A stiff ankle sends the bill upward to the knee

When the shin cannot travel forward over the foot, the load has to be absorbed somewhere, and the neighbouring joints pay it.

Ask an athlete to squat and watch the heel. If it lifts early, the ankle has run out of dorsiflexion, and everything above it is now improvising. That is not a technique fault. It is a mechanical constraint being solved by the only structures that still have room to move.

Landing is where it costs something. A soft landing needs the shin to rotate forward over a planted foot so the ankle, knee and hip can share the deceleration across a long travel. Restrict the first joint in that chain and the travel gets shorter. Ground contact forces rise because the same energy is absorbed over less distance and less time. The knee flexes further to compensate, or the foot pronates hard to steal a little extra range through the midfoot, or the athlete simply lands stiffer and lets the skeleton take it.

Each of those solutions has an address. More knee travel with a forward shin loads the patellar tendon. Extra pronation twists the tibia inward and changes how the kneecap tracks. Landing stiff sends the shock up as a wave, and the tissue that absorbs it is bone.

I am wary of blaming any single joint restriction for any single injury, because plenty of athletes have restricted ankles for a decade and never notice. But the pattern shows up too often in one particular group to ignore, which is athletes returning from a serious ankle sprain. That joint gets held stiff by scarring and by a nervous system that has decided the end range is dangerous, and the person then spends two seasons landing slightly differently on that side without ever knowing.

The cause matters as much as the finding. Some restriction is soft tissue and will yield to loaded work at end range within weeks. Some of it is the front of the ankle joint itself, where bone spurs form from repeated impingement and set a hard stop that no amount of calf stretching will move. Those two look identical on a tape measure and are completely different problems.

Which is why I distrust the ankle screening number on its own.

The measurement tells you the door is closed. It does not tell you whether the door is locked or the frame has changed shape.