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Joint Capsule of the MCP/MP
- Highly specialized
- It encompasses the joint space and attaches to the sides of both articular surfaces
- Volar side forms a strong plate of fibrocartilage called the volar plate (VP)
- The medial and lateral edges of the VP act as an attachment for the tendon sheaths and A1 pulley
- The VP gives stability of the tendons and prevents bowstringing of the tendons allowing for better biomechanical function of the tendons
- The VP can slide proximally with flexion because it is thin and able to fold proximally, but distally it is thick and rigid
- The volar plate is slack in extension and taut in hyperextension
The collateral ligament (CL) is:
- Triangular
- Has 2 parts (accessory and proper/cord are the two parts)
- Fibers of the CL extend more distally and form the strongest part of the CL
- Generally speaking the CL is loose in extension allowing MCP abduction and adduction
- Proper are taut in Flexion and slack in extension while the accessory ligaments are located more volar so they are lax in flexion and taut in extension
- As proximal phalanx is flexed the proper CL is taut in full flexion due to shape of MC head. Tightness prevents full abduction and adduction.
- VP also serves as an attachment and accessory (or the fan part of the CL) and stabilizes long finger flexors.
The proper collateral ligament (CL) is taught in full extension hence why it is important to always place MPs in full extension after injury to recover. True or False
FALSE - the Proper CL at MCP in full extension are Loose and in flexion proper CL is taut. Orthotics and positioning should place the MCP in flexion to put the CL on tension and prevent shortening of this important ligament.
