Major joint replacement is one of the success stories of the late twentieth century, providing the greatest changes in quality of life measurements of all medical treatments or operations. Total knee replacement has now developed from a less predictable operation to a routine procedure with good long-term results for severely osteoarthritic joints. Populations in developed countries are rapidly getting older and total knee replacement is set to overtake total hip replacement as the most performed joint replacement.
Medical technology developed in the late twentieth century to the stage that joint replacement has become a common and predictable treatment for severely arthritic joints, proving to give the highest quality of life of all medical interventions. Total knee replacement is now a predictable and very successful intervention with good ten year results and beyond. Knee replacement is becoming a more popular operation than hip replacement and as western populations get older the demand will increase.
Metal and plastic components are inserted to replace the degenerative joint surfaces of the knee. In knee replacement these consist of four items:
* Femoral component. This is a steel alloy and replaces the arthritic end of the thigh bone.
* The metal tibial insert to replace the tibial surfaces, the lower half of the knee.
* The plastic insert, made of ultra high density polyethylene, is placed between the femoral and tibial inserts.
* A plastic button which fixes on to the posterior surface of the patella, without which some patients continue to complain of anterior knee pain after replacement.
Cement is used as a grout to fix the components but a precise and tight fit is more important in keeping them in place.
Once the operation has been completed the physiotherapist must treat the consequences of the operation to ensure a successful outcome for the patient. Surgery causes pain, swelling, inflammation and muscle weakness and much of the early physiotherapy is targeted towards this. Initially the physio can use a Cryocuff, a refillable pressure cuff fitted closely to the knee, to reduce the swelling and to provide cold therapy over an extended period, reducing the pain and facilitating muscle action. Taking the painkillers regularly and static quadriceps exercises are encouraged hourly to re-establish muscular knee control and gentle knee flexion exercises to get the knee range of movement going.
Next the physiotherapist assesses the patient for suitability for their first mobilisation, checking the operation note, the patient’s medical observations and the condition of the legs themselves. The operated knee has to have enough stability to safely weight bear, as an epidural can cause profound loss of muscle power and prevent safe mobilisation until the drugs wear off. The patient is mobilised into standing by the physio with an assistant and encouraged to walk a small distance with elbow crutches or a Zimmer frame for more elderly persons. Operative protocol usually encourages normal weight bearing through the new knee as this helps restore normal patterns of muscular activity and improves circulation.
Outpatient physiotherapy aims to restore normal muscle power and function, joint range of motion and regain functional abilities. Initial exercises include knee hangs for full passive extension (very important for normal knee function), inner range quadriceps to restore active extension to full range and knee flexion to increase range. Resisted flexion over the edge of a bed helps the quadriceps relax by reciprocal inhibition and allows increases in flexion range. This can be manually resisted by a physio or performed against a spring or Theraband. Massage to the scar area is also useful to mobilise the scar and free up the tissues.
Further rehabilitation is more likely to take place in the gym, concentrating on functional activities such as moving from sitting to standing and step ups and strengthening work with Theraband and the gymnastic ball. Work on range of motion will continue using resisted exercises and static bicycling and patients can usefully work on proprioception using the wobble board and other balance related activities. Proprioception is the normal ability of a joint to sense its position in space and this is very important for normal activity and safe walking. Normal gait patterns are encouraged and abnormal patterns corrected.
Jonathan Blood Smyth, editor of the Physiotherapy Site, writes articles about Physiotherapy, back pain, orthopaedic conditions, neck pain, injury management and physiotherapists in Gloucester. Jonathan is a superintendant physiotherapist at an NHS hospital in the South-West of the UK.
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