Before discharge, nurses often tell patients that moving the feet a lot in bed helps prevent blood clots. Many family members hear this and feel reassured, thinking that as long as the older person keeps bending and straightening the ankles in bed, deep vein thrombosis will not come. There is nothing wrong with the advice itself, but it easily gives the impression that "moving the feet means complete safety". The real situation is far more complicated, and more important.
The most important principle first: for preventing clots after surgery, early movement is an effective part, but it cannot replace the anticoagulant medicine and compression devices prescribed by the doctor, and the movement with enough force is not swinging the feet while lying down but getting safely out of bed and walking with weight on the legs. Lying still slows blood flow in the leg veins and causes pooling, which easily forms clots. Getting the body moving again, especially standing and walking with weight on the legs, is one way of reducing such pooling. The sections below start from the causes of clots, set out where early movement really sits in the overall prevention strategy, compare exercise in bed with walking out of bed, and finally explain how home training and professional oversight should work together.
Three causes of blood clots after surgery
To understand how early movement helps, one first needs to know the three causes of clot formation (called the Virchow triad in medical textbooks): stasis of blood flow, a hypercoagulable state of the blood, and damage to the inner wall of the blood vessel. Surgery almost always triggers all three at once.
Seeing these three causes makes one point clear: early movement mainly deals with "stasis of blood flow", and the other two parts must rely on medicine and surgical management.Once the role of each is clear, there is no mistaken idea that "walking about means no need for medicine". For how bed rest itself makes the whole body decline and speeds up frailty, see the article on deconditioning and frailty in older people after surgery.
The roles of early movement and anticoagulant medicine
This section answers the core question directly: in preventing clots, early movement is a supporting measure that sits alongside drug and mechanical prevention, and none of them can replace another. Modern enhanced recovery after surgery (ERAS) programmes place "getting out of bed early" alongside drug prevention and mechanical prevention as elements of postoperative care. A pooled analysis of colorectal surgery found that patients who followed the full ERAS programme had about half the risk of complications of usual care, and a shorter hospital stay (Varadhan et al. 2010). Note, however, that this effect comes from the programme as a whole working together and not from moving the feet alone.
Two preventive measures the doctor is responsible for
- Drug prevention: blood thinners prescribed according to the type of surgery and bleeding risk, aimed at the problem of "hypercoagulable blood".
- Mechanical prevention: compression stockings and intermittent pneumatic compression devices that help blood return from the legs and reduce pooling.
- These two are the main measures in preventing clots, and whether anticoagulant medicine is used must follow the instructions of the treating doctor.
What physiotherapy is responsible for
- Early movement: using muscle contraction and walking to drive blood flow, reducing pooling caused by bed rest.
- Progressing step by step: the therapist sets a safe range of activity according to the site of surgery and the state of the wound.
- Early movement is a supporting measure and cannot replace medicine or compression devices.
The three main measures for preventing clots each have their own role, and it is not a matter of "choose one of the three". For example, never think that an older person who walks enough can stop blood-thinning medicine alone. Changing the dose of anticoagulant medicine or stopping it is decided entirely by the treating doctor. Early movement in physiotherapy builds on the prevention the doctor has already put in place to help the patient reduce pooling further, and the two cannot replace each other.
The difference between moving the feet in bed and walking out of bed
Many people treat "moving the feet" as the same thing as "preventing clots", overlooking the differences between kinds of activity. Actively bending and straightening the ankles in bed (ankle pumps) does drive the calf muscles to pump blood and is the easiest starting movement while lying down. But for pumping blood back to the heart, the force produced by standing with weight on the legs and walking a few steps is far greater than swinging the feet while lying down.
- Can be done any time: bend and straighten the ankles, rotate the ankles, and tighten and relax the calves while lying.
- A safe place to start: the first movement on the first day after surgery, when the wound still hurts.
- Limited drive: the pumping force of the muscle is small and the effect on pooling is mild.
- Position: a warm-up and a step along the way, not the end point.
- Enough pumping force: the calf muscles pump blood most strongly in weight-bearing walking.
- Several benefits at once: it also counters muscle loss, lung complications and a sluggish bowel.
- Needs oversight: graded by the site of surgery and balance, with someone beside the patient.
- Position: the main course when it is safe, and the earlier the better (under guidance).
"Having done some movement" and "having done enough movement" are therefore two different things. Exercise in bed is an important first step and a way to bridge the first two days when the wound hurts most, but the final aim is always to stand up and walk as soon as it is safe. Really getting out of bed and walking with weight is the main way of reducing blood pooling. For why the traditional idea of "resting in bed" should be given up after surgery, and when the first time out of bed is suitable, see the article on ERAS and early mobilisation after surgery, which explains the timing in more detail.
Key points that drive movement between bed and out of bed at home:
- Pump the ankles often—When awake, the patient can do a few sets of ankle bends and stretches every hour to make the calf muscles contract and reduce pooling of blood during bed rest.
- Stand and walk in stages—Activity should go step by step: first sit up at the bedside, stand holding on, and then walk short distances with a walking frame. Do not suddenly increase the amount of activity a lot at once.
- Several short walks beat one long one—Walking short distances several times a day is safer than pushing to walk until tired in one go, and it keeps blood flowing more consistently.
- Keep wearing the compression stockings—The patient must wear the compression stockings as the doctor instructs, and must not take off these preventive aids alone even when exercising.
Older people who need extra care when moving at home
After going home from hospital, early movement still has to continue, but two things need watching: first, getting the pace of progress safe, and second, recognising the warning signs of a clot. Older people, or those who are frail, generally recover less well after surgery. Compared with actual age, the degree of frailty better predicts the risk of postoperative complications and length of stay (Lin et al. 2016). These older people need early activity more, to stop their physical function declining further, but because balance and strength are weaker, they also need someone beside them when walking out of bed. To learn how to build fitness before surgery so as to go into the operation in better condition, see the article on prehabilitation before surgery.
The other point to watch is knowing the danger signs that need medical help at once. Sudden swelling, pain, warmth and redness in one calf or thigh are warning signs of deep vein thrombosis. If there is sudden breathlessness, chest pain or coughing up blood at the same time, a clot may have reached the lungs (pulmonary embolism), which is an emergency. In Hong Kong, in non-urgent situations the patient can first contact the treating doctor or follow up as arranged at the original surgical clinic. If the acute symptoms above appear, go straight to the accident and emergency department or call 999. In addition, community nursing and rehabilitation resources of the Hong Kong Anti-Cancer Society and the Hospital Authority clusters can also be linked up through the case manager at discharge.
When should a therapist be asked for help? If the older person is very afraid of getting out of bed to walk and does not dare to move at all after discharge, or is weak after surgery with poor balance so that family members find it hard to hold the person steady, or if family members do not know how far activity is safe, they should not work it out alone. Nova Health's registered physiotherapists provide home physiotherapy, assessing the patient's site of surgery, state of the wound and mobility, and demonstrating on the spot safe exercises in bed and the steps for getting out of bed and walking. The therapist also teaches carers the right holding technique and how to watch for the danger signs of a clot, so that the patient can be active early and safely and does not stay in bed too long out of too much worry.