Drop-Lock Joint
A mechanical orthotic joint mechanism featuring a spring-loaded ring that drops to lock the joint in extension and can be manually lifted to allow flexion.
Full Definition
A drop-lock (or ring-lock) joint is a commonly used mechanical joint in KAFOs and HKAFOs, consisting of a proximal and distal upright connected by a hinge with a sliding or rotating locking ring. When the knee or hip reaches full extension, a spring-loaded ring drops into a groove, locking the joint and preventing flexion during stance. The user or carer manually raises the ring to unlock the joint for sitting. Editors will encounter this term in device prescriptions, clinical notes, and insurance justifications. It must not be confused with 'bail lock' (also called a Swiss lock or pawl lock), which allows unlocking by pressing the back of the knee. Precision in naming joint mechanisms is critical for correct device fabrication.
Usage
Usage note: Hyphenate as 'drop-lock joint'; distinguish clearly from 'bail lock' in all prescriptions and clinical records.
In Context
- "The KAFO was fitted with bilateral drop-lock joints to stabilise the knee during ambulation, with unlocking required for seated activities." — Orthotic device prescription
- "Verify whether 'drop-lock' or 'bail lock' is intended; both are ring-style mechanisms but differ in the unlocking method." — Editorial query on orthotic work order