Medial Parapatellar Approach to Knee

What it exposes. The medial parapatellar approach gives direct, circumferential access to the entire knee - the distal femur, the proximal tibia, both menisci and cruciates, and the patellofemoral joint. It is the most commonly performed surgical approach to any joint in orthopaedic surgery: total knee arthroplasty (TKA) is among the highest-volume elective procedures worldwide (over 1 million per year in the United States alone and rising in every major registry), and the medial parapatellar approach is used in roughly 80-90% of primary TKAs. It is therefore essential for every orthopaedic surgeon and is a core topic across advanced orthopaedic practice and DNB/MS fellowships. Why medial rather than lateral. The medial route is strongly preferred for four reasons. First, patellar blood supply: the lateral superior genicular artery is the dominant contributor to the patellar anastomotic ring, and a medial approach preserves it while a lateral approach risks patellar avascular necrosis. Second, patellar tracking biomechanics: the patella naturally tracks slightly lateral (the Q-angle), the lateral retinaculum is stronger than the medial, and working from the medial side allows a controlled lateral release if needed - the lateral side cannot be balanced by releasing medially. Third, deformity correction: most arthritic knees drift into varus, and the medial approach allows release of contracted structures and easier balancing. Fourth, surgeon positioning: standing on the lateral side gives ergonomic access to both femur and tibia. Historical context. Von Langenbeck is credited with the medial parapatellar exposure in the 1860s-1870s; the technique was refined through the development of modern condylar TKA (Gunston, Freeman, Insall) in the 1950s-1970s, standardised by John Insall and the Hospital for Special Surgery group in the 1980s, and joined by muscle-sparing alternatives (subvastus, midvastus) in the 1990s-2000s. Modern evidence shows that the quality of repair and component balance matter more than which approach is chosen.

Position & landmarks. Supine on a standard table with a lateral leg holder (most common) or leg post to hold flexion - pad lateral to the fibular head to avoid common peroneal nerve compression. Lower the foot of bed (or use a radiolucent triangle) so the knee can flex to 90° for tibial preparation. Apply an upper-thigh tourniquet as proximal as possible, typically 250-300 mmHg (or systolic plus 100-150 mmHg), tested before draping. Prep and drape circumferentially from mid-thigh to ankle, then perform the time-out. Palpate and mark the midline over the patella, the medial border of the patella, the VMO belly proximally, and the tibial tubercle distally - the line of the incision. Previous incisions. A previous vertical midline scar is reused. With multiple scars, use the most lateral viable incision to preserve the medial skin blood supply. A previous vertical lateral incision is a relative contraindication to a medial approach because of skin-flap vascular compromise - consider plastic surgical input.

Work from skin to a balanced, cemented knee in a sequence built around the extensor mechanism: a midline incision, a medial parapatellar arthrotomy that stays anterior to the MCL, eversion of the patella, then joint preparation, trialling and a meticulous layered closure. Every step is designed to protect the patellar tendon, the patellar blood supply and the VMO.

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Structures at risk, by layer

Extensile options for the difficult knee

Decision algorithm. Cannot evert the patella - complete the standard releases first (suprapatellar pouch, lateral gutter, posterior capsule) and externally rotate the tibia. Still inadequate - perform a quadriceps snip. Revision with a well-fixed patella or an ankylosed knee that will not expose - proceed to a tibial tubercle osteotomy. Only a truly ankylosed knee needing massive releases warrants a V-Y quadricepsplasty. Approach-specific complications

• Primary total knee replacement and cemented TKA - the principal operations done through this exposure, cruciate-retaining or posterior-stabilised.
• TKA for valgus deformity - the medial approach allows staged lateral releases for balancing.
• Management of the stiff total knee arthroplasty - arthrolysis and revision through the same extensile route.
• Revision TKA - using the quadriceps snip, tibial tubercle osteotomy or V-Y quadricepsplasty as exposure demands.
• Knee synovectomy for inflammatory arthropathy.
• Cartilage restoration - autologous chondrocyte implantation, osteochondral allograft and osteochondral autograft (OATS) - through a medial parapatellar arthrotomy in selected younger patients.
• Constrained / hinged total knee replacement for instability or revision with ligament deficiency.

Guidelines, registries and global practice - The medial parapatellar approach is the predominant approach for primary TKA across all major registries (NJR, AJRR, AOANJRR, Swedish Knee Arthroplasty Register), with cumulative 15-year revision around 8-12% - broadly comparable to total hip arthroplasty.

• Leading revision indications are aseptic loosening, infection and instability; registries consistently show no meaningful difference in revision rate between medial parapatellar, subvastus and midvastus approaches.
• The approach is fully compatible with enhanced recovery (multimodal analgesia, local infiltration analgesia, early mobilisation, tourniquet minimisation).

Antibiotic prophylaxis. A first- or second-generation cephalosporin (cefazolin 2 g IV) at induction is standard worldwide; vancomycin (weight-based) or teicoplanin if there is significant beta-lactam allergy or known MRSA colonisation. Redose for prolonged surgery or major blood loss; routine postoperative antibiotics are not recommended.