Common Knee Problems

For Young Learners

Clinical Relevance

Knee problems fall into a few broad groups, and knowing the groups helps more than memorising names.

Some happen suddenly. A twist on a planted foot, an awkward landing, a tackle. Something tears and the knee swells quickly.

Some build up slowly. Running further than usual, a new sport, a growth spurt. The knee aches after activity and settles with rest, then comes back.

Some belong to growing bodies. While you are still growing, the soft areas near the ends of your bones are the weak point, so young athletes get different injuries from adults doing the same sport.

And some come with age, as the smooth surfaces inside the joint gradually thin.

For Patients

Function

The pattern of your symptoms is informative. Swelling within hours of an injury suggests bleeding inside the joint. Swelling over a day or two suggests irritation. Locking suggests something physically caught. Giving way suggests a stability problem.

None of these is diagnostic on its own, and each narrows the field considerably.

Clinical Relevance

Most knee trouble belongs to one of five families. Knowing which one you are in tells you roughly what to expect.

Sudden injuries to the soft tissues. A twist, a landing or a blow tears a ligament, a meniscus or a tendon. These usually swell within hours and often involve a memorable moment.

Overuse and load problems. Pain builds gradually, often after a change in activity, footwear or surface. The tissue has not failed; it has been asked for more than it could tolerate.

Kneecap problems. Pain at the front, worse on stairs, sitting for long periods and squatting. Common in teenagers and in active adults, and usually manageable without surgery.

Wear of the joint surface. Stiffness after rest, aching with activity, gradual loss of movement. More common with age, and strongly influenced by strength, weight and previous injury.

Inflammatory and infective causes. Less common, and important not to miss. A hot, swollen knee with fever needs assessment the same day.

For Medical Students

Clinical Relevance

Knee presentations group usefully by mechanism rather than by structure. Acute traumatic soft tissue injury, overuse and load related disorders, patellofemoral pain and instability, degenerative joint disease, and inflammatory or infective arthropathy together account for the large majority.

Chronology discriminates well. A haemarthrosis developing within hours of injury implies bleeding and raises the probability of cruciate rupture, osteochondral fracture or peripheral meniscal tear. An effusion developing over twenty four to forty eight hours suggests synovial irritation. Insidious onset without trauma points towards degenerative, inflammatory or load related causes.

Mechanical symptoms are similarly discriminating. True locking, with a fixed block to extension, suggests an interposed fragment. Giving way suggests ligamentous insufficiency or quadriceps inhibition, and distinguishing the two matters.

Age shifts the differential substantially. Physeal injury and apophysitis belong to the skeletally immature. Ligamentous and meniscal injury predominate in young active adults. Degenerative change and crystal arthropathy predominate later.

Septic arthritis is the diagnosis that must not be missed at any age. A hot swollen knee with systemic upset requires same day assessment and aspiration before the picture is obscured.