Reconstruction of the knee extensor mechanism following total knee replacement - Medical Experts

Damage to the extensor mechanism can occur during the surgical implantation of a total knee replacement.

Excessive stress or uncontrolled, jerky movement after surgery can lead to injuries to the extensor mechanism. Typically, the patellar ligament is affected.

Late-onset loosening of the implant or misplacement of the joint inlay can also lead to tissue damage in the extensor mechanism.

This should be distinguished from functional limitations of the extensor mechanism that do not involve mechanical tears of the structures.

Examples include hemorrhages and contusions of the thigh muscles following a tourniquet or neurological microtrauma in the thigh region.

A reflexive or psychogenic reduction in active extension capacity is also possible in cases of temporary postoperative functional disturbances.

Depending on the surgical approach, these should be considered physiological adaptations in the early phase. However, they may also persist over an extended period as part of adaptation disorders.

Complete extension of the knee—particularly active extension against the force of gravity with the leg extended horizontally—is not possible

Pain in the knee area, especially when attempting to actively extend the knee against resistance. Less commonly, pain may also occur during the stabilization phase while walking.

Altered gait or limping to relieve pressure on the affected leg.

Tendency to fall due to a lack of muscular stabilization of the leg at the start of flexion.

Muscle atrophy and, as a result, further loss of strength in the quadriceps muscle

Conservative therapeutic measures are ineffective in cases of complete loss of the extensor mechanism.

To avoid surgery, orthopedic functional orthoses (externally applied braces) of varying designs can partially restore everyday function.

However, patients find these splints uncomfortable for everyday wear, which is why they are not widely used.

• Physical Therapy

In cases of partial functional impairment of the extensor mechanism, targeted exercises can help restore function.

• Electrostimulation

Electrical stimulation can help activate a weakened quadriceps muscle and improve function when anatomical structures are intact.

 Electrical stimulation can be used to strengthen weak muscles after knee surgery @ neotemlpars106 /AdobeStock

• Tendon repair

If the quadriceps tendon is torn, doctors can surgically repair it to restore function.

• Transplantation

In severe cases, a transplant of tendons or muscles from other parts of the body is one option for restoring function. The use of artificial tendon replacement tissue is also possible.

• Implant Revision

If loosening or misplacement of the implants is the cause of the injury, repeat surgery on the prosthesis is necessary.

If surgical restoration of the extensor mechanism is not feasible, fusion of the affected knee joint is performed. However, the ability to bend the knee is reduced.

The choice of treatment option depends on:

• the severity of the injury,
• The patient’s condition, and
• Other individual factors

An accurate diagnosis and appropriate treatment are crucial for restoring the function of the extensor mechanism after total knee replacement.