Knee Sports Injury Physiotherapy
ACL Injury
- A pop at the time of injury
- Rapid swelling within hours
- The knee giving way on turning
- Difficulty fully straightening the knee
Quick answer
An ACL tear is a rupture of the ligament that stops the shin bone sliding forward on the thigh, usually from twisting or landing awkwardly. It causes a pop, rapid swelling and instability. Return to pivoting sport after reconstruction takes nine to twelve months, decided by testing rather than by date.
Typical recovery
9–12 months to unrestricted sport after reconstruction
A typical range, not a promise — how long it takes depends on how long it has been going on, and on what you do between appointments.
The anterior cruciate ligament stops the shin bone sliding forward and controls rotation at the knee. It tears most often without contact — landing from a jump, decelerating, or changing direction with the foot planted.
What happens at the time
Many people hear or feel a pop. The knee swells within a few hours, which distinguishes it from most other knee injuries where swelling develops over a day or two. Afterwards the knee often feels unstable, particularly on turning.
Surgery or not
Not everyone needs a reconstruction. People whose sport and work do not involve pivoting frequently do well with rehabilitation alone, building the hamstrings and quadriceps to compensate. Those returning to football, basketball, badminton or similar generally need the ligament reconstructed.
That decision belongs to the patient and the surgeon together, informed by how the knee performs after an initial rehabilitation phase.
Prehabilitation matters
Where surgery is planned, the weeks before it are not dead time. Going into surgery with a knee that straightens fully, has minimal swelling and reasonable quadriceps activation produces measurably better outcomes than operating on a stiff, swollen knee.
Rehabilitation after reconstruction
Broadly, and always to the surgeon's protocol:
- 0–2 weeks: control swelling, restore full extension, reactivate the quadriceps
- 2–6 weeks: restore full range, normalise walking, begin loading
- 6 weeks–3 months: progressive strengthening
- 3–6 months: running, then agility, jumping and landing mechanics
- 6–12 months: sport-specific work and graded return
Return to sport is tested, not scheduled
Strength of the operated leg is compared against the other side, along with hop tests, and a commonly used threshold is at least ninety per cent symmetry. Returning before that is the strongest predictor of tearing it again — and the re-injury rate for those who return early is substantial.
Medically reviewed by Nasir Mughees, BPT, MPT, Orthopaedic Physiotherapy · Last reviewed September 2026