Knee Replacement “Clicking”
Following knee replacement surgery, patients sometimes report hearing clicks or a clicking sound during certain activities or at a certain point or points during their gait cycle. In most cases, this sound is believed to be benign and is not associated with pain or other adverse consequences.
So what causes this clicking?
To answer this question, it is helpful to understand a little bit about the nature of total knee replacement. In knee replacement, the ends of the bones that make up the knee joint are “resurfaced” with metal and plastic components. The surgeon uses specialized instrumentation and surgical technique to properly align the implants to the bones and the bones to one another.
This alignment is not straightforward because in the replaced knee joint, as in the normal knee, the bones are not “mechanically interconnected”; rather the joint is constrained by the remaining soft tissue (ligaments, muscles/tendons) and the conformity of the implant components. During the knee replacement operation, the surgeon works to optimize range of motion and joint stability through proper alignment and sizing of the implant.
The resulting tension in the replaced joint can, therefore, vary slightly from patient to patient and can be different within the range of motion of a single patient. That is, some patients may have “tighter” knees or “looser” knees or a single knee can be “tight” in flexion, but “loose” in extension and vice versa, but in general, some degree of laxity is desirable to allow for adequate motion.
Because there is almost always some laxity in a replaced knee, clicking can sometimes be heard as a result of contact between the metal and plastic components during activity. Often it is heard during a transition from low or non-weight bearing to weight bearing. For example, a patient may hear the click while walking as the leg comes out of swing phase and makes contact at heal strike. For the most part, the clicking is usually not associated with any adverse conditions.