Painful knee prosthesis (revision)
During a revision, the individual components of the previously implanted prosthesis are replaced. This is also referred to as replacing the artificial knee joint.
The service life of the knee prosthesis depends on various influencing factors such as age, weight, bone condition and physical activity. In addition to the aforementioned natural signs of wear and tear, premature loosening of the knee prosthesis can also be a reason for replacing a knee prosthesis. Such loosening can lead to pain and a feeling of instability in the knee. Complaints such as swelling or restricted movement are also possible.
The position of the knee prosthesis is checked by means of an X-ray examination. In addition, joint function, ligament stability and muscle function are checked in a detailed clinical examination. If necessary, a check is also carried out to determine whether there is an infection caused by bacteria. The aim of this procedure is to eliminate the existing symptoms and restore full weight-bearing capacity and mobility. Unfortunately, conservative methods are not available, so a replacement operation is the only solution. Such an operation should not be postponed under any circumstances, as otherwise further bone loss and fractures are possible.
Frequent complaints
Pain
According to specialist literature, around 30 per cent of patients with artificial knee joints are dissatisfied with the result and complain of knee pain, restricted movement and insecurity. These complaints can occur shortly after the operation or at a later stage. For most patients, pain is the main symptom. This can occur at rest, during exertion or during movement. The pain can come on suddenly or become increasingly severe over time. The type of pain can also vary greatly: from burning, pulling, stabbing, electrifying to dull. The pain is accompanied by joint effusion, which restricts knee mobility. The pain can be felt inside or outside the knee joint.
Instability
Another common problem is unsteadiness when walking with an artificial joint or buckling. This instability of the knee joint can lead to an increased risk of falling. For certain patients, the restriction of movement of the artificial knee joint is the main issue. This can be so severe that patients are very restricted in their everyday life, e.g. when walking up and down stairs.
What are the reasons for a painful knee prosthesis?
The causes of a painful knee prosthesis are very varied and can be due to the operation, the knee prosthesis or the patient themselves. For example, causes that promote discomfort after an artificial knee joint include excessive expectations, overuse, formation of scar tissue, lax collateral ligaments, infection, loosening of the prosthesis, increase in osteoporosis, allergy, falls, overreaction of skin nerves (M. Sudeck's disease, complex regional pain syndrome [CRPS]), increase in osteoarthritis behind the kneecap, wear and tear, misalignment of the prosthesis in relation to the longitudinal axis, rotation or tilting, knee prosthesis too large, knee joint prosthesis not optimally positioned with corresponding overhang, tilting of the kneecap, jumping out or non-optimal guidance of the kneecap, insufficiently balanced collateral ligaments, etc.
How are the causes clarified?
If a patient with a painful knee prosthesis comes for an assessment, the questioning and examination are very important. This is followed by normal X-ray images of the knee or individual specialised examinations such as Whole-leg x-ray (visualisation of the leg axis), SPECT-CT (combination of scintigraphy and computer tomography to anatomically visualise the current bone activity), rotational CT (visualisation of the rotation of the knee prosthesis) and allergy investigations. The knee joint is also examined for redness, overheating, swelling or joint effusion. This is followed by testing the mobility and stability of the knee joint. The movement of the kneecap is then tested. Are any noises audible when the knee joint moves and does anything pop in the joint? Can pain be provoked with certain grips? How is the gait?
How are the complaints treated?
Depending on the cause of the painful knee prosthesis, different therapies are recommended. These start with conservative measures such as physiotherapy, insoles and medication. If these are ineffective or have already been exhausted, surgery is recommended to correct the problem. Depending on the diagnosis, joint-preserving surgery, partial replacement or replacement of the prosthesis may be considered:
Joint-preserving surgery
- Removal of painful scarring or free joint bodies either openly or via arthroscopy (arthroscopy)
- Irrigation of the joint and collection of tissue samples for microbiological examination to rule out an infection
- Reconstruction of the joint capsule
- MPFL reconstruction: This is used to restore the stable inner guiding ligament of the kneecap with the body's own tendon.
Partial replacement of the artificial joint
- Replacement of the back surface of the kneecap (retropatellar replacement)
- Replacement of the inlay (plastic disc)
New artificial knee joint
- In certain cases, the same prosthesis model of the artificial knee joint can be used.
- If the bone quality is too weak (advanced osteoporosis), the bone loss is too great or the collateral ligaments are too weak, the knee joint can be stabilised with a guided revision prosthesis (see chapter "Revision prosthesis").
- If an allergy (metal, cement) is detected, the artificial knee joint should be replaced with a special allergy prosthesis (see chapter "Allergy prosthesis").
- In the case of a chronic infection, the artificial knee joint is removed and replaced with a dynamic cement spacer. This is followed by targeted antibiotic therapy for six to nine weeks, depending on the germ. If the inflammation values are within the normal range two weeks after discontinuation of the antibiotics and the knee joint is clinically free of irritation, a new artificial knee joint can be inserted (see chapter "Knee prosthesis" or "Revision prosthesis")
How does the follow-up treatment work?
The appropriate follow-up treatment depends on which therapy is carried out. As a rule, once the artificial knee joint has been cemented into place, the knee can be fully loaded and moved immediately. Immobilisation is recommended for approx. six weeks to protect the soft tissue.
Physical measures to relieve swelling and strengthen and stretch the thigh muscles are also important after the operation. If an infection is detected, several weeks of antibiotic therapy tailored to the infection will follow.
Only with experienced specialists
Problems with artificial knee joints require a complex analysis and a great deal of experience. Revision surgery is an area in itself, which is why you should only put yourself in the hands of an experienced doctor.
Book a consultation appointment
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Dr Andreas L. Oberholzer is a recognised expert in knee problems and has extensive experience in the field of artificial knee joints.
Book your appointment directly online here or call us on +41 44 388 16 16. You are also welcome to come to us for a second opinion.
PD Dr Andreas L. Oberholzer
FMH specialist in orthopaedics and trauma surgery. Areas of specialisation: Knee, hip and foot surgery.