Abstract
The etiology of the flexion contracture is related to recurrent effusions present in a knee with end-stage degenerative joint disease secondary to the associated inflammatory process. These recurrent effusions cause increased pressure in the knee causing pain and discomfort. Patients will always seek a position of comfort, which is slight flexion. Flexion decreases the painful stimulus by reducing pressure in the knee and relaxing the posterior capsule. Unfortunately, this self-perpetuating process leads to a greater degree of contracture as the disease progresses. Furthermore, patients rarely maintain the knee in full extension. Even during the gait cycle the knee is slightly flexed. As their disease progresses, patients limit their ambulation and are more frequently in a seated position. Patients often report sleeping with a pillow under their knee or in the fetal position. All of these activities increase flexion contracture deformity. Patients with excessive deformity >40 degrees should be counseled regarding procedural complexity and that increasing constraint may be required. Patients are seen preoperatively by a physical therapist and given a pre-arthroplasty conditioning program. Patients with excessive flexion contracture are specifically instructed on stretching techniques, as well as quadriceps rehabilitation exercises.
The focus in the postoperative physiotherapy rehabilitation program continues toward the goal of full extension. Patients are instructed in appropriate stretching regimes. Patients are immobilised for the first 24 hours in full extension with plaster splints, such as with a modified Robert Jones dressing. This dressing is removed on postoperative day one. The patient is then placed in a knee immobiliser and instructed to wear it at bed rest, during ambulation and in the evening, only removing for ROM exercises. In cases of severe flexion deformity >30 degrees, patients are maintained in full extension for 3–4 weeks until ROM is begun. Patients are encouraged to use a knee immobiliser for at least the first 6 weeks postoperatively.
Treating patients with flexion contracture involves a combination of bone resection and soft tissue balance. One must make every effort to preserve both the femoral and tibial joint line. In flexion contracture the common error is to begin by resecting additional distal femur, which may result in joint line elevation and mid-flexion instability. The distal femoral resection should remove that amount of bone being replaced with metal. Attention should be directed at careful and meticulous balance of the soft tissues and release of the contracted posterior capsule with re-establishment of the posterior recess, which will correct the majority of flexion contractures.
Inability to achieve ROM after TKA represents a frustrating complication for both patient and surgeon. Non-operative treatments for the stiff TKA include shoe lift in contralateral limb, stationery bicycle with elevated seat position, extension bracing, topical application of hand-held instruments to areas of soft tissue-dysfunction by a trained physical therapist over several outpatient sessions, and use of a low load stretch device. Manipulation under anesthesia is indicated in patients after TKA having less than 90 degrees ROM after 6 weeks, with no progression or regression in ROM. Other operative treatments range from a downsizing exchange of the polyethylene bearing to revision with a constrained device and low-dose irradiation in cases of severe arthrofibrosis.
