Normal Motion After Knee ReplacementNormal motion after knee replacement is usually defined as the ability to get within about 5 degrees of a straight knee, and the ability to bend the knee back to 90 degrees. Most activities can be performed with this motion, but surgeons strive to have knee replacements with motion from 0 degrees (fully straight) to 110 degrees or more. Often full motion is not achieved until 3 to 6 months from the time of surgery.
After knee replacement surgery, it is important to work with a physical therapist in order to achieve maximal range of motion. Some surgeons will recommend the use of a machine to bend the knee, called a CPM, despite the lack of evidence to support the use of these machines. Optimal motion of the replaced knee can be achieved with a combination of stretches, exercises, and gradual resumption of normal activities.
When Knee Replacements Are StiffIn some people, knee motion can be difficult to regain after surgery. Lack or normal motion after knee replacement can be due to one of several causes, or a combination of causes:
- Inadequate Pain Control
Pain control after joint replacement is usually a manageable problem, but in some people this can be quite difficult. Some patients find the side effects of pain medication intolerable, but a lack of adequate pain control can lead to difficulty working on motion of the newly replaced joint. It is important to work with your doctor to develop a pain treatment plan that works for you.
- Poor Motion Before Surgery
Your motion before surgery can be used to predict your motion after surgery. Patients with stiffness before their surgical procedure are more likely to have stiffness after surgery.
- Abundant Scar Formation
Some people seem to make scar tissue more abundantly than others, and there are some situations where scar formation is more abundant. Patients who have undergone prior joint surgery, or are having revision knee replacement, are more likely to have stiffness after surgery.
- Malpositioning of the Replacement Implants
Surgeons make an effort to "balance" the knee at the time of surgery. This means finding the proper size and alignment of the knee replacement so that the knee joint is not too tight, and not too loose, and so this balancing is the same with the knee straight and bent. This is precisely why a knee replacement is a difficult procedure, and the art of perfecting this takes many years. Errors in positioning of the implants at the time of surgery may not be apparent on the operating table, and can cause difficulty bending or straightening the knee.
- Other Surgical Complications
Complications of surgery often lead to other problems. Patients who experience joint replacement infections, complex regional pain syndrome, or other complications, have a higher chance of developing stiffness.
Treatment of Knee Stiffness After ReplacementTreatment of stiffness after knee replacement depends on the time since surgery, and the cause of the stiffness. The usual treatments of stiffness are:
- Aggressive Physical Therapy
Physical therapy is a useful treatment for a stiff knee, especially within the first three months after knee replacement. Physical therapy can also be considered after this time, but the results are not as good as early physical therapy. A new type of splint, called a dynamic splint, has also shown some encouraging results when used in conjunction with physical therapy.
- Manipulation Under Anesthesia
A manipulation is a procedure where no incisions are made. The patient is given anesthesia, usually through an IV, and while sleeping, your surgeon forcibly moves the knee to break up scar tissue. This procedure is most beneficial in the 6 to 12 weeks after surgery. The primary concern with a manipulation is that there is a possibility the bone can break around the implant if forced too hard. This is most concerning in people with osteoporosis or when the manipulation is performed more than a year after replacement.
- Surgical Removal of Scar Tissue
Surgical removal of scar tissue after knee replacement is seldom performed, but may be helpful in some rare circumstances. The results of removing scar tissue have not been particularly good at improving motion, and therefore, usually other treatments are considered first.
- Revision Knee Replacement
When the above treatments fail, or if the knee replacement parts are malpositioned, it may be necessary to remove the implanted knee and replace this with a new knee replacement. The bone cuts and the size of the new replacement can be modified to help allow for better knee motion.
Bong MR, and Di Cesare PE. "Stiffness After Total Knee Arthroplasty" J. Am. Acad. Ortho. Surg., May/June 2004; 12: 164 - 171.