Have you ever experienced a sudden, sharp pain in your knee and wondered what exactly went wrong? Or have you watched an athlete collapse on the field, clutching their knee, and felt sympathy for their plight? Knee injuries, particularly to the anterior cruciate ligament (ACL), can be devastating, leaving individuals sidelined and unsure of their recovery prospects.
Knee injuries are among the most common musculoskeletal complaints, affecting athletes and non-athletes. The ACL, one of the key ligaments stabilising the knee joint, is especially vulnerable during high-impact sports or sudden, awkward movements.
Understanding the mechanisms of ACL and knee injuries is critical to effective management and recovery. Whether you’re an athlete trying to regain your game or everyday mobility, knowing the right steps can make all the difference.
ACL injuries: Assessment
ACL injuries often occur with a non-contact deceleration or change of direction, a fixed foot, and a valgus (knock-knee) twisting injury. Patients typically report hearing or feeling a "pop" in their knee, followed by immediate pain and swelling. They may also experience a feeling of instability or "giving way" of the knee.
1. Detailed history
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Mechanism of injury: How did the injury occur (e.g., twisting, direct blow, landing awkwardly)?
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Sound/feeling: Did the patient hear a "pop" or feel a "shift"?
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Weight-bearing ability: Could they walk immediately after the injury?
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Pain and swelling: Onset and severity.
- "Giving way" episodes: Frequency and activities that provoke them.
2. Physical examination
This can be challenging in the acute phase due to pain and swelling, and may need to be repeated after a few days once swelling subsides. Key tests include:
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Lachman test: Considered the most accurate test for ACL tears. The knee is flexed to 15-20 degrees, and the examiner stabilises the femur while applying an anterior force to the tibia. Excessive anterior translation of the tibia with a "soft" endpoint indicates a positive test.
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Anterior drawer test: The knee is flexed to 90 degrees, and the tibia is pulled forward. Excessive anterior movement compared to the uninjured side may indicate an ACL disruption. This test is less accurate than the Lachman test in the acute phase.
- Pivot shift test: This test is highly specific for an ACL rupture and reproduces the "giving way" sensation. It involves applying valgus and internal rotation forces to the leg while flexing the knee, looking for a sudden subluxation and reduction of the tibia.
3. Imaging
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X-rays: Primarily used to rule out fractures of the bones around the knee (femoral condyles, tibial plateau, patella) and avulsion injuries.
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Magnetic resonance imaging (MRI): The gold standard for confirming ACL diagnosis and assessing for associated injuries such as meniscal tears, collateral ligament tears, and bone contusions.
- Ultrasound: Can be used to check for injuries in ligaments, tendons, and muscles around the knee.
4. ACL injury grading
ACL injuries are graded based on the severity of the damage:
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Grade I: A few fibres are damaged or stretched. The ligament is still intact. Often referred to as a sprain.
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Grade II: More fibres are torn, but the ligament is partially intact. It may be referred to as a severe sprain.
- Grade III: The ligament is completely torn into two pieces, leading to instability of the knee joint.
ACL injuries: Treatment
Treatment options depend on factors like the grade of the tear, the patient's age, activity level, and presence of other knee injuries.
Non-surgical treatment
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RICE therapy (rest, ice, compression, and elevation) is the immediate first-line treatment to manage pain and swelling.
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Knee bracing: Provides external support to limit excessive movement and stabilise the knee, especially during low-impact activities.
- Physical therapy: Focuses on restoring knee strength, stability, and mobility. Exercises include strengthening the quadriceps and hamstrings, balance and coordination training, and core/gluteal strengthening. Preoperative rehabilitation can improve function before surgery.
Non-surgical treatment may be considered for all ACL tears, with new evidence that they may heal. A three month trial of conservative management is recommended for everyone post ACL rupture. However, those that continue to experience recurrent knee instability may require operative management.
Other common knee injuries
Besides ACL tears, the knee is susceptible to various other injuries:
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Meniscus tears: Tears in the C-shaped cartilage that cushions the knee joint. Often caused by twisting motions or impact, and can lead to clicking, catching, or locking of the knee.
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Medial collateral ligament (MCL) injuries: Tears or sprains of the ligament on the inside of the knee, usually from a valgus (sideways) force. Treatment often involves RICE, bracing, and rehabilitation, with surgery typically reserved for severe cases or multi-ligament injuries.
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Lateral collateral ligament (LCL) injuries: Tears or sprains of the ligament on the outside of the knee, usually from a varus (sideways) force. Less common than MCL injuries.
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Posterior cruciate ligament (PCL) injuries: Tears of the ligament at the back of the knee, often from a direct blow to the front of a bent knee (e.g., dashboard injury). Non-surgical treatment is often sufficient for isolated PCL tears.
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Patellar tendonitis (jumper's knee): Inflammation of the patellar tendon, common in athletes who jump frequently.
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Patellofemoral pain syndrome (runner's knee): Pain around the kneecap, often due to imbalances or overuse.
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Fractures: Breaks in the bones around the knee, such as the patella, femur, or tibia, often due to high-impact trauma.
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Dislocations: When the bones of the knee are forced out of alignment.
- Bursitis: Inflammation of the fluid-filled sacs (bursae) that cushion the knee joint.
Final thoughts
Proper assessment, including detailed history, physical examination, and appropriate imaging, is essential for accurate diagnosis of knee injuries.
Treatment plans are highly individualised and aim to restore function, reduce pain, and prevent long-term complications.
Book an appointment with one of our highly qualified Mulgrave physiotherapists at Enhance Physio before starting a rehabilitation program. We can advise you on the best course of action for your condition.
