Knee Conditions
From meniscus tears to ACL ruptures and cartilage defects: evidence-based diagnosis and treatment of knee injuries and knee pain.
The knee – the most complex joint in the body
The knee is the largest and most complex joint in the human body, and the most frequently injured in sport. It is stabilised by four main ligaments (ACL, PCL, MCL, LCL), two menisci, the articular cartilage, the patellofemoral joint, and the surrounding musculature. Injuries to any of these structures can cause significant pain and functional limitation – but not all of them require surgery.
Evidence-based treatment means: the right therapy for the right patient at the right time. For degenerative meniscus tears, randomised controlled trials (METEOR, FIDELITY) have shown that structured physiotherapy is equally effective as arthroscopic surgery. For traumatic ACL ruptures in young athletes, surgical reconstruction is well-supported by evidence. The decision is always individual.
- Meniscus tears (traumatic and degenerative)
- Anterior cruciate ligament (ACL) rupture
- Cartilage defects (chondral and osteochondral)
- Patellofemoral instability (patellar dislocation)
- Jumper's knee (patellar tendinopathy)
- Plica syndrome
- Fractures around the knee joint
Meniscus injuries
The menisci are C-shaped fibrocartilage structures that distribute load, stabilise the knee and protect the articular cartilage. Meniscus tears are the most common knee injury. Traumatic tears in young patients (bucket-handle tears, radial tears) often require surgical treatment – repair is preferred over resection to preserve meniscus tissue and reduce the risk of later arthritis. Degenerative tears in middle-aged patients are best treated with structured physiotherapy as the first-line approach, based on Level 1 evidence.
The principle is: preserve as much meniscus as possible. Every millimetre of resected meniscus increases the risk of future osteoarthritis. Meniscus repair has become the preferred technique for repairable tears in the vascular zone.
ACL rupture
The anterior cruciate ligament (ACL) is the primary restraint against anterior tibial translation and rotational instability. ACL ruptures are common in pivoting sports (football, skiing, basketball). In young, active patients who want to return to pivoting sport, ACL reconstruction is the standard of care. The hamstring tendon autograft and the bone-patellar tendon-bone autograft are the most commonly used grafts, with comparable long-term outcomes. Return to sport is criteria-based – not calendar-based – and typically takes 9 months.
Cartilage defects
Articular cartilage has limited self-healing capacity. Focal cartilage defects in young patients can be treated with bone marrow stimulation (microfracture, AMIC) for defects under 2 cm², or with matrix-associated autologous chondrocyte implantation (MACI) for larger defects. These procedures aim to restore a functional cartilage surface and delay or prevent the progression to osteoarthritis.
Diagnosis
Clinical examination remains the cornerstone of knee diagnosis. The Lachman test (sensitivity 85%) and pivot shift test are standard for ACL assessment. McMurray's test and joint line tenderness assess the menisci. The MRI is the imaging of choice for soft tissue structures – but findings must always be interpreted in the clinical context. A degenerative meniscus finding on MRI in a 50-year-old does not automatically indicate surgery.
Weight-bearing X-rays in standing position are essential for assessing joint space and alignment. CT is used for fracture assessment and preoperative planning. Ultrasound is useful for dynamic assessment of tendons and bursae.
Frequently asked questions
Does every meniscus tear need surgery?
No. Degenerative meniscus tears in middle-aged patients should be treated with structured physiotherapy first. Randomised trials (METEOR, FIDELITY) show no benefit of arthroscopic surgery over physiotherapy for degenerative tears. Traumatic tears in young patients, especially bucket-handle tears causing mechanical symptoms, often do require surgery.
How long does ACL rehabilitation take?
Return to pivoting sport typically takes 9 months with a criteria-based protocol (strength symmetry ≥90%, hop tests, psychological readiness). Returning earlier significantly increases re-rupture risk. The rehabilitation plan is discussed in detail before surgery.
Can cartilage grow back?
Articular cartilage has very limited self-healing capacity. Modern surgical techniques (microfracture, AMIC, MACI) can restore a functional cartilage surface, but the regenerated tissue is not identical to native hyaline cartilage. Early treatment of focal defects gives the best results.
References & Evidence
- Katz JN, Brophy RH, Chaisson CE, et al. Surgery versus physical therapy for a meniscal tear and osteoarthritis. N Engl J Med 2013;368:1675–1684. PMID: 23614526
- Sihvonen R, Paavola M, Malmivaara A, et al. Arthroscopic partial meniscectomy versus sham surgery for a degenerative meniscal tear. N Engl J Med 2013;369:2515–2524. PMID: 24369076
- Spindler KP, Wright RW. Anterior cruciate ligament tear. N Engl J Med 2008;359:2135–2142. PMID: 19005200
- Filardo G, Andriolo L, Soler F, et al. Treatment of unstable knee osteochondritis dissecans in the young adult: results and limitations of surgical strategies – the advantages of allografts to address an osteochondral challenge. Knee Surg Sports Traumatol Arthrosc 2019;27:1726–1738. PMID: 30426163
- Frobell RB, Roos EM, Roos HP, Ranstam J, Lohmander LS. A randomized trial of treatment for acute anterior cruciate ligament tears. N Engl J Med 2010;363:331–342. PMID: 20660401
- Mithoefer K, McAdams T, Williams RJ, Kreuz PC, Mandelbaum BR. Clinical efficacy of the microfracture technique for articular cartilage repair in the knee: an evidence-based systematic analysis. Am J Sports Med 2009;37:2053–2063. PMID: 19251676
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