An ACL injury is a partial or complete tear of the anterior cruciate ligament, a tough band of tissue connecting the thighbone to the shinbone inside the knee. It typically causes immediate swelling, a feeling of instability, and sharp pain that makes weight-bearing difficult. Recovery depends on the grade of tear, activity goals, and the quality of rehabilitation.
What exactly does the ACL do?
The anterior cruciate ligament sits deep inside the knee joint, running diagonally from the back of the femur to the front of the tibia. Its primary job is to prevent the tibia from sliding forward under the femur and to control rotational forces during pivoting movements. Without a functioning ACL, the knee loses its ability to handle sudden direction changes and deceleration.
Most people don’t think about their ACL until it fails. That failure is rarely subtle. A 2016 systematic review published in the British Journal of Sports Medicine estimated that ACL injuries occur at a rate of approximately 68.6 per 100,000 person-years in the general population, with significantly higher rates among athletes in cutting and pivoting sports (Montalvo et al., 2019, Br J Sports Med). Women are two to eight times more likely to sustain an ACL injury than men in the same sport, likely due to differences in neuromuscular control, landing biomechanics, and hormonal factors.
How does an ACL tear actually happen?
Roughly 70% of ACL injuries are non-contact. The classic mechanism involves a sudden deceleration combined with a change of direction, an awkward landing from a jump, or a pivot on a planted foot. Football, basketball, skiing, and padel are common culprits on the Costa del Sol.
Contact injuries account for the remaining 30%. A direct blow to the outside of the knee while the foot is fixed, common in rugby or football tackles, can force the knee inward and rupture the ligament. One important clinical detail: ACL tears rarely happen alone. Around half of all ACL injuries also involve damage to the meniscus or the medial collateral ligament, which changes both the treatment timeline and the rehabilitation approach.
What does an ACL injury feel like?
People almost always describe hearing or feeling a “pop” at the moment of injury. Within two hours, the knee swells substantially because the ACL has its own blood supply, and tearing it causes bleeding inside the joint (haemarthrosis). Attempting to walk feels unstable, as though the knee could buckle at any moment.
A common misconception is that if you can still walk, the ACL must be intact. That’s not true. Partial tears and even some complete tears allow limited weight-bearing once the initial swelling settles, but the rotational instability remains. Clinical tests such as the Lachman test and anterior drawer test, performed by a skilled physiotherapist or osteopath, can identify ACL laxity with high accuracy even before imaging confirms the diagnosis.
Does every ACL tear need surgery?
No. This is where individual assessment matters enormously. A 2010 randomised controlled trial in the New England Journal of Medicine (Frobell et al.) compared early surgical reconstruction with structured rehabilitation alone and found no significant difference in patient-reported outcomes at two and five years, with follow-up data now extending to 11 years maintaining those findings. The “rehab first” approach, sometimes called conservative management, works well for people whose daily activities and sport don’t involve high-level pivoting.
For competitive athletes in cutting sports, or for patients who experience persistent giving-way episodes despite thorough rehabilitation, surgical reconstruction followed by a structured return-to-sport programme is usually the better path. The decision isn’t binary. At Costa Health, Daniele Delicati works with each patient to weigh the evidence against their lifestyle, goals, and injury specifics before recommending a course of action.
What does rehabilitation look like?
Whether the route is surgical or conservative, rehabilitation is the critical determinant of outcome. Early-stage rehab focuses on reducing swelling, restoring full knee extension, and reactivating the quadriceps. Progressive strengthening follows, working through open and closed kinetic chain exercises, balance training, and neuromuscular control drills.
Later phases introduce sport-specific movements: cutting, pivoting, jumping, and landing mechanics. Return-to-sport testing should include objective measures such as single-leg hop tests, quadriceps strength symmetry above 90%, and quality-of-movement screening. Rushing this process is the single biggest predictor of re-injury, particularly in the first two years post-injury.
Sports massage plays a supporting role throughout recovery, helping manage muscle guarding in the quadriceps and hamstrings, improving tissue mobility around the surgical site, and reducing compensatory tightness in the hip and calf that develops from altered gait patterns.
When should someone seek urgent care?
Any acute knee injury with a pop, rapid swelling, and an inability to bear weight warrants same-day assessment. If the knee locks or catches, meniscal damage may be involved. Significant bruising tracking down the lower leg can indicate a more complex ligament or vascular injury that needs immediate medical attention.
Costa Health’s team at the Marbella and Riviera del Sol clinics provides thorough knee assessments, rehabilitation planning, and pre- and post-surgical physiotherapy and chiropractic care for ACL injuries. Book a consultation to discuss your injury and recovery options.