Experiencing clicking sounds in the knee after a total knee replacement can be a noticeable sensation. While it might cause concern, this phenomenon is often a normal part of post-surgical healing and adaptation. This article aims to clarify the common causes behind these noises and identify situations where medical attention may be beneficial.
Understanding Your Replaced Knee
A total knee replacement involves surgically removing damaged bone and cartilage from the knee joint and replacing them with artificial components. This sophisticated implant typically consists of a femoral component, which caps the end of the thigh bone, and a tibial component, which covers the top of the shin bone. Between these two metal parts, a durable plastic spacer, often made of polyethylene, is inserted to function as the new cartilage, allowing for smooth movement. An optional patellar component, placed on the kneecap, may also be included. These materials, metal alloys and plastic, are non-biological and interact differently from natural bone and cartilage.
Common Reasons for Clicking
The most frequent reason for clicking sounds is the direct interaction between the artificial components themselves. As the metal femoral component moves against the polyethylene spacer, particularly during bending and straightening, audible sounds can occur because these hard materials behave differently from natural cartilage. Initially, swelling in the joint might mask these sounds, but as swelling reduces, the components have more freedom to move and create noise.
Another cause involves the soft tissues surrounding the knee, such as tendons, ligaments, or newly formed scar tissue. These tissues may occasionally rub or catch on the implant during movement, resulting in a clicking or popping sound. Patellar clunk syndrome can occur when a fibrous nodule forms and catches on the femoral component. As the body adjusts and tissues adapt, these sounds often diminish over time.
Sometimes, clicking can be attributed to the formation and collapse of gas bubbles within the synovial fluid of the joint, a phenomenon known as cavitation. This is similar to the sound produced when cracking knuckles and is typically harmless. Early after surgery, residual fluid within the joint can also contribute to these mechanical sensations, which usually resolve as the fluid is reabsorbed.
Less common factors like minor malalignment of implant components can alter knee mechanics, leading to clicking. Additionally, component loosening or wear of the plastic spacer could contribute to clicking, though these are typically accompanied by other symptoms. Many of these mechanical causes are considered benign, especially if the clicking occurs in isolation without other issues.
When to Consult Your Doctor
While isolated clicking after knee replacement is often normal and not a cause for concern, certain accompanying symptoms warrant a medical evaluation. It is advisable to consult a healthcare professional if the clicking is associated with new or worsening pain in the knee. This pain could range from mild discomfort to severe, persistent pain that interferes with daily activities.
Other indicators that suggest a need for medical review include swelling, warmth, or redness around the knee, which could signal inflammation or potential infection. Instability, a feeling of the knee “giving way,” or the knee locking up or catching are also important symptoms to report. Inability to bear weight on the affected leg or the presence of a fever alongside clicking should prompt immediate medical attention.
A sudden change in the nature of the clicking, such as it becoming louder, more frequent, or evolving into a grinding sensation, should be discussed with your surgeon. If the clicking consistently impacts your daily activities or causes distress, seeking professional advice can provide reassurance and address any underlying issues.