Anterior cruciate ligament (ACL) sprain or rupture

What it is

The ACL is a short, strong cord inside the knee joint that stops the shin bone sliding forward under the thigh bone and controls rotation. A sprain is a stretch or partial tear, a rupture is a complete tear. Because it sits inside the joint and is bathed in joint fluid, a fully torn ACL does not usually heal back into a functioning ligament, which is why the decision about surgery is a real decision rather than a formality. The fast swelling after the injury is blood filling the joint from the torn ligament.

How volleyball causes it

Most volleyball ACL injuries involve no contact at all. The typical picture is a single-leg landing from a block or a spike where the knee collapses inward, the foot is planted, and the trunk is leaning away from the leg, so the whole rotation goes through the knee. The plant step of a slide approach is the same shape under speed, one leg decelerating and rotating at once. The other common version is contact only in the sense that you land on an opponent's or teammate's foot under the net, which locks the ankle while the body keeps turning. Beach players tear it far less often, because sand robs you of the sharp deceleration the injury needs.

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What it feels like

• A pop or loud snap that you hear or feel at the moment of injury
• The knee swelling up within a few hours, often within one hour. Fast swelling means blood
• A sense that the knee shifted, slipped or came apart for an instant
• Usually cannot continue playing, even if the pain settles quickly
• Once the swelling goes down, the knee gives way when you pivot, turn, or come down stairs
• A persistent feeling that you cannot trust the leg when you plant on it

Stop and get it seen if

• The knee looks deformed or out of place, or the foot below it is cold, pale, numb, or you cannot feel a pulse at the ankle. That suggests a knee dislocation with possible blood vessel or nerve injury and is a same-hour emergency.
• Cannot take any weight on the leg at all, or there is bony tenderness on the kneecap, the top of the shin, or the end of the thigh bone. Suspect fracture, which is more likely in a teenager whose growth plates are open.
• The knee is stuck bent and will not straighten, with a firm block at the end of the range. That suggests a torn meniscus caught in the joint and needs seeing quickly.
• The knee feels loose in more than one direction, or the lower leg can be moved around in ways it should not. Multiple ligament injuries need urgent assessment.
• Swelling that fills the joint within the first hour alongside severe pain.

What recovery usually looks like

Stages, not a schedule. Everyone moves through these at their own pace, and the ranges are wide because real recoveries are.

1. 1. Calm the joint and get the knee straight

   1 to 4 weeks

   Get the swelling down, restore full straightening, and wake the quadriceps back up. Straightening lost early is very hard to get back later.

   • The knee straightens as fully as the uninjured one when both heels are propped up
   • You can lift the straight leg without the knee sagging
   • Visible swelling has come down and the joint no longer feels tight when you bend
   • Walking without a limp

2. 2. Decide the path, build the knee either way

   4 to 12 weeks from injury

   Work out with a surgeon and a physiotherapist whether the plan is reconstruction or rehabilitation without surgery, while building strength that is needed regardless of the answer.

   • Full bending range restored
   • Thigh muscle wasting reversing rather than continuing
   • Single-leg standing controlled without the knee wobbling
   • No giving way during ordinary daily life

Ready to play again when

• Single hop, triple hop and crossover hop distances within about ten percent of the other leg
• Quadriceps and hamstring strength within about ten percent side to side, measured properly rather than guessed
• A single-leg block landing taken off balance stays controlled, with no inward collapse and no sense of the knee slipping
• No swelling the morning after a full training session with jumping and defence
• Formally cleared, with both time since surgery and objective testing satisfied, not one or the other

Keeping it from coming back

This is ordinary training, so unlike the rest of this page it does tell you what to do.

• Run a structured neuromuscular warm-up before every session, with jumping, landing, cutting and balance components. Programmes of this kind measurably reduce ACL injuries, and it is the single highest-value thing on this list.
• Nordic hamstring curls and Romanian deadlifts. Hamstring strength directly resists the shin sliding forward, and quad-dominant players carry more risk.
• Hip abductor and external rotator strength: banded lateral walks, side-lying abduction, single-leg Romanian deadlifts. If the hip cannot hold the thigh, the knee falls inward on landing.
• Coach landing technique explicitly. Two feet where the play allows, hips back, chest up, knee over the middle of the foot, and record it from the front occasionally so players can see their own knees collapsing in.
• Drill the slide approach plant and the single-leg block landing as skills at low intensity, rather than only ever doing them at full speed in a game.
• Enforce centre line discipline in training. A large share of contact ACL and MCL injuries in volleyball come from landing on someone else's foot under the net, and that is largely preventable.