Physiotherapy And The Management Of Knee Replacement
Osteoarthritis is a time related joint degenerative condition, the incidence rising rapidly with age, making it the commonest arthritic condition in the world. It develops in various joints in the human body and in some people it particularly affects the large weight-bearing joints of the hip and the knee. As the joint surfaces deteriorate the joint becomes painful, crunches, loses range of motion and becomes difficult to walk on. When conservative measures are not helpful, such as physiotherapy, analgesics, walking aids and weight loss, then knee replacement is considered.
Total knee replacement is one of the most successful medical technologies with the highest quality of life improvements of any medical intervention, a distinction it shares with total hip replacement. Knee replacement has matured from an experimental procedure of uncertain long-term outcome to a predictable and very common operation with very good results at ten years or more. As western populations age knee replacement is overtaking hip replacement as the most commonly performed joint replacement.
Metal and plastic components are inserted to replace the degenerative joint surfaces of the knee. In knee replacement these consist of four items:
* The metal femoral insert to replace the lower end of the femur which is the top half of the knee.
* 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.
* The patellar button is also of plastic and placed on the back of the kneecap to replace that surface.
The components are fixed in place using cement which acts as a grouting material rather than sticking anything. Knee replacement surgery causes weakness of the knee muscles, pain, inflammation and joint swelling, all important problems which the physiotherapist needs to treat promptly. Physios in hospitals often use Cryocuffs to provide cold therapy and compression which reduce the knee effusion and the post-operative pain. Analgesia is encouraged regularly and the physio teaches muscle activation of the quadriceps and knee flexion hourly to get the joint moving. Restoring the muscle control of the knee and gaining joint range of movement is the initial goal of the first few day of therapy.
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.