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Joints — The Cartilage & Tendon Economy
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In one pass A joint is not two bones meeting at a point.
Educational content, not medical advice — consult a clinician.
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Chapter 1
The seven parts of a joint
A joint is not two bones meeting at a point. It is a small team of tissues working together: the cartilage pads, the synovium and its fluid, the capsule and ligaments, tendons, a meniscus or labrum, bursae, and the proprioceptive nerves that tell the brain how far the joint is bent. When any one of them falls behind, you can feel pain.
Remember one thing first: of those seven, only the synovium, the capsule and the ligaments have their own blood supply. Cartilage and the inner part of the meniscus have none. They depend on you pressing down, letting go and pressing again, which squeezes nutrients in from the joint fluid. How to look after a joint, and how to train it, follows from that one fact.
Remember one thing first: of those seven, only the synovium, the capsule and the ligaments have their own blood supply. Cartilage and the inner part of the meniscus have none. They depend on you pressing down, letting go and pressing again, which squeezes nutrients in from the joint fluid. How to look after a joint, and how to train it, follows from that one fact.
Mechanism · Why joint fluid gets slicker as you move
The seven parts of a joint (the review by Sophia Fox 2009):Articular cartilage: a 2–4 mm clear pad capping the bone ends, made mainly of type II collagen, glycosaminoglycans (GAGs, long sugar chains that hold large amounts of water) and about 80 % water. It has no blood vessels, no nerves and no lymph vessels. Its ability to squash and spring back, and its near-frictionless surface, come entirely from the GAG network holding water in place.Synovium and synovial fluid: the synovium is a thin layer of cells that secretes hyaluronic acid (HA) and lubricin. The fluid has an odd temper: thick at rest, it turns thinner and slicker the moment it is loaded and sheared (Jay & Waller 2014).Capsule and ligaments: dense type I collagen that binds the two bones together and stops the joint from bending to extreme angles.Tendons: carry the pull of muscle to bone; also type I collagen, plus a little elastin.Menisci and labra (in the knee, hip and shoulder): fibrocartilage that helps spread load and enlarges the contact area.Bursae: small sacs between tendons, skin and bone that reduce friction.Proprioceptive nerve endings: tucked into the capsule and ligaments, they keep telling the brain what angle the joint is at.
Why does the knee feel stiff on the first step after sitting, then loosen after a few paces?
Synovial fluid is not an ordinary liquid but a non-Newtonian fluid. At rest, the long chains of hyaluronic acid tangle together and it is thick, like a gel; when the joint is loaded and the surfaces slide, the chains line up in the direction of movement, the thickness drops sharply, and a nearly frictionless film forms between the two cartilage faces.Lubricin is a protein on the cartilage surface that provides boundary lubrication: even when the two faces are pressed almost together, it still lets them glide past each other (Jay & Waller 2014).So the first step up from a chair feels stiff and clears after a short walk: the hyaluronic-acid chains have not lined up yet, and the fluid has not turned slick.
What it means for you:
A joint that clicks but does not hurt usually is not wearing out; the common causes are small gas bubbles popping in the joint fluid and the sound of tissue gliding past, and it needs no treatment.My joints need lubricating is not solved by swallowing something: oral hyaluronate barely reaches the joint cavity. Trials of hyaluronate injected into the joint give mixed results, and Cochrane's review of this viscosupplementation dates from 2006 (Bellamy 2006); it is not a first-line treatment.The most direct way to make joint fluid slick again is to move — walk for a few minutes.
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Chapter 2
Cartilage is fed by movement
Cartilage has no blood supply, so how does it stay alive? By being pressed, released and pressed again: each step squeezes nutrients from the joint fluid into the cartilage matrix and squeezes waste out. For cartilage, long-term immobility is one of the real enemies.
Does that mean more is always better? No. In observational studies the pattern looks more like a curve that is worse at both ends: people with moderate activity show the slowest progression on imaging markers of cartilage breakdown, while very low and very high activity both do worse. A better way to put it: cartilage fears being starved more than being used. Loading is its lunch.
Does that mean more is always better? No. In observational studies the pattern looks more like a curve that is worse at both ends: people with moderate activity show the slowest progression on imaging markers of cartilage breakdown, while very low and very high activity both do worse. A better way to put it: cartilage fears being starved more than being used. Loading is its lunch.
Evidence · What disuse and overuse do to cartilage
The cost of not moving can be measured:In studies of healthy men kept in head-down bed rest for 21 days, blood markers of cartilage metabolism (cartilage oligomeric matrix protein, COMP, and the matrix metalloproteinase MMP-3) fell by more than 20%, and returned to their earlier levels within 1 day of getting up (Liphardt 2018, two crossover studies of 7 and 9 men). That shows cartilage metabolism is sensitive to loading; it does not show that cartilage was permanently harmed.In long spells without weight-bearing, such as immobilization after surgery or paraplegia, cartilage thins; the evidence for this is solid (the Eckstein 2006 review). In the other direction, elite athletes' average cartilage thickness is not increased by heavy training.
Is more always better? No — it looks more like a U-shaped curve:
Lin 2013 followed 205 middle-aged people aged 45–60, with no knee pain and no arthritis, for 4 years. Physical activity was scored by questionnaire, and an early marker of cartilage breakdown (the T2 value) was measured with 3 T MRI. Both the most active third and the least active group progressed faster than people with moderate activity. This is an observed association.In the randomized trial of Roos & Dahlberg 2005, 45 adults at high risk of knee arthritis, who had had part of a meniscus removed 3–5 years earlier, were assigned either to supervised exercise 3 times a week for 4 months or to no intervention. Among the 30 who could be compared at the end, the GAG measure in the exercise group's cartilage improved while the control group's declined. That is not growing a new layer of cartilage; it is holding on, or improving.Alentorn-Geli 2017 pooled 17 studies with 114,829 people in total: hip and knee arthritis was found in 3.5 % of recreational runners, 10.2 % of sedentary people and 13.3 % of elite competitive runners. These are observational data, but they do not support the idea that running itself grinds joints down.
"I sit 12 hours a day — what about my joints?"
The issue is not high pressure from sitting (joint pressure while seated is actually low). It is the absence of load-and-release cycles.In cartilage tissue and cell experiments, cartilage cells held under steady pressure for a long time shift toward breaking down: enzymes that degrade cartilage (MMP-13, ADAMTS-5) go up, and the making of type II collagen and aggrecan goes down.
In practice (steps reasoned from mechanism; no trial has used cartilage as its endpoint):
After 30–45 minutes of sitting, get up and move for 1–2 minutes. It is a free feeding signal for cartilage, nothing to do with burning calories.Use the full range of motion when you train: full-depth squats, lunges and hip hinges load cartilage better than half-range work.Avoid both ends: complete immobility (long bed rest, sitting all day) and years of high-volume, high-impact training sit on the two falling ends of the U.
Chapter 3
Tendons barely renew in adulthood
The core of a tendon, laid down before you stop growing taller (roughly before age 17), stays with you for life. The load-bearing collagen is laid down during the growing years and barely renews after that. The tendon's edges and the sheath around it still turn over, but the core fibers that actually carry the load — what you have as an adult is what you keep.
So how does an injured tendon heal? Not by swapping in a new batch of collagen, but by letting the matrix between the load-bearing fibers catch up. Gradual loading is the main route with randomized trials behind it: eccentric training, or heavy, slow resistance training. You cannot replace the rebar, but you can rebuild the cement between it.
So how does an injured tendon heal? Not by swapping in a new batch of collagen, but by letting the matrix between the load-bearing fibers catch up. Gradual loading is the main route with randomized trials behind it: eccentric training, or heavy, slow resistance training. You cannot replace the rebar, but you can rebuild the cement between it.
Evidence · Two loading programs for tendinopathy
Heinemeier 2013 used the carbon-14 left over from nuclear-bomb tests to date 28 samples of adult Achilles-tendon core. The carbon-14 level in the tendon core roughly matched the atmosphere during the first 17 years of each person's life, showing that the core is laid down while you are growing taller and is essentially not renewed after that; muscle samples measured alongside showed continuous renewal. This is about the hardest-working bundle of core fibers, not the whole tendon — proteins inside cells, the tendon's edges and the sheath around it still turn over normally.How an injured tendon heals — what the trials say:
Heavy eccentric training (Alfredson 1998): 15 recreational athletes with chronic Achilles tendinopathy (average age 44) did straight-knee and bent-knee heel drops, 3 × 15 of each, twice a day. After 12 weeks, all of them were back to their previous level of running; 15 people with the same diagnosis treated in the conventional way all ended up having surgery. This was a prospective study without randomization. Later controlled trials support eccentric training, but the results are less uniform — not everyone recovers.Heavy slow resistance (HSR, Kongsgaard 2009): 39 men with patellar tendinopathy were randomized to steroid injections, eccentric decline squats or HSR for 12 weeks. All three groups had improved at 12 weeks. At the six-month follow-up, the gains held in the eccentric and HSR groups but faded in the injection group; the HSR group was the most satisfied, and collagen turnover in the tendon increased.Sleep and growth hormone: Doessing 2010 gave healthy young adults growth-hormone injections for 14 days (33–50 µg per kilogram of body weight a day). In tendon, type I collagen gene activity rose about 3.9-fold and tendon collagen synthesis about 1.3-fold; the nearly 6-fold rise (5.8-fold) was in muscle collagen synthesis, and it did not reach statistical significance (P = 0.06). Growth hormone is released mainly during deep sleep, a conclusion from observational research (Van Cauter 2000). Linking the two, poor sleep means poorer tendon repair is an inference from mechanism: no one has tested the whole chain in one trial, and the injected doses are far beyond anything sleep provides. Treat good sleep as a plausible part of tendon rehab, not as a proven treatment.
How the two programs actually work:
The Alfredson Achilles program (for chronic Achilles tendinopathy, not for an acute tear):
Stand on the ball of the injured foot at the edge of a step and use the good leg to rise to the top → lower slowly on the injured leg alone until the heel drops below the step → use the good leg to get back up (the injured side does no upward push).3 × 15 with the knee straight, plus 3 × 15 with the knee bent: 90 repetitions a session.Twice a day: 180 repetitions a day.Keep it up for 12 weeks. Mild pain during the exercise is allowed — not ignoring pain, but pain that does not get worse as you go is acceptable.Once it stops hurting, add load gradually with a weighted backpack.For an acute tear, a complete rupture, or a joint that is red, swollen and hot: do not do it; see a doctor.
Heavy slow resistance (Kongsgaard's patellar-tendon program):
Two-legged lower-body strength movements with heavy loads, each repetition lowered slowly and pushed up slowly.Start with a lighter load and add weight week by week.The trial ran for 12 weeks.The total volume is far less than Alfredson's 180 a day, and it is easier to stick with. Set the exact sets, repetitions and pace of progression with a physiotherapist.
Neither is a do-it-yourself recipe: have a physiotherapist or sports-medicine doctor guide the first few weeks. An acute injury and chronic tendinopathy are different things: an acute injury is protected and unloaded for a while first; the loading programs above are for chronic tendinopathy.
Chapter 4
Why athletes' joints don't fall apart
People often say athletes wear their joints out, knees first. The observational data point the other way: recreational runners actually have lower rates of hip and knee arthritis than sedentary people. The main known risks are an old joint injury, higher body weight and weak thigh muscles — not how many kilometers you run each week.
What athletes get right comes down to a few things: loading their joints year after year, strong muscles around them, sharp proprioception, weight kept in check, enough sleep, and using the full range of motion. You do not have to become an athlete. Getting two or three of these right already moves you toward the better end.
What athletes get right comes down to a few things: loading their joints year after year, strong muscles around them, sharp proprioception, weight kept in check, enough sleep, and using the full range of motion. You do not have to become an athlete. Getting two or three of these right already moves you toward the better end.
Myth · Creaky knees mean you are too old to train
Alentorn-Geli 2017 pooled 17 studies with 114,829 people. Hip and knee arthritis was found in 3.5 % of recreational runners, 10.2 % of sedentary people and 13.3 % of elite competitive runners. These are observational data; they show, at the least, that moderate running is not grinding joints down.Several findings point the same way:
Weakness of the quadriceps, the muscles at the front of the thigh, is a risk factor for knee arthritis getting worse over time (the cross-sectional study of Slemenda 1997; the review by Roos & Arden 2016). The reverse also holds as an observed association: people with strong thigh and stabilizing muscles show slower joint degeneration.Training itself changes cartilage shape very little, but unloading (immobilization, bed rest, paraplegia) reliably thins cartilage (Eckstein 2006). Cartilage is asymmetric this way: disuse harms it quickly, and use rebuilds it slowly.So the main known risks are an old joint injury, higher body weight (a high , body mass index) and long-term inactivity — not weekly mileage.
Sports-medicine specialists generally agree that athletes get roughly these six things right:
1. Loading their joints year after year: cartilage and tendon keep getting the signal that they are still needed, so their metabolism stays tilted toward building.
2. Strong thigh muscles and hip abductors: shocks from random directions are absorbed by muscle instead of landing entirely on the joint surfaces.
3. Sharp proprioception: just before an ankle roll or a fall, the nerve loop braces the joint before soft tissue can tear.
4. Weight kept in check: Messier 2005 measured, in 142 overweight older adults with knee arthritis, that each 1 kg of weight lost meant about 4 kg less force on the knee with every step while walking — which adds up over thousands of steps a day.
5. Enough sleep: growth hormone is released mainly in deep sleep, and it is a signal for collagen building; this link is reasoned from mechanism.
6. Using the full range of motion: not living in the protective middle of the range, but actually taking the joint to its end.
You can train in your eighties and nineties: in Fiatarone 1990, 10 nursing-home residents averaging 90 years old did 8 weeks of high-intensity strength training. In the 9 who finished, quadriceps strength rose by an average of 174 % and tandem walking speed by 48 % (there was no control group). The randomized trial that followed, Fiatarone 1994 in the NEJM, enrolled 100 frail older people averaging 87 years old for 10 weeks: strength rose 113 % in the training group and walking speed 11.8 %, while strength barely changed in those who did not train; 94 % completed the study.
Do deep squats hurt the knees? The literature review by Hartmann 2013 concluded that, with good technique and gradually increased load, deep squats are no harder on the knees and lower back than half or quarter squats.
Three things to take home:
A joint that cracks but does not hurt usually needs no treatment.Too old to train is a cultural story, not biology: starting strength training in your eighties or nineties still builds real strength.What deserves real caution is the combination of an old joint injury, long-term inactivity and higher body weight — not weekly mileage.
For the supplement side, the Glucosamine + Chondroitin story and the Collagen peptides story each go into detail.
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Chapter 5
What the guidelines recommend
Two independent international guidelines, OARSI 2019 (the Osteoarthritis Research Society International) and ACR/AF 2019 (the American College of Rheumatology with the Arthritis Foundation), agree closely on how to treat knee osteoarthritis first. None of the first-line levers is a supplement.
First line is structured exercise, weight loss if you are overweight, a topical anti-inflammatory rubbed on the joint when needed, and targeted strength rehab. Tendinopathy is a different matter, treated with eccentric or heavy slow resistance training. Most people with knee osteoarthritis should start with these.
First line is structured exercise, weight loss if you are overweight, a topical anti-inflammatory rubbed on the joint when needed, and targeted strength rehab. Tendinopathy is a different matter, treated with eccentric or heavy slow resistance training. Most people with knee osteoarthritis should start with these.
Clinical · What the guidelines put first, and reject
What the two guidelines strongly recommend and put first:Structured land-based exercise: strength training, aerobic exercise and full-range movement. This is the strongest tier of evidence, backed by many randomized trials.Weight loss (if you are overweight or obese): in the Framingham cohort, women whose fell by 2 units or more over 10 years (a loss of about 5 kg) had less than half the odds of developing symptomatic knee arthritis ( 0.46); this is an observed association (Felson 1992). In the IDEA randomized trial (454 overweight adults with knee arthritis, 18 months), the diet-plus-exercise group had the largest drop in WOMAC pain score (−3.0), more than diet alone (−1.8) or exercise alone (−1.7) (Messier 2013).Topical non-steroidal anti-inflammatory drugs (): diclofenac patches or gel rubbed on the joint. The drug stays mostly where it is applied, whole-body side effects are small, and it is a first choice for older adults.Self-management education and tai chi: both carry ACR's strong recommendation.Short courses of oral anti-inflammatory painkillers when needed: strongly recommended by ACR, conditionally by OARSI.A one-off corticosteroid injection into the joint: it does relieve pain in the short term, but do not have it repeated; the chapter on injections and supplements explains why.
Used only case by case: hyaluronate injected into the joint (guidelines disagree, and it is not a first choice), and aids such as a cane, knee brace or taping, chosen to suit the individual.
Tendinopathy is not arthritis and follows a different plan:
Alfredson eccentric training or Kongsgaard's heavy slow resistance (HSR); see the chapter on tendons.Isometric holds (Rio 2015): in a crossover study of 6 volleyball players with patellar tendinopathy, one session of 5 knee-extension holds of 45 seconds each relieved pain clearly on the spot, and the effect lasted at least 45 minutes. Later studies have given mixed results, but it can still serve as a tool for short-term pain relief.
Why are glucosamine and chondroitin not on the first-line list?
ACR 2019 gives a strong recommendation against glucosamine alone, or combined with chondroitin, for knee and hip osteoarthritis; OARSI 2019 likewise strongly recommends against every glucosamine and chondroitin product.
Why are both guidelines so firm?
The GAIT trial (Clegg 2006, NEJM): 1,583 people with knee arthritis took the pills for 24 weeks, and the primary endpoint was the share whose WOMAC pain fell by at least 20%. The response was 60.1% with placebo and 64.0% with glucosamine alone (P = 0.30); the combination added 6.5 percentage points (P = 0.09) — neither significant — while celecoxib, the active comparator, added 10.0 points (P = 0.008). In the moderate-to-severe pain stratum set up in advance by pain severity (354 people), the combination responded 79.2% against 54.3% on placebo (P = 0.002), but the authors themselves call this exploratory. In the 2-year continuation (Sawitzke 2010), no group beat placebo and the moderate-to-severe signal did not repeat; the structural study of joint-space width on X-rays (Sawitzke 2008) was also negative. So guidelines do not treat that subgroup as a basis for recommendation.Wandel 2010 (a network in the BMJ, 10 randomized trials, n > 3,800): glucosamine and chondroitin, alone or together, did not reduce pain by the smallest amount patients can notice.
Is European prescription-grade crystalline glucosamine sulfate different?
The prescription sulfate made to the Rotta formula showed some signal in older European trials, but newer, higher-quality research (such as the LEGS trial and the Roman-Blas 2017 meta-analysis) did not find that signal.If you already take it, it is generally well tolerated (tell your doctor if you take warfarin), but do not expect it to change joint structure, and do not let it crowd out exercise and weight loss; see the Glucosamine + Chondroitin story for detail.
Do collagen peptides fix joints? In one trial (Clark 2008), 147 university athletes with activity-related joint pain but no joint disease took collagen hydrolysate for 24 weeks; only 97 could be evaluated, and their pain scores fell a little more than with placebo. No clinical guideline lists collagen peptides as a first-line treatment for osteoarthritis. See the Collagen peptides story for detail.
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Chapter 6
Injections and pills with weak evidence
Most of the premium-sounding upgrades are not supported by their trials. Glucosamine plus chondroitin missed its primary endpoint in the largest trial; collagen peptides are not a standard treatment for arthritis; and repeated steroid injections into the joint relieve pain no better than saline while cartilage thins more. One or two short-term injections for a flare are still fine.
When you hear about any upgrade, ask two things first: where does it rank in the OARSI 2019 or ACR 2019 guideline, and was the largest trial positive on its primary endpoint? If the answer to both is no, it is not an upgrade. It is marketing.
When you hear about any upgrade, ask two things first: where does it rank in the OARSI 2019 or ACR 2019 guideline, and was the largest trial positive on its primary endpoint? If the answer to both is no, it is not an upgrade. It is marketing.
Evidence · What trials say on injections and rest
Start with the three most heavily marketed options — two you swallow and one injected into the joint.1. Glucosamine plus chondroitin: the GAIT trial was negative on its primary endpoint, and the network of Wandel 2010 found that it did not relieve pain by an amount patients could notice (the chapter on the guidelines and the Glucosamine + Chondroitin story go into more detail).
2. Collagen peptides and type II collagen: the eat it to grow it intuition is taken apart in the Collagen peptides story. The study of gelatin with vitamin C (Shaw 2017) had only 8 healthy men and found that one blood marker of collagen synthesis doubled; it did not measure injury or recovery. It is not a standard treatment for arthritis, and no major guideline lists it as first-line.
3. Repeated corticosteroid injections into the joint: in the randomized trial of McAlindon 2017, 140 people with symptomatic knee arthritis and synovitis on ultrasound received 40 mg of triamcinolone or saline every 12 weeks for 2 years. The steroid group lost more cartilage thickness (−0.21 vs −0.10 mm), yet its WOMAC pain score did not differ significantly from saline (−1.2 vs −1.9).
A rough threshold for judging anything: was its largest trial at least 200 patients, followed for at least 12 months, and positive on its primary endpoint?
4. Platelet-rich plasma (PRP) injected into the joint: in the RESTORE trial (Bennell 2021, JAMA), 288 people with knee arthritis were followed for 12 months, and PRP made no difference to pain or cartilage volume compared with saline. In high-quality blinded trials PRP has not beaten placebo; some of the early positive small studies may reflect a lack of blinding.
5. Hyaluronate (HA) injected into the joint: the Cochrane review (Bellamy 2006) found a small short-term effect and an uncertain long-term one. It is not first-line, and the two guidelines do not agree on it.
6. Long-term rest:
For the first 48–72 hours after an acute injury, relative rest and protection are reasonable; after that, getting moving early is better for cartilage and tendon recovery (covered in the chapters on cartilage and tendons). Long-term immobilization is not protection; it makes things worse.My joint is damaged, so I should move less puts cause and effect the wrong way round: not moving is exactly how cartilage starts to starve.
7. Joint patches, infrared lamps, pellets and magnets: most have no decent randomized trials behind them. A few (such as kinesiology tape) may make pain feel a little less in the short term, but that is not the same thing as treating osteoarthritis.
One more often-overlooked thing that does not work: arthroscopic surgery for a degenerative meniscal tear.
In the FIDELITY trial (Sihvonen 2013, NEJM), 146 people with a degenerative meniscal tear had either arthroscopic partial meniscectomy or sham surgery, and after 1 year there was no difference in pain or function.For a meniscal tear that is degenerative rather than caused by an injury, a period of exercise rehabilitation (commonly about 12 weeks) is a more sensible starting point than surgery. If a doctor suggests going straight to an operation, it is fair to ask whether 12 weeks of conservative treatment could come first.
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Chapter 7
Exercises for each joint
Whatever the joint, the underlying framework is the same: strength training two or three times a week, through the full range of motion; proprioception work such as single-leg balance; keeping your weight in check; and making sure deep sleep actually happens. If pain lasts more than a week, see a general practitioner or a physiotherapist.
The knee, hip, shoulder, ankle and lower back each have a short set of core exercises; two or three sessions a week is enough, not every day. If a joint becomes acutely swollen, red and hot, locks and cannot bear weight, or if you have pain in small joints on both sides of the body with morning stiffness lasting more than an hour, do not push through it — see a doctor.
The knee, hip, shoulder, ankle and lower back each have a short set of core exercises; two or three sessions a week is enough, not every day. If a joint becomes acutely swollen, red and hot, locks and cannot bear weight, or if you have pain in small joints on both sides of the body with morning stiffness lasting more than an hour, do not push through it — see a doctor.
In practice · A joint-friendly training week
The underlying framework (for any joint):Loading: strength training 2–3 times a week, through the full range of motion.Proprioception: single-leg standing, a balance board, training on unstable surfaces.Body weight: keeping your (body mass index) in check does more than any supplement (Felson's finding in the Framingham cohort).Sleep: let growth hormone actually be released during deep sleep (Van Cauter 2000); a sleepless night harms more than just the brain.If pain lasts more than a week, that is when to see a general practitioner or a physiotherapist.
For each joint, the core exercises below are enough at 2–3 sessions a week — not every day:
Knee: goblet squats, Bulgarian split squats and full-range lunges, plus single-leg deadlifts and terminal knee extensions; to progress, you can train squat patterns with the knees traveling past the toes.Hip: hip hinges (Romanian deadlifts, good mornings), hip abduction (clamshells, side-lying leg raises) and hip rotation (the 90/90 stretch). For people who sit a lot, the first things to fix are tight hip flexors and weak hip extensors.Shoulder: scapular retraction and depression, external-rotation work (Y-T-W), then full pushing and pulling (overhead press plus pull-ups). Do not train only the front of the shoulder; the main source of shoulder stability is the back.Ankle: single-leg calf raises, eccentric heel drops (worth doing even without an injury) and single-leg balance (30 seconds × 3); warm up before running or court sports.Lower back: McKenzie extensions and hip hinges, plus dead bugs, bird dogs and side planks (Stuart McGill's big three), plus hip abduction. Do not make isolated back-extension work your main strategy; what the lower back really needs is the abdominal muscles, hips and spine bracing together.
A few red lines: if one appears, stop training through it and see a doctor:
A joint that suddenly becomes swollen, red and hot: it may be an infection, a gout attack or acute crystal arthritis; see the Gout & Hyperuricemia story.A joint that locks, or cannot bear weight after an injury: it may be an acute meniscus or ligament injury.Pain in small joints on both sides of the body (the knuckles, the wrists), with morning stiffness lasting more than 1 hour, plus fatigue or a low fever: this is not the osteoarthritis pathway. Ask for a referral to rheumatology to check for rheumatoid arthritis or another autoimmune disease.A chronic dull ache, morning stiffness under 30 minutes, and feeling better once you move: most likely osteoarthritis; follow the OARSI / ACR first-line framework described earlier.
Monday and Thursday (strength days, 45–60 minutes each)
Warm-up: take each joint through its full range 5–10 times (shoulder circles, hip circles, unloaded hip hinges, walking lunges, calf raises).4–6 main exercises: squat, deadlift, push, pull, single-leg work, core. 6–12 repetitions × 3–4 sets, adding load gradually.Finish: cool down, plus 2 minutes of balance and proprioception work.
Tuesday, Friday and Saturday (aerobic work and movement)
30–50 minutes at moderate intensity: brisk walking, easy jogging, cycling, an elliptical machine, swimming.You do not have to run every time; rotating between several kinds is better than sticking to one.Aim for about 70–80 % of your maximum heart rate (HRmax): you can talk but not sing.
Every day (free, and the biggest lever)
Walk 8,000–10,000 steps. That is a general everyday activity target, not a figure from cartilage research.After 30–45 minutes of sitting, get up and move for 1–2 minutes — a loading signal for cartilage.Sleep 7–9 hours and let deep sleep actually happen (growth hormone is released mainly then; see the All-Nighter story).
Once a week (optional, but useful)
One full session of dynamic stretching and full-range movement (10–15 minutes): not static stretching, but moving through the full range under load.
How to tell whether it is working:
After 6–8 weeks, single-leg balance, squat depth and the subjective sense of creaky or stiff joints should all be better.If they are not: film your technique and compare, see a physiotherapist once or twice, and check the basics of nutrition and sleep.If symptoms get worse, or redness and swelling appear: stop and see a doctor.
References · 25
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- Jay, G. D., & Waller, K. A. (2014). The biology of lubricin: near frictionless joint motion. Matrix Biology, 39, 17–24. 10.1016/j.matbio.2014.08.008
- Liphardt, A. M., Mündermann, A., Andriacchi, T. P., Achtzehn, S., Heer, M., & Mester, J. (2018). Sensitivity of serum concentration of cartilage biomarkers to 21-days of bed rest. Journal of Orthopaedic Research, 36(6), 1465-1471. 10.1002/jor.23786
- Eckstein, F., Hudelmaier, M., & Putz, R. (2006). The effects of exercise on human articular cartilage. Journal of Anatomy, 208(4), 491–512. 10.1111/j.1469-7580.2006.00546.x
- Lin, W., Alizai, H., Joseph, G. B., Srikhum, W., Nevitt, M. C., Lynch, J. A., McCulloch, C. E., & Link, T. M. (2013). Physical activity in relation to knee cartilage T2 progression measured with 3 T MRI over a period of 4 years: data from the Osteoarthritis Initiative. Osteoarthritis and Cartilage, 21(10), 1558–1566. 10.1016/j.joca.2013.06.022
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