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Hand Joints are a complex system that involves the Joint System in the hands and fingers. There are three different set of joints and four overall. There are 3 sets of joints in the fingers, and one in the hand.

The four main fingers have somewhat different muscles and ligaments involved in flexion and extension and other functions. The thumb has its own set of muscles and ligaments. The thumb also has one less joint when compared to the other fingers.

The joints involved in the hand are:

1.)  Carpometacarpal Joints:

2.)  Metacarpophalangeal Joints  (MCP)

3.)  Interphalangeal Joints:

Carpometacarpal Joints:

–  There are 5 Carpometacarpal joints in the hand.
–  The first joint – thumb is a saddle like.
–  The other 4 are Synovial Ellipsoid joints and are slightly different than the thumb.
–  This joint connects the Connect carpal bones (Hand) to Metacarpal bones (Finger)
–  They are joined at the Intermetacarpal Joints
–  The Intermetacarpal Joints: The bases of the 2nd, 3rd, 4th, and 5th metacarpal (finger) bones articulate with one another by surfaces covered with cartilage.
–  The bones are connected by dorsal, palmar, and interosseous ligaments.
–  The Dorsal Metacarpal Ligaments  (ligamenta metacarpalia dorsalia) and Palmar Metacarpal Ligaments (ligamenta metacarpalia palmaria) interconnect transversely from one bone to another on both the dorsal and palmar surfaces.
–  The Interosseous Metacarpal Ligaments (ligamenta metacarpalia interossea) connects their surfaces just distal to their collateral articular facets

Thumb

–  Held in place by 3 main ligaments: Lateral, Aneterior (Palmar) and Posterior (Dorsal)
–  There is a synovial membrane that lines the joint capsule
–  This joint receives blood supply from radial artery and the nerve the innervates it is from the posterior interosseous nerve.
–  Movement of this joint includes: Flexion, Extension, Adduction, Abduction, and Circumfuction.

Muscles involved in movement:

–  Flexion:  Flexor pollicis brevis, Opponens pollicis and Flexor pollicis longus
–  Extension:  Abductor pollicis longus, Extensor pollicis longus, Extensor pollicis brevis
–  Abduction:  Abductor pollicis longus, Abductor pollicis brevis
–  Adduction:  Abductor pollicis
–  Circumfuction:  Abductors, Flexors, Extensors, and Adductors all working at same time, for the same purpose.
–  Opposition: Opponens pllicis, Flexor pollicis brevis

Metacarpophalangeal Joints  (MCP)

–  These joints are found between the Metacarpal bones (hand) and the Phalanges (Fingers)
–  The joints are considered Condyloid
–  This allows them to allow for movements that include: Flexion, Extension, Adduction, Abduction, and Circumfuction.
–  Flexion of the fingers (excluding thumb) occurs from the Flexor Digitorum Superficialis, Profundus, Lumbricales, and Interossei – that acts on the proximal and distal joints.
–  Flexion of 5th digit or Little finger has an added muscle: Flexor Digiti Minimi Brevis
–  Flexion of the thumb (excluding the other fingers) occurs from the Flexor Pollicus Longus and Flexor Pollicus Brevis
–  Extension of the fingers (excluding thumb) occurs with the Extensor Digitorum Communis, Extensor Indicis Proprius, and Extensor Digiti Minimi Muscle.
–  Extension of the thumb (excluding the other fingers) occurs from the Extensor Pollicus Longus

Interphalangeal Joints:

–  These are the joints in the fingers that allow the fingers to flex towards the palm of the hand.
–  Typically two sets of joints – except in the thumb, which has one set
–  Proximal interphalangeal Joints (PIJ or PIP) is the set of joints in the middle of the finger. Those between the first (proximal) and second (Intermediate) phalanges.
–  Distal Interphalangeal Joints (DIJ or DIP) is the set of joints near the tip of the finger. Those between the second (Intermediate) and third (Distal) phalanges.
–  There is more flexion of the PIP than the DIP
–  The two sets of joints are similar.
–  The only two movements typically allowed, are flexion and extension.
–  Flexion of the fingers (excluding thumb) occurs from the Flexor Digitorum Profundus – that acts on the proximal and distal joints.
–  The Flexor Digitorum Superficialis acts on the proximal joints.
–  Flexion of the thumb (excluding the other fingers) occurs from the Flexor Pollicus Longus
–  Extension of the fingers (excluding thumb) occurs with the Lumbricals and Interossei
–  Extension of the thumb (excluding the other fingers) occurs from the Extensor Pollicus Longus