Knee pain and knee osteoarthritis

What it is

Knee osteoarthritis involves the whole joint - cartilage, bone underneath it, the lining, the ligaments and the muscles that control it. Calling it wear and tear is misleading, because it implies a mechanical countdown that the evidence does not support: joint change and pain correlate poorly, and many people with substantial radiographic change have no symptoms at all.

The strongest modifiable factors are quadriceps and hip abductor strength, which control how quickly and how evenly load arrives at the joint. A weak leg lets the knee absorb load abruptly and lets it drift inward on every step - both of which are painful and both of which are trainable.

What it feels like

• Pain on stairs, particularly going down, before it hurts on the flat
• Stiff for a few minutes on standing after sitting, and stiff for a while in the morning
• Aching after activity rather than during it
• Grinding, clicking or a catching sensation
• Occasional swelling and a feeling of the knee giving way

What causes it

Most people have more than one of these at once, and they feed each other. Read the list looking for the two or three that sound like your week rather than for the one true answer — the ones that describe you are the ones worth acting on.

Quadriceps weakness

The quadriceps decelerate the body on every step and every stair. When they are weak the load arrives at the joint faster and less evenly. Quadriceps weakness predicts both pain and progression, and it is the single most reliable thing to train.

Hip abductor weakness

The glute medius stops the pelvis dropping and the knee falling inward on a single leg. Without it the knee collapses medially on every step, which loads the inner compartment - where most knee arthritis lives.

Stiff calves and ankles

Restricted ankle range changes the whole gait pattern and shifts load up the chain. It is a common and entirely fixable contributor that gets very little attention.

Tight hip flexors and a forward-tilted pelvis

Change the pelvis and you change the line the femur travels on. Sitting-driven hip flexor tightness alters knee mechanics on every stride.

Body weight

Each kilogram of body weight is several kilograms of load through the knee when walking and more on stairs. Weight change helps, and so does muscle change - and the muscle change is faster.

A previous knee injury

A meniscal tear, an ACL rupture or a significant fracture substantially raises the risk of arthritis decades later. This is one of the strongest predictors there is.

Inactivity

Cartilage has no blood supply and is nourished by movement pressing fluid in and out of it. A joint that does not move is a joint that is poorly fed, so rest is actively harmful over time.

Low-grade inflammation

Osteoarthritis involves genuine inflammatory activity in the joint lining, and systemic inflammation from excess fat tissue adds to it. This is part of why weight matters beyond the mechanical load.

Age and genetics

Both raise risk and neither is modifiable. They set the background rate; what happens on top of it is largely determined by strength, weight and activity.

Fear of using it

Believing the joint is wearing out makes people protect it, which weakens the muscles that protect it properly. The belief costs more function than the arthritis does in many cases.

Who tends to get it

• Anyone with a previous significant knee injury, particularly a meniscal or ACL injury
• People carrying extra weight, especially with low leg strength
• Adults over fifty, in whom prevalence rises steeply
• Anyone with a family history of osteoarthritis
• People whose work involves a lot of kneeling, squatting or heavy lifting

What makes it worse, and what settles it

The qFIT routine for this

Ready-made routineKnee Pain/Bulletproofing

qFIT already has this one built. It runs massage first, then stretching, then strength — the order that works on a body that is already sore — and every activity in it carries the reason it is there.

The button below opens your Checklist with this routine already selected, so instead of your whole list you land on just its Categories, Targets and Exercises, each with its checkbox, ready to tick as you work through them.

Have more than one problem? Tick yours under My Problems on My Profile and your Checklist's Routine list gains Recommended for my problems — every routine for the problems you picked, merged into one. Your picks stay private; that filter is the only thing they feed.

Get it checked if…

Locked knee; giving way; hot swollen joint with fever; inability to bear weight after trauma

And whatever the body part: chest pain or unusual breathlessness on exertion; a fever alongside the pain; unexplained weight loss; pain that is constant and unrelated to how you move; new numbness, weakness or loss of bladder or bowel control; or one calf that is swollen, warm and painful. Any of those, stop and get assessed.

How it usually goes

Exercise therapy produces pain and function improvements comparable to those from joint replacement in people with mild to moderate disease, and it is first-line in every major guideline. It takes eight to twelve weeks to show clearly and it must be continued - the gains fade when the training stops. Flares happen and do not mean the joint has deteriorated. A knee that locks, gives way repeatedly, is hot and swollen, or has changed suddenly is a different situation and needs assessing.

Prevalence basis: GBD 2021 and POLAR primary-care database

Others the same routine covers

These share the Knee Pain/Bulletproofing routine, so the work is the same. If one of them also sounds like you, that is a reason to expect more from it, not less.

This is general information, not a diagnosis, and it cannot examine you. If it matches you, use it to ask better questions of a clinician rather than to replace one.