Buckling after Total Knee Replacement

Knee replacement surgeries are highly successful surgeries aimed to help relieve knee pain and associated disability. However, some patients may not have optimal results and may complain of wobbling or buckling of the knee after the surgery.

The buckling of the knee after the replacement is instability that may result from preoperative, operative, or postoperative factors. Frequently, instability after total knee replacement requires revision surgery to address the cause of instability and prevent reoccurrence.

Knee replacement surgery consists of replacing the diseased ends of the bones forming the knee joint with metal and plastic prosthetic parts. During the surgery, the surgeon makes bone cuts using templates at specific angles and directions to ensure a balanced artificial knee joint.

Balancing of the knee ensures that there is no excess pressure or tension on the tissues on the front, back, and sides. Additionally, with the balancing of the knee, the deformity is usually corrected, and the body weight is evenly distributed on both sides of the knee joint.

Intraoperative fluoroscopic image showing modular revision knee replacement.

What is Buckling After Total Knee Replacement?

Imagine you’re walking, and suddenly your knee gives out, causing you to stumble or fall. That’s what buckling feels like. Buckling after TKR refers to a sudden and unexpected loss of strength or stability in the knee joint, leading to a feeling of instability or giving way.

Causes of Buckling After Total Knee Replacement:

Several factors can contribute to buckling after TKR. One major cause is weakness or imbalance in the muscles around the knee. During TKR surgery, some muscles and tissues are inevitably disturbed, which can affect their strength and coordination. Additionally, changes in joint mechanics or alignment after surgery may also contribute to instability.

Another significant factor is proprioception, which is the body’s ability to sense its position in space. Proprioception can be impaired following TKR due to changes in joint anatomy and nerve function, making it harder for the brain to accurately perceive the position and movement of the knee.

Furthermore, complications such as infection, implant loosening, or improper surgical technique can also increase the risk of buckling after TKR. These issues compromise the integrity of the joint, leading to instability and potentially buckling episodes.

Impact on Quality of Life

Buckling after TKR can have a profound impact on a person’s quality of life. It can lead to fear of falling, reduced mobility, and decreased participation in daily activities and recreational pursuits. Additionally, repeated buckling episodes may cause further damage to the knee joint and surrounding structures, exacerbating pain and functional limitations.

The instability is an early sign of failure of knee replacement. The patients may often complain of knee pain with wobbling or buckling of the knee joint. The risk of instability is greater in patients with connective tissue and inflammatory diseases such as rheumatoid arthritis or diabetes mellitus, etc.

Patients requiring knee replacement surgery often have a preoperative knock knee or bow leg deformity. Patients with bow leg deformity have excessive laxity of tissues on the outer side of the knee while the tissues on the inner side are tight or contracted. During the surgery, the surgeon tries to lengthen the contracted tissues by releasing them from the inner side of the knee.

Similarly, in patients with a knock knee deformity who may need a joint replacement surgery, the tissues on the outer side of the knee are contracted and tight. In order to correct the deformity, the surgeon works to release the tight tissues on the outer side of the knee. Excessive release of tissues on either the inner or the outer side of the knee during replacement surgery may lead to joint laxity and instability.

Patients that may require revision knee replacement due to any reason such as infection, loosening, implant malposition, implant breakage, etc. are also at an increased risk of instability following revision surgery.

After the primary knee replacement surgery, the tissues around the knee joint may often become thick and fibrous. The thickening of the tissues may often make balancing the knee difficult during revision surgery leading to instability. Knee instability after replacement surgery is usually divided/classified depending upon the direction of instability.

Varus-valgus instability (side to side)

The patients experience instability in the side to side direction which may occur as a result of excessive cutting of the lower end of the thigh bone (femur), or inadequate correction of knock knee/bow-legs deformity during the surgery.

Flexion instability

The front-back instability may occur as a result of over resection of the back surface of the femur condyle, using a small femur implant, or excessive slope of the tibial implant. In the case of cruciate-retaining (CR) knee replacement, anterior-posterior instability may result from insufficiency of the posterior cruciate ligament.

Mid flexion instability

The instability becomes evident in the form of malrotation on bending the knee from 45 degrees to 90 degrees. A number of different implants and surgical factors may contribute towards mid-flexion instability.

Genu recurvatum

In some patients there may be instability in the form of excessive extension of the leg. The leg overshoots the normal straight alignment of the knee and may become fixed in overextension position as a result of contracture of the iliotibial band. The genu recurvatum deformity may be associated with diseases such as rheumatoid arthritis, Charcot disease, and poliomyelitis.

Intraoperative image of knee replacement surgery.

Global instability

The instability in multiple planes after knee replacement surgery is known as global instability. Global instability often results from severe bone loss as a result of multiple surgeries.

Diagnosis

The diagnosis of instability after a knee replacement is made by the physician based on the history of the patient including the type of surgery and any comorbid conditions. An x-ray, CT scan or MRI may be done to look for implant positioning and the surrounding bone. Blood investigations may be done in case an infection is suspected.

Management

The treatment of knee instability after knee replacement depends upon the degree of instability and the type of instability. The management is usually surgical and bracing may be done in a small subset of patients. The revision surgery may utilize special implants to decrease instability such as hinged implants or implants with rotating platforms.

Treatment Options

Treatment for buckling after TKR depends on the underlying cause and severity of symptoms. In many cases, conservative measures such as physical therapy, strengthening exercises, and gait training can help improve muscle strength and coordination, thereby reducing episodes of buckling.

Orthotic devices such as knee braces or custom orthotics may also provide additional support and stability for individuals experiencing buckling after TKR. These devices help offload stress from the knee joint and improve alignment during weight-bearing activities.

In some cases, surgical intervention may be necessary to address persistent instability or correct underlying issues contributing to buckling. This may involve revision TKR surgery to replace or adjust the existing implants, repair damaged soft tissues, or realign the joint to improve stability and function.

Prevention

While it’s not always possible to prevent buckling after TKR entirely, there are steps individuals can take to minimize their risk. This includes following post-operative rehabilitation protocols prescribed by their healthcare team, maintaining a healthy weight to reduce stress on the knee joint, and avoiding high-impact activities that may increase the risk of injury or implant failure.

Conclusion

Buckling after TKR can be a challenging and frustrating complication for patients to navigate. However, with proper diagnosis and treatment, many individuals can experience significant improvement in symptoms and regain confidence in their ability to move and function without fear of instability. By working closely with their healthcare team and adhering to recommended treatment plans, individuals can take proactive steps to manage buckling after TKR and enjoy a better quality of life.

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