Debbie Craig, PhD, AT Program Director of Athletic Training Education Northern Arizona University

1.Spread awareness of MRAs. 1.Meniscal biomechanics with a MRA. 1.Imaging issues with MRA. 1.Clinical diagnosis. 1.Surgical options. 1.Rehabilitation timelines.

Each meniscus is ‘rooted’ down into the tibial plateau at the two ends. If one of these ends tears, the ‘root tear’ is defined as an avulsion injury.

1.Acute 2.Chronic 3.Medial meniscus – ant or post horn 4.Lateral meniscus – ant or post horn

Acute tears are rare injuries. Usually younger athletes Usually combined with multi-ligamentous injuries Kim et al – 2.74% of reported MRAs were acute & were mulit-lig Chronic tears are most common Assoc w degenerative changes in knee S/S and MOI are subtle

Medial root avulsions By far most common – post/med More dire biomech. consequences Lateral root avulsions Less common Less dire than medial due to aid of meniscofemoral ligs, theoretically

During wt bearing, normal menisci function to provide more contact area w the femur and distribute load. The axial load on the menisci places a radial extrusion force, pushing it outward toward its edges. The menisci cannot extrude radially, however, due to the attachmt of the meniscal roots. The root attachmts withstand the circumferential hoop stress with wt bearing.

If a root is torn, the meniscus can no longer handle the circumferential hoop stress, as one of the two attached ends/roots is free. The meniscus then simply shifts out of the way with wt bearing load – i.e. – it extrudes laterally/radially. Notice the joint space heights medial and lateral here - Peterson Fig. 2 here

With MRA, Allaire et al found no difference in peak contact pressure between post-total menisectomy and MRA knees. Marzo et al found an increase in peak contact pressure w MRA: from – 3841 kPa to kPa and a decr contact area A: peak contact stress normal Med Men; B: peak contact stress MRA

X-rays: - to determine presence of jt degen - to determine malalignment - to determine rare bony avulsion MRIs: - gold standard, but high false-neg - up to 1/3 false-neg (Ozkoc et al) - normal meniscal extrusion <3mm - pathologic if >3mm - note if incr signal at root insertion

Post-med MRA Meniscal extrusion

My vert pic hereMy horiz pic here Post Med MRA w Spont osteonecrosis Post Med MRA w Spont osteonecrosis

Q: So, when should we suspect the need to differentiate between a regular meniscus tear and a MRA? A: If there is acute multi-lig injury, the MRI will detect any MRA. A: If athlete presents with joint line pain, consider MRA – esp if a seemingly benign twisting moment was the MOI.

MOI – seemingly benign twisting motion, reports a subtle pop. Joint effusion, though not consistently w lateral MRA. Pain w stair climbing, squatting, any deep knee bending. Bin et al: 95.8% had + McMurrays; 78.1% pain w full forced flexion Lee et al: 57% had + McMurrays; 67% pain w full forced flexion (Thessaly test not studied)

1.Thorough History, Inspection, and Palpation 2.Determine if MOI warrants concern for meniscal root injury 3.Note S/S that show incr pain w deep knee flexion activity 4.Determine presence of joint line pain &/or joint effusion 5.ROM testing is + if passive forced flexion elicits sharp pain 6.Perform Thessaly and McMurrays 7.Perform a Varus Stress Test noting visual extrusion of medial meniscus in ant/med direction (post-med MRA) (Seil et al) 8.Refer if you suspect MRA

Lerer et al found that MRA w medial extrusion may precede degen jt disease, rather than be a result of it. Other studies found the opposite. Spontaneous osteonecrosis may occur with MRAs (Sung et al) My vertical pic here to show spont osteonecrosis

Marzo et al and Gurske- DePerio et al proved that surgical repair restores peak contact pressures to normal. Lateral MRAs with intact meniscofemoral ligs may do well non-surgically. Post-med MRAs need re- fixation surgical repair.

a. Trans-osseous pull-out technique b. Suture anchor technique c. Side to side repair

Non-weight bearing for 6 weeks - exercises to reduce atrophy Avoid excessive flexion at all times Avoid wt bearing knee flexion past 90° RTP at 4 months post-op - continue to avoid deep knee bends

S/S of MRA may be subtle and easily missed. Consequences of non-diagnosis are rapid onset of degenerative joint disease and possible osteo-chondral defects. With a benign twisting MOI, a subtle pop or crack, pain with forced flexion, and a positive McMurrays or Thessaly test – REFER!

Allaire et al. Biomechanical consequences of a tear of the posterior root of the medial meniscus. J Bone Joint Surg Am. 2008;90: Kim et al. Posterior root tear of the medial meniscus in multiple knee ligament injuries. Knee. 2010;17(5): Koenig et al. Meniscal root tears: Diagnosis and Treatment. J Arthrosc Rel Surg. 2009;25(9): Lerer et al. The role of meniscal root pathology and radial meniscal tear in medial meniscal extrusion. Skelet Radiol. 2004;33(10): Marzo et al. Effects of medial meniscus posterior horn avulsion and repair on tibiofemoral contact area and peak contact pressure with clinical implications. Am J Sports Med. 2009;37(1): Ozkoc et al. Radial tears in the root of the posterior horn of the medial meniscus. Knee Surg Sports Traumatol Arthrosc. 2008;16(9): Petersen et al. Posterior root tear of the medial and lateral meniscus. Arch Orthop Trauma Surg. 2013, Dec.;online. Seil et al. Clinical sign to detect root avulsions of the posterior horn of the medical meniscus. Knee Surg Sports Traumatol Arthrosc. 2011;19(12): Sung et al. Meniscal extrusion and spontaneous osteonecrosis with root tear of medial meniscus: Comparison with horizontal tear. J Arthrosc Rel Surg. 2012;29(4):

Debbie Craig, Northern Arizona University,