After knee replacement surgery, many older adults want to kneel to pray and burn incense but cannot get up again, or want to squat to take something from the bottom drawer but cannot get down. The first thought is often a worry that something is wrong with the implant, or that the operation was not done well. This question deserves a serious answer.
The conclusion first. Being unable to kneel or squat low after knee replacement is very common, and five to eight in ten patients find it hard to kneel for a long time after surgery. Research has repeatedly shown, however, that this mostly comes from physical discomfort and the psychological factor of fear of damaging the implant. The joint is not truly unable to bend, and there is no evidence that kneeling damages the artificial joint. Squatting needs a bending angle of about 111° or more, and can be recovered through gradual practice (Wylde 2019; Mulholland 2001).
Does being unable to kneel mean the operation failed?
One point needs to be made clear first: poor ability to kneel is already quite common before knee replacement surgery, and it does not arise from the operation. In the Oxford Knee Score, kneeling has always been the item with the lowest score, and among the reasons that stop kneeling, a considerable proportion have no direct link with the operated knee (White 2016).
The conclusion first. Among knee replacement patients, being unable to kneel is common and is not an exception. It is mostly because of pain, discomfort, or worry about damaging the artificial joint, and not because the joint is structurally unable to kneel. At the same time, there is currently no evidence that kneeling itself damages the artificial joint (Wylde 2019; White 2016).
The proportion of patients who find it hard to kneel, or choose not to, after knee replacement
First, how common is it? Pooling several studies, about 50% to 80% of knee replacement patients say for a long time that it is hard to kneel or choose not to, which is one of the most common residual functional limits after surgery (Wylde 2019). Among these same patients, however, many are actually able to kneel.
In other words, although poor ability to kneel is common, "cannot do it" and "dare not do it" are two different things, and the second is often the larger group. To recover the ability to kneel and squat, it must first be sorted out which group the patient belongs to. For the criteria used to assess activity during the whole recovery period, see first the timetable for returning to daily life and sport after knee replacement.
The gap between what patients feel they can do and their actual ability to kneel
When researchers compared patients' "perceived ability" with their "actual ability under professional supervision", a clear gap appeared between the two. A study that followed 70 patients (100 replaced knees) showed that about 56% of people felt unable to kneel or chose to avoid it, but under the supervision of healthcare staff, all of the patients were able to kneel successfully, and eight in ten of them could kneel down easily and get up alone (Schai 1999). The same study also found that among patients who felt unable to kneel, nearly half (49%) held back because of worry about damaging the implant and a lack of correct information, which shows that the barriers are mostly cognitive bias and psychological fear, and not a mechanical limit of the joint.
- About 56% feel unable to kneel or simply avoid it (Schai 1999)
- Worry that one kneel will damage the implant, and worry about pain at the scar
- Give up before ever trying in a safe setting
- All 100 replaced knees could kneel under supervision (Schai 1999)
- Eight in ten of the same group could kneel down easily and get up again (Schai 1999)
- After an explanation and some support, the fear fades and they can try
Common reasons patients cannot kneel
Since the joints of most people are structurally able to kneel, where is the real obstacle? It comes mainly from three psychological and physical discomfort factors, and not from a problem with the joint itself. Pain and discomfort are the most common direct cause (White 2016). Many people worry that kneeling will crush the implant, and the scar and skin at the front of the knee feel tight. A lack of information and fear often make patients give up before they even try (Schai 1999).
Real reasons why kneeling is hard
- Pain and discomfort: the most common direct obstacle (White 2016)
- The scar and skin feel tight, and the feeling is stronger when kneeling on a hard floor
- Worry about damaging the artificial joint, or not daring to kneel for lack of correct information (Schai 1999)
Facts about kneeling and artificial joints
- There is currently no clinical evidence that kneeling on an artificial joint causes damage (Wylde 2019)
- Activities with large knee bending have no link to aseptic loosening of the artificial joint
- Main point to note: avoid rough ground scraping the skin over the scar
The right approach is therefore to remove the fear and try step by step in safe conditions, and not to avoid kneeling forever out of fear. This is the same rehabilitation idea of looking at actual function and not at fear, which is also used when judging when it is safe to drive again after knee replacement.
How much bending is needed to squat: at least 111°, and more for a deep squat
Compared with kneeling, squatting depends more on the knee bending angle, which also explains why a full deep squat is often the last to return. The deep squat and cross-legged sitting that Asian people are used to need far more knee bending than the everyday sitting and standing movements of Western people.
| Squatting / sitting cross-legged | These movements need a knee bending range of about 111° to 165° (or nearly fully folded). In addition, squatting low needs the hip to bend about 130° to fully, so it is harder than ordinary sitting down and standing up (Mulholland 2001). |
| Deep squat to the bottom | A study that measured a deep squat with the heels off the floor found that knee bending needs to reach about 157°±6°, close to the physiological limit of the human body. This explains why a full squat is the hardest to recover (Hemmerich 2006). |
| Ordinary sitting and standing in daily life | Most daily movements need only about 100 to 110° of bending. A half squat therefore usually returns earlier, while a full deep squat catches up only at the last stage. |
In other words, whether a person can squat is not a simple on-off switch. It is a continuous line that increases with the angle, and how far the active bending can go decides how low the body can squat. The actual bending angle needed for each daily movement can be checked against the knee bending angles needed for daily function, which turns "kneeling and squatting" into clear targets that can be measured.
How the ability to kneel improves over time
If a patient still cannot kneel in the first few months after surgery, it is too early to decide that it will never be possible. A pooled analysis showed that the proportion of patients able to kneel rises with time after surgery.
How to practise kneeling and squatting step by step
The practical way to recover kneeling and squatting is to break the psychological fear down into small controllable steps, and not to kneel straight onto a hard floor at the start. The basic precondition is that the wound and joint swelling have settled. Then start from a higher position, use a soft pad, and move down to the floor step by step.
Once the wound and swelling are confirmed to have settled, kneeling and squatting can be practised step by step in the following directions:
- Start from a high position—First try kneeling on a soft pad on something with some height, such as a sofa or chair, and practise getting up and sitting down. Once the joint is used to bending and weight bearing, lower the height step by step.
- Add a thicker pad—When kneeling, a thick kneeling mat or soft pad can ease the pressure pain at the scar and the front of the knee. Never kneel directly on rough hard ground, to avoid scraping the skin over the wound.
- Squat within your limits—Hold on firmly before squatting down slowly, and stop as soon as the knee feels tight or painful. Practise a half squat first and then go a little lower, and do not force a deep squat to the bottom at the start.
- Remove the fear first—Once the patient understands that there is no evidence that kneeling damages the artificial joint, trying with someone holding and guiding often shows that the patient can in fact kneel (Schai 1999).
When to ask for help from healthcare staff
Most discomfort when kneeling and squatting is part of a normal recovery process, but if any of the following warning signs appears, a healthcare professional should assess the patient, and the patient should not force it or give up treatment altogether:
- Persistent severe pain on kneeling or squatting that does not go away after rest
- Clear swelling or heat in the knee joint, a feeling of instability, or a feeling of the leg giving way
- No progress in the bending angle for several weeks, and the target range cannot be reached even when stretched with outside force
- Redness, swelling, broken skin or discharge at the wound after kneeling
- If none of the above applies and the skin simply feels tight or the patient is afraid of pain, it is mostly within the range that can be practised safely and step by step
When to ask a physiotherapist for help
When a patient is stuck at "cannot kneel and cannot squat low" and cannot tell whether the joint really cannot do it or the patient is simply afraid, that is the time to ask for a professional assessment. When assessing the ability to kneel and squat after knee replacement at home, the therapist first measures the patient's actual active bending angle and compares it with the standard that "squatting needs about 111°", working out accurately how many degrees are still missing, and does not just say in general terms that the patient "cannot kneel". Turning an abstract fear into an angle target that can be measured is the key to closing the psychological gap between "thinking kneeling is impossible" and "actually being able to kneel". Next, once the wound and swelling are confirmed to have settled, the therapist guides practice starting from a high position such as a chair seat or sofa, with a thick soft pad, and moves down to the floor step by step, while dealing with the two most common barriers, pain and worry about damaging the implant. The registered physiotherapists at Nova Health provide home physiotherapy, assessing and grading item by item according to the patient's current functional state. When an older adult blames himself for being unable to kneel, the therapist also explains on the spot that this is a common long-term limit after surgery, mostly from fear of pain and worry about damaging the implant, and not because the joint is unable to do it.
Local information in Hong Kong. In daily life in Hong Kong, older adults often need to squat to get things from the bottom of a cabinet, to pray and burn incense, to wipe the floor, or to squat in the market to choose vegetables. These movements demand far more knee bending than Western habits do, and they are the movements that older adults after knee replacement most want to recover but that return last. In addition, the floors of many tenement and older buildings are hard, and kneeling directly on them easily scrapes the skin and causes pain. To ask about physiotherapy referral in the public system and home exercise guidance, call the Hospital Authority hotline (2300 6555), and combine this with a home assessment to turn the bending angle targets into daily life.