Lifelong Knee Health

For Young Learners

Function

Knees last a long time if you look after them, and looking after them is less complicated than people think.

Keep moving. Joints are fed by movement. The slippery fluid inside only reaches the surfaces when the joint is used, so a knee that never moves is a knee that is poorly fed.

Build strength. Strong thigh and hip muscles take load off the joint and control how your leg lands when you run and turn.

Change things gradually. Most overuse injuries follow a jump in how much or how hard you are training, rather than the training itself.

Learn to land and turn. Programmes that teach this lower injury rates in young athletes, and they work best when a whole squad does them regularly through the season.

For Patients

Function

Four things carry most of the benefit over a lifetime.

Regular movement. Joint cartilage has no blood supply and depends on being loaded and unloaded to exchange nutrients. Activity within what the joint tolerates is associated with better joint health, not worse.

Muscle strength, particularly the quadriceps and the hip muscles. Strong muscles absorb load that would otherwise reach the joint surface, and they control the position of the limb during walking and landing.

Body weight. Every kilogram carried is multiplied several times at the knee during walking. Weight change is one of the few interventions that reduces the load itself rather than the response to it.

Gradual change. The large majority of overuse problems follow an increase in volume, intensity, surface or footwear within the preceding weeks.

Clinical Relevance

Some widely believed things matter less than people expect. Running does not appear to cause knee wear in healthy knees, and recreational runners have no higher rates than non runners in most studies. Cracking and clicking without pain is not a sign of damage. Supplements have a weak and inconsistent evidence base.

Previous injury is the strongest single predictor of future trouble, which is why rehabilitation after an injury is worth completing properly rather than stopping when the pain goes.

For Medical Students

Function

Articular cartilage is avascular and aneural, and derives nutrition by diffusion from synovial fluid driven by cyclical loading. Immobilisation therefore impairs cartilage health, and moderate loading maintains it. This underpins the general principle that activity within tolerance is protective rather than harmful.

Periarticular musculature attenuates load reaching the articular surface and governs limb position during stance and landing. Quadriceps weakness is both a consequence of knee pathology and a risk factor for its progression, which makes it a target as well as a sign.

Clinical Relevance

Modifiable factors with reasonable support are activity maintenance, muscle strengthening, body mass, and graduated progression of training load. Neuromuscular training programmes reduce injury incidence in young athletes, with adherence across a season appearing more important than the specific programme chosen.

Non modifiable and partially modifiable factors include previous injury, which is the strongest single predictor of subsequent injury, alignment, and sex.

Several widely held beliefs are poorly supported. Recreational running is not associated with increased degenerative change in healthy knees. Painless crepitus does not indicate structural damage. Nutritional supplements marketed for joint health have weak and inconsistent evidence.

Structured prevention programmes and their evidence are covered in the performance and prevention section rather than here.