Anatomy
- The knee joint has two component
- Articulations between the femoral and tibial condyles
- Patellofemoral joint
- It is stabilised by the knee ligaments
- Anterior cruciate ligament prevents anterior translation of the
tibia
- Posterior cruciate ligament prevents posterior translation if the
tibia
- Medial collateral ligament provides valgus stability
- Lateral collateral ligament provides varus stability
- Posteromedial capsule resists external rotation
- Posterolateral capsule resists internal rotation
- The menisci are semi-lunar shaped fibrocartilages
- They increase joint congruence and distribute load across the joint
- They are avascular and heal poorly beyond the peripheries
- Knee movements are complex
- It has dynamic stability
- The joint is not a simple hinge
Clinical features
- The history of any injury suggest which structure may be involved
- Direct varus or valgus forces injure the collateral ligaments
- Indirect forces injure the cruciate ligaments and menisci
- Twisting in flexion can damage the menisci
- Immediate swelling suggests a haemarthrosis
- An audible 'pop' can occur with a cruciate injury
- Mechanical locking is characteristic of a meniscus injury
- Examination should look alignment, wasting, swelling and bruising
- Localised tenderness should be elicited
- The range of passive and active movement should be assessed
Provocation tests
- Anterior and posterior draw test
- Lachman's test
- Pivot shift test
- McMurray's test
Investigation
- Plain radiographs may show avulsion fractures and exclude fractures
around the knee
- MRI is the most useful imaging modality
- Shows extent of soft tissue injuries
Meniscal injuries
- May be traumatic or degenerative
- Classified by position and shape
- Acute peripheral injuries can be repaired
- Chronic central injuries often require arthroscopic partial
menisectomy
- Total menisectomy risk later degenerative changes and should be
avoided
Anterior cruciate injuries
- Acute injuries result in a haemarthrosis
- Results in variable amounts of pain and instability
- Often associated with medial meniscal tear
- Treatment options depend on expectation and life-style of patient
- Options include:
- Physiotherapy
- Early or later cruciate ligament reconstruction
- The most popular grafts are:
- Hamstring graft
- Bone-patella tendon-bone graft
Posterior cruciate injuries
- Usually occurs following dashboard injuries
- Results in knee instability
- Treatment is controversial due to less reliable surgical results
- Surgical reconstruction reserved for multiple ligament injuries
Collateral ligament injuries
- Medial collateral ligament injuries are more common
- Clinical evaluation allows injuries to be graded
- Grade 1 - Local ligament tenderness - no instability
- Grade 2 - Unstable at 20 degrees of flexion - stable in extension
- Grade 3 - Unstable in flexion and extension
- MRI is useful in evaluating extent of injury
- Grade 1 injuries require analgesia and early mobilisation
- Grade 2 injuries require a hinged knee brace
- Grade 3 injuries require surgical repair
Bibliography
Cook J L. The current status of treatment for large meniscal
defects. Clin Orth Relat Res 2005: 435: 88-95
Dowd G S. Reconstruction of the posterior cruciate ligament.
Indication and results. J Bone Joint Surg Br 2004; 86:
480-491.
Koon D, Bassett F. Anterior cruciate ligament rupture.
South Med J 2004; 97: 755-756.
Smith G D, Knutson G, Richardson J B. A clinical
review of cartilage repair techniques. J Bone Joint Surg Br
2005; 87: 445-449. |