What the X-ray does not show.
When researchers scanned the knees of 991 adults aged 50 to 90, 61% of those with a torn meniscus had felt no knee pain, aching or stiffness in the previous month. The picture and the pain are two different things.
Take nearly a thousand people aged 50 to 90, chosen without any regard to whether their knees hurt, and look inside one knee each with an MRI scanner. Researchers in Framingham, Massachusetts did exactly that with 991 adults. A torn or worn meniscus, the rubbery cushion between the thigh bone and the shin bone, turned up in 19% of women in their fifties and in 56% of men aged 70 to 90.1
The more surprising number came next. Of the people whose scans showed a meniscal tear, 61% had felt no pain, aching or stiffness in that knee in the previous month.1 The damage was there. The pain was not.
This is one of the quiet puzzles of the ageing knee, and it matters to anyone who has been handed a scan report full of alarming words, or told the pictures look "fine" while every stair hurts.
When the picture and the pain disagree
The gap is not a one-off. In 2008 John Bedson and Peter Croft searched the literature for population studies that measured both knee pain and knee X-rays. Among people with knee pain, the share whose X-rays showed osteoarthritis ranged from 15% to 76%. Among people whose X-rays showed osteoarthritis, the share with pain ranged from 15% to 81%.2
Part of that spread comes down to method: how many X-ray views were taken, how pain was defined, who was studied. But the authors' conclusion was blunt. Knee pain is "an imprecise marker" of radiographic osteoarthritis, and X-ray results "should not be used in isolation" when assessing an individual patient.2
MRI, which sees far more than an X-ray, widens the gap rather than closing it. A meta-analysis published in the British Journal of Sports Medicine pooled 63 studies of adults with no knee symptoms and no history of knee injury. In groups with an average age of 40 or over, 43% of knees showed cartilage defects, 37% showed osteophytes (bony spurs), 21% showed bone marrow lesions and 19% showed meniscal tears.3
Changes found in knees that do not hurt
Pooled share of knees with each MRI feature, adults with no symptoms or injury, average age 40 or over
Source: Culvenor et al., British Journal of Sports Medicine (2019)
None of these people were patients. They were simply living in their knees.
What is actually changing inside
Osteoarthritis is often described as cartilage wearing away, but it is more useful to look at the whole joint, and one anatomical detail explains a great deal: cartilage has no nerves. A 2022 review puts it plainly: "Cartilage is aneural, but the soft tissues and the subchondral bone around joints are richly innervated."4 Cartilage can thin without sending a signal of its own. The tissues that can hurt are the synovium (the lining of the joint), the capsule around it and the bone beneath the cartilage.4
That bone matters. In a study of 401 people with knee osteoarthritis, bone marrow lesions, patches of abnormal signal on MRI in the bone just under the cartilage, were found in 77.5% of those with knee pain and in 30% of those without. Large lesions were almost entirely confined to people with pain: 35.9% against 2%.5
The meniscus, by contrast, was a weak guide in Framingham. Among people who already had osteoarthritis on X-ray, a tear was found in 63% of those with knee pain, aching or stiffness on most days and in 60% of those without.1
The volume knob in the nervous system
Pain is not a direct readout of tissue damage. It is produced by the nervous system, which can become more sensitive over time, so that the same pressure starts to hurt more. Researchers call this sensitisation, and inflammation appears to be one of its drivers.
The Multicenter Osteoarthritis Study tested 1,111 people, average age 67, who had or were at risk of knee osteoarthritis, measuring how much pressure it took to cause pain at the kneecap and at the wrist. Over two years, synovitis (inflammation of the joint lining) seen on MRI was linked to a fall in the pain threshold at the kneecap. Effusion, extra fluid in the knee, was linked to a fall in the threshold at the wrist, far from the knee itself. Bone marrow lesions were not linked to either measure.6
A lower threshold at the wrist suggests that what begins in one knee may change how the wider nervous system handles pain. It may also help explain why two people with near-identical scans can live very different days.
None of this means scans are meaningless. When researchers compared the two knees of the same person, a design that removes differences between people such as how sensitive they are to pain, X-ray features were strongly associated with pain, and narrowing of the joint space mattered more than bony spurs.7 Much of the mismatch, in other words, lies between people rather than within them.
What this means for older people and their families
England's NICE quality standard expects adults aged 45 or over with activity-related joint pain, and any morning stiffness lasting no longer than 30 minutes, should be diagnosed with osteoarthritis clinically, without imaging. Its reasoning: "There is often a poor link between changes visible on an X-ray, MRI or ultrasound scan and the symptoms of osteoarthritis." Imaging still has a place when another diagnosis is possible.8
For families, two things follow. First, pain is real even when the scan looks mild. A parent who says the stairs hurt is describing something their nervous system is genuinely producing, not exaggerating what the picture shows. Second, a bad scan is not a sentence. Plenty of knees with torn menisci, thinning cartilage and bony spurs belong to people who report no pain at all.
In daily life, the questions that matter are often practical ones: can they get up from a chair, walk to the shop, manage the stairs at home? We have written about the knee and its long middle years in an earlier piece.
That is the lens Veema works through. We design around standing up and walking at home, not around what a scan looks like. Whether an exoskeleton can help a particular knee is a question only studies with older adults can answer.
These figures describe the need. They are not results or claims about Veema.
Sources
- Englund et al., New England Journal of Medicine (2008): MRI of 991 adults aged 50 to 90 in Framingham: meniscal tear or destruction in 19% of women aged 50 to 59 to 56% of men aged 70 to 90; 61% of those with tears had no pain, aching or stiffness in the previous month; in people with radiographic OA, tears in 63% with symptoms vs 60% without. Abstract read via the Lund University record.
- Bedson and Croft, BMC Musculoskeletal Disorders (2008): Of people with knee pain, 15% to 76% had radiographic OA; of people with radiographic OA, 15% to 81% had pain; quotes "an imprecise marker" and "should not be used in isolation".
- Culvenor et al., British Journal of Sports Medicine (2019): 63 studies of asymptomatic, uninjured knees; pooled prevalence at mean age 40 or over: cartilage defects 43%, osteophytes 37%, bone marrow lesions 21%, meniscal tears 19%.
- Morgan et al., Frontiers in Endocrinology (2022): Quote that cartilage is aneural while soft tissues and subchondral bone are richly innervated; nociceptors innervate the joint capsule and synovium. No numbers used.
- Felson et al., Annals of Internal Medicine (2001): 401 people with knee OA: bone marrow lesions in 77.5% with pain vs 30% without; large lesions 35.9% vs 2%.
- Neogi et al., Arthritis and Rheumatology (2016): 1,111 MOST participants, mean age 67: synovitis linked to lower patellar pressure pain threshold over 2 years; effusion linked to lower wrist threshold; bone marrow lesions not associated.
- Neogi et al., BMJ (2009): Within-person knee comparison: radiographic features strongly associated with pain; joint space narrowing more strongly than osteophytes. No numbers used.
- NICE quality standard QS87, Quality statement 1: Diagnosis: Age 45 or over, activity-related joint pain, morning stiffness no longer than 30 minutes, diagnose clinically without imaging; quote on poor link between imaging and symptoms.
