Ellipsoidal (Condyloid) Joints

1. Overview

An ellipsoidal joint, also known as a condyloid joint, is a type of synovial joint that permits movement in two planes: flexion–extension and abduction–adduction. These biaxial joints have an oval-shaped condyle of one bone fitting into the elliptical cavity of another, allowing angular but not rotational movement. Ellipsoidal joints are essential for precise, controlled motion and are found in areas requiring coordinated mobility and stability.

2. Location

Ellipsoidal joints are present in several key areas of the body:

• Wrist joint (radiocarpal joint): Between the distal radius and the scaphoid and lunate carpal bones.

• Metacarpophalangeal joints (MCPs): Between the heads of metacarpal bones and bases of proximal phalanges in the fingers (knuckle joints).

• Atlanto-occipital joint: Between the occipital condyles of the skull and the superior facets of the atlas (C1 vertebra).

• Metatarsophalangeal joints (MTPs): Similar joints in the toes.

3. Structure

Ellipsoidal joints are structured for complex movement within a confined range:

• Articular surfaces: One surface is an oval convex condyle, and the other is a reciprocally shaped concave surface.

• Joint capsule: Encloses the joint and is lined by a synovial membrane that secretes synovial fluid.

• Synovial fluid: Lubricates the joint, reduces friction, and nourishes articular cartilage.

• Ligaments: Surround and stabilize the joint, preventing excessive or abnormal movement.

• Articular cartilage: Covers the joint surfaces, allowing smooth, low-friction interaction between bones.

4. Function

Ellipsoidal joints allow a range of controlled, angular motions:

• Flexion and extension: Movement in the sagittal plane, such as bending and straightening fingers.

• Abduction and adduction: Movement in the coronal plane, such as spreading fingers apart or bringing them together.

• Circumduction: A circular, conical motion combining flexion, extension, abduction, and adduction (but no axial rotation).

5. Physiological role(s)

Ellipsoidal joints play crucial roles in fine and gross motor function:

• Manual dexterity: MCP joints are key to grasping, pinching, and manipulating objects with precision.

• Postural alignment: Atlanto-occipital joint helps support head posture and balance.

• Locomotion support: MTP joints contribute to propulsion and toe-off during walking and running.

• Articulation balance: These joints enable complex joint interplay without compromising stability.

6. Clinical Significance

Several conditions can affect ellipsoidal joints and impair their function:

• Osteoarthritis:

  • Degeneration of articular cartilage in MCP or wrist joints causes stiffness, pain, and loss of function.

• Rheumatoid arthritis:

  • Commonly affects MCP joints with joint swelling, deformity (e.g., ulnar drift), and inflammation.

• Atlanto-occipital dislocation:

  • A rare but life-threatening injury where the skull becomes dislodged from the spine, often due to trauma.

• Joint contracture or stiffness:

  • Prolonged immobility or scarring may limit movement at ellipsoidal joints, particularly in the fingers.

• Joint injections or aspiration:

  • Inflamed or swollen ellipsoidal joints, especially the wrist, may require corticosteroid injections or fluid removal for relief.