Working Diagnosis:
Lateral meniscus subluxation with a longitudinal tear.

Treatment:
The patient elected for surgical repair and underwent right knee arthroscopy.
The lateral meniscus was sutured on both sides of the popliteal hiatus and could no longer be moved, indicative of a stable repair.

Outcome:
Four weeks post-op, the patient was improving. He was having minimal pain and doing well with his therapy. His right quadriceps was slightly weaker compared to the left. He continued to wear a post-op brace with activity and took it off when in a controlled situation. At 8 weeks post-op, he started doing lower body workouts, and at three months post-op, he returned to athletic activities.

Author's Comments:
The lateral and medial meniscus are fibrocartilaginous structures between the femur and the tibia. The lateral meniscus is more mobile than the medial meniscus due to its lack of attachment to the capsular ligament posterolaterally. This lack of attachment is due to the presence of the popliteal tendon entering the knee. This makes the lateral meniscus more prone to subluxation.
Case Photo #4

Editor's Comments:
Meniscal pathology of the knee can be difficult to diagnose and may mimic other conditions including a cartilage fissure, osteochondral defect, or fracture. Helpful meniscal tear physical exam maneuvers include the McMurray's test, Apley grind adn the Thessaly's test. In one study, Thessaly's test showed 91 percent sensitivity adn 97 percent specificity for meniscus tears, outperforming the other two tests.
Meniscal injuries that result in subluxation are important to recognize as the subluxation leads to significant stress in the underlying articular cartilage. This results in rapid progression of cartilage degeneration.

References:
Ahn JH, Lee SH, Kim KI, Nam J. Arthroscopic meniscus repair for recurrent subluxation of the lateral meniscus. Knee Surg Sports Traumatol Arthrosc. 2018;26(3):787-792. doi:10.1007/s00167-017-4420-2.
Ockert B et al. Value of the clinical examination in suspected meniscal injuries. A meta-analysis. Unfallchirurg. 2010 April;113(4):293-9.
Choi YR, Kim JH, Chung JH, et al. The association between meniscal subluxation and cartilage degeneration. Eur J Orthop Surg Traumatol. 2014 Jan;24(1):79-84.
Gokkus K, Atmaca H, Ugur L, Ozkan A, Aydin AT. The relationship between medial meniscal subluxation and stress distribution pattern of the knee joint: Finite element analysis. J Orthop Sci. 2016 Jan;21(1):32-7.

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