosis (Allow somewhat limited mobility such as symphysis, syndesmosis and interosseous membrane; mostly cartilaginous joints)
- Diarthrosis (enables a wide variety of movements and all synovial joints come under this classification)
Classification According to Anatomical Location
- Articulation Joints of the Hands
- Wrist Joints
- Elbow Joints
- Axillary Shoulder Joints (Glenohumeral and acromioclavicular joints)
- Sternoclavicular Joints
- Vertebral Articulatory Joints
- Sacroiliac Joint of the pelvis
- Temporomandibular Joint of the jaw
- Articulation Joints of the Feet
- Hip Joints
- Knee Joints
The anatomical classification of joints can be further sub-classified under simple, compound and complicated joints, based upon the number of bones involved in each joint and their individual biomechanical properties. For instance, the lesser bones involved, the simpler the joint is, and the more bones involved, the more complex it becomes.
That was a brief rendezvous with almost all types of joints in the human body. One of the most notorious and painful ailments to attack joints is Arthritis. It mostly attacks the joints in old age but these days, many young people are also falling victims to this affliction due to unhealthy posture and sedentary lifestyle. Bad habits such as cracking joints may also lead to joint pain and joint swelling. A good healthy diet and some light, regular exercise may go a long way in giving you healthy joints and keeping conditions such as stiff joints, sore joints, etc. at bay well into ripe age. Hence, stay active for agile joints!