Meniscal detachment

This term can be used to describe a high energy injury to the meniscus, usually in young patients. During the act of ligament rupture there is very rapid dissipation of energy with instantaneous displacement of the femur on the tibia "snap":-

This can cause severe damage to the meniscii either wrenching them from their attachment ("peripheral detachment") or by splitting off a large "bucket handle" segment. This is different to the common degenerative tear where a meniscus has gradually become weaker and weaker to finally fail following a trivial injury ("the straw that broke the Camel's back").

In young patients these injuries can be repaired reducing the risk of early osteoarthritis. It is important that they are recognised early to increase the success rate for repair. Meniscal detachment can accompany any pattern of ligament rupture :-

Ligament Injury	Rate of Meniscal detachment
MCL	??
ACL	36% Medial Tear 47% Lateral Tear
PCL	??
PLC	??
Multiligament injury	2.7 % Medial Posterior Root Avulsion

Hx	Significant force Significant twisting injury Immediate pain +- "pop" Immediate swelling with haemarthrosis
LOOK	True locked knee
FEEL	Joint line tenderness Associate ligament injury causing localised tenderness
MOVE	Reduced active movement due to pain True locked knee : Passive flexion deformity, the knee will flex reasonably normally but cannot be straightened out. Exclude combined MCL + Meniscus Valgus force tests Exclude combined ACL + Meniscus AP force test the ACL ("Lachman's test", "Anterior draw test") IR subluxation/reduction tests ACL ("Pivot shift test")
XRAYS	AP and Lateral views Usually normal Exclude combination injuries ACL: Segond fracture, Tibial spine avulsion MCL: Medial opening
MRI	This is the principle reason for MRI scans in ACL rupture - not to confirm the ACL rupture which is usually clinically obvious

Treatment is usually dictated by the ligamentous injury. For an isolated "bucket handle tear" with a true locked knee :-

Meniscal detachments are amendable to repair with sutures if seen early. Once the femur has rolled over the meniscal fragment for a week or two it is too distorted to fix back in position. Additionally the longer this injury is left the poorer the healing capacity when the two parts are reunited.

The blood supply to the meniscus is normally poor (hence degeneration with age) and failure of meniscal healing leads to failure of meniscal suturing in 10-30 percent of cases. Even with this relatively high rate of failure repair is recommended because the long term benefit for the successful cases is high, and the morbidity from a second arthroscopy and resection of the failed meniscal repairs is low.

As an isolated treatment meniscal repair should be protected from shear forces for 8 weeks. This means avoiding flexion beyond 100 degrees and excessive load bearing under flexion. Braces can be used for patients who find it difficult to comply.

When repaired as part of a ligament reconstruction the meniscus can usually be ignored as patients tend to protect the knee for the first 6-8 weeks and the risk of disrupting the meniscal repair is low.