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Condyloid (ellipsoid) synovial joints between the heads of metacarpals and the bases of proximal phalanges.
Permit movements in two planes — flexion/extension and abduction/adduction.
Head of metacarpal: Convex, broader anteriorly.
Base of proximal phalanx: Concave, fitting the metacarpal head.
Each joint has a separate synovial cavity.
| Ligament | Attachments / Function |
|---|---|
| Palmar (volar) ligament / plate | Thick fibrocartilaginous plate attached firmly to base of proximal phalanx, loosely to metacarpal head → prevents hyperextension. |
| Collateral ligaments (proper + accessory) | From sides of metacarpal heads → base of proximal phalanx and volar plate → check abduction during flexion. |
| Deep transverse metacarpal ligaments | Connect volar plates of 2nd–5th MCP joints → maintain transverse arch of palm. |
Surrounds each joint; attached to margins of articular surfaces.
Lined by synovial membrane.
| Movement | Range / Plane | Muscles Responsible |
|---|---|---|
| Flexion | 0–90° | FDS, FDP, lumbricals, interossei |
| Extension | Up to 45° | EDC, EIP, EDM |
| Abduction | Fingers move away from midline (middle finger) | Dorsal interossei |
| Adduction | Toward midline | Palmar interossei |
| Circumduction | Composite | Sequential activation of above muscles |
Passes through head of metacarpal; middle finger acts as axis of reference (no adduction possible for it).
Collateral and palmar ligaments.
Interosseous muscles tonus.
Integrity of deep transverse metacarpal ligaments.
Digital branches of median and ulnar nerves (Hilton’s law).
MCP dislocation: Often dorsal; volar plate may trap metacarpal head → irreducible without surgery.
Rheumatoid arthritis: MCP joints show swelling, ulnar deviation, and boutonnière deformity.
Knuckle pads: Fibrotic thickening over MCP joints from repetitive trauma.
Hinge-type synovial joints.
Allow movement in one plane (flexion–extension only).
Head of proximal phalanx: Pulley-shaped, with two condyles.
Base of distal phalanx: Concave with two shallow facets.
Covered by hyaline cartilage and enclosed by a capsule.
| Ligament | Function |
|---|---|
| Palmar (volar) ligament / plate | Prevents hyperextension. |
| Collateral ligaments | Maintain lateral stability during flexion. |
(No deep transverse ligaments here.)
Proximal Interphalangeal (PIP) – between proximal & middle phalanges.
Distal Interphalangeal (DIP) – between middle & distal phalanges.
(Thumb has only one IP joint.)
| Movement | Range (°) | Muscles Responsible |
|---|---|---|
| Flexion | Up to 100–120° (PIP), 80–90° (DIP) | FDS (PIP), FDP (DIP) |
| Extension | Limited (~30°) | EDC, EPL, lumbricals, interossei |
Transverse axis through heads of phalanges.
Strong collateral ligaments.
Volar plates.
Tendon expansion of extensor mechanism (dorsal digital expansion).
Digital branches of median and ulnar nerves.
Rupture or avulsion of extensor tendon at DIP joint → finger tip droops.
Common in ball sports injuries.
Hyperextension of PIP with flexion of DIP joint → seen in rheumatoid arthritis due to imbalance of flexor/extensor forces.
Flexion of PIP and hyperextension of DIP joint → rupture of central slip of extensor tendon.
Progressive fibrosis of palmar fascia → flexion deformity at MCP and PIP joints (especially ring and little fingers).
Thickening of flexor tendon sheath → tendon “snaps” during flexion or extension.
Follows fractures or tendon adhesions; early physiotherapy essential.
MCP joints allow fine finger spread and precision positioning.
IP joints ensure powerful grasp and release.
Coordination of both ensures the prehensile function of hand — grip, pinch, and manipulation.
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