Pain after Knee Replacement
During the knee replacement surgery, the diseased ends of the knee joint are removed. Prosthetic metal parts are placed at the bone ends that reduplicate the function of the knee joint. A plastic polyethylene insert is placed in between the two opposing metal surfaces.
General pain in the knee after replacement surgery is part of the recovery process. The pain may be associated with swelling and generally goes down in the initial 2-3 weeks. The pain is typically managed with medications such as non steroidal anti-inflammatory medications or short term opioid medications. The swelling is generally managed using an ice pack.
While the general knee pain slowly goes away in the initial few days, some patients may need oral pain medications for several weeks after the surgery. Physical therapy and home exercises help to decrease the pain.
For diagnosis of the cause of the pain, the physician will note the characteristics of the knee pain. The quality, location, onset, radiation, relieving and aggravating factors all help the physician to find the cause is pain. The physician conducts a thorough physical examination and may request radiological studies in the form of an X-ray, CT scan or an MRI. Blood investigations may be done to look for signs of infection.
The cause of pain after knee replacement may be due to a variety of reasons.
- Sudden sharp pain after a pain free period may point towards a fracture of the bone surrounding the implant. The fracture may involve the lower end of thigh bone, the upper end of shin bone or the knee cap.
While a minor fracture is generally managed with non surgical casting/splint, the majority of the periprosthetic fractures require surgical management. They may either be fixed with plates or rods, or may require implantation of a newer modified implant.
- Pain occurring years after the surgery may point towards aseptic loosening. The loosening may occur as a result of wear and tear of the implant. The patient may often complain of pain only on bearing weight. The activity related pain is often relieved on rest. The management is surgical in the form of revision knee replacement.
- Pain associated with giving away sensation may be associated with instability. The instability may result in rapid wear of the polyethylene insert. The patients may often complain of pain and instability in specific ranges of motion. The management involves revision knee surgery.
- Pain associated with weakness of the knee may occur as a result of rupture of the extensor mechanism. The extensor mechanism depends upon the integrity of the thigh bone, quadriceps muscle, quadriceps tendon, kneecap and the patellar tendon.
Any disruption of the mechanism results in inability to straighten the leg or weakness. Treatment may be non surgical in partial rupture and surgical in complete.
- Pain associated with a dislocation/subluxation of the knee cap may occur as a result of maltracking of the kneecap. The kneecap glides smoothly in the groove formed by the prosthetic femoral component.
If the kneecap doesn’t glide in the tract, it may result in pain often associated with the feeling of the kneecap moving out of place on bending and straightening the knee. The management is surgical.
- Pain associated with catching the kneecap occurs as a result of patellar clunk syndrome. The pain usually occurs a year after the surgery and patients may complain of something catching in their knee upon bending and straightening the knee. The management is surgical and may be done with the help of an arthroscope.
- Abnormal bone formation in the knee after the surgery known as heterotrophic ossification may also lead to postoperative pain. The pain is often associated with stiffness of the knee joint.
- Pain associated with swelling, redness and fever is usually associated with infection of the prosthetic joint. A serious complication that usually requires a revision surgery. The revision surgery may be a single step surgery or a two step surgery.
- Complex regional pain syndrome is a condition that may cause severe pain along with paresthesia. The pain may be associated with changes in skin color and temperature. Patients often require multi-modal management of the symptoms.
- Nerve injuries during the surgery may result in persistent pain in the knee. The pain may or may not improve over time. A pinched nerve in the lower back may also present as pain in the knee joint. Rarely, a hip pathology may present as a referred pain to the knee joint.
- In some cases, the cause of pain after knee surgery may remain elusive despite multiple evaluations.
Despite the rare complications, knee replacement remains one of the most successful surgeries in modern medicine. The knee replacement surgery is boon to the patients who are disabled with pain and restriction of activity due to arthritis. Pain after knee surgery usually gets better in a few weeks and your surgeon may help diagnose and treat any pain not getting better or worsening after the initial postoperative period.