Knee injuries Flashcards
what is the primary function of the Anterior cruciate ligament (ACL)
important stabiliser of the knee, limits anterior translation of the tibia relative to the femur
also contributes to knee rotational stability
what is the typical mechanism of injury for an ACL tear?
athlete with a history of twisting the knee whilst weight bearing
majority occur without contact and result from landing from a jump - athlete unable to continue after injury
ACL clinical features
rapid joint swelling
significant pain
instability - leg ‘giving way’
why is there rapid joint swelling in an ACL tear?
the ACL is highly vascular and damage causes haemarthrosis - apparent within 15-30 mins
what are the clinical tests that can identify potential ACL damage?
Lachman Test
Anterior Draw Test
what is the Lachman Test?
place knee at 30 degrees flexion with one hand stabilising femur and one pulling tibia forward to assess the amount of anterior movement of tibia compared to femur - examine both knees for comparison
what is the anterior draw test?
flex knee to 90 degrees, place thumbs on joint line and index fingers on hamstring tendons posteriorly. apply force anteriorly to demonstrate any tibial excursion - examine both knees for comparison
what are dome DDx for ACL tear?
fracture
meniscal tear
collateral ligament tear
quadriceps or patellar ligament tear
what investigations are done for a ?ACL tear?
plain film radiograph - AP and lateral - to exclude bony injuries, joint effusion or a lipohaemarthrosis
MRI - gold standard for diagnosis and also pick up associated meniscal tears - 50% ACL tears also have meniscal tear (lateral meniscus most common)
management of ACL rupture
immediate - RICE
conservative or surgical - depending on suitability of patient for surgery and current activity levels
conservative treatment for ACL rupture
rehab - strength training of quadriceps to stabilise knee
canvas knee splint for comfort
surgical repair of an ACL rupture
use of a tendon as an artificial graft, following a period of prehabilitation (physiotherapy input for a few months before surgery)
complications of ACL rupture and ACL reconstruction
post-traumatic osteoarthritis
what is the main function of the posterior cruciate ligament (PCL)?
primary restraint to posterior tibial translation and prevent hyeprflexion of the knee
how to PCL tears occur?
usually occur in high-energy trauma - direct blow to proximal tibia during RTA
less common - low energy trauma where knee is hyper-flexed with a plantar-flexed foot
clinical features of a PCL tear
immediate posterior knee pain
instability of the joint and a positive posterior draw test
imaging for PCL tear
gold standard is MRI
how are PCL tears managed
treated conservatively
knee brace and physiotherapy
may require surgery if patient continues to be symptomatic and has recurrent instability
association with other injuries may require urgent surgical treatment
what is the most common injured ligament of the knee?
medial collateral ligament (MCL)
what is the main function of the MCL?
act as a valgus stabiliser
how is the MCL most commonly injured
when external rotational forces are applied to the lateral knee
how are MCL injures graded?
Grade I - mild injury, minimally torn fibres, no loss of MCL integrity
Grade II - moderate injury, incomplete tear and increased laxity of MCL
Grade III - severe injury, complete tear and gross laxity of MCL
clinical features of a MCL tear
some patients report hearing a ‘pop’ with immediate medial joint line pain
swelling follows after a few hours (unless haemarthrosis then there will be swelling within minutes)
on examination - increased laxity when testing MCL via valgus stress test
may be unable to weight-bear
DDx for MCL tear
fracture
meniscal injury
collateral ligament tears
investigations for ?MCL tear
plain radiograph film
gold standard MRI - delineating exact extent and grade of tear
management of MCL tear
grade dependent
management of MCL tear - grade 1
RICE, analgesia, strength training as tolerated should be incorporated with aim to return to full exercise in ~6 weeks
management of MCL tear - grade 2
analgesia with a knee brace and weight-bearing/strength training as tolerated, return to full exercise ~12 weeks
management of MCL tear - grade 3
analgesia with knee brace and crutches, associated distal avulsion then surgery is considered
aim to return to full exercise ~12 weeks
complications of MCL tear
instability in joint
damage to saphenous nerve
where are the menisci located and what is their function?
C-shaped fibrocartilage found in the knee joint - rest on tibial plateau and have 2 main functions 1. shock-absorbers 2. increase articulating surface area
differences between the medical and lateral meniscus
medial meniscus - more circular, attached to MCL
lateral meniscus - not attached to LCL
what is the most common cause of meniscal tears?
trauma-related injuries - young patient who has twisted their knee whilst it is flexed and weight-bearing
degenerative disease
