Knee · Cartilage
MACI cartilage implantation — patellofemoral
Kneecap (Patella) or Trochlea Cartilage Defect — Matrix-Induced Autologous Chondrocyte Implantation
The condition
Articular cartilage covers the back of the kneecap (patella) and the groove it glides in (trochlea). A cartilage defect there—from injury, kneecap dislocation, or wear—heals poorly and causes pain at the front of the knee with stairs, squatting, and sitting, plus swelling and grinding.
The surgery
MACI repairs the defect with your own cartilage cells over two surgeries, both typically outpatient. Stage 1 (biopsy): a small sample of healthy cartilage is taken with a camera, and your cells are grown in a lab. Stage 2 (implant): usually 4–6 weeks later, the cells, on a thin membrane, are glued into the defect through an open incision. The bump on the shin bone may also be shifted (TTO). The final plan is determined during surgery.
Recovery at a glance
- After Stage 1
- Quick recovery: walking as tolerated (crutches for a few days if needed); desk work and daily activities within ~1 week.
- Weight-bearing
- After Stage 2: weight as tolerated with crutches and the brace locked straight, full by 6 weeks (with a TTO: touch-down for ~6 weeks). The brace comes off at ~6 weeks.
- Motion
- A motion (CPM) machine is used daily for 6 weeks (if no TTO). Bending advances slowly to protect the implant: 30° for 2 weeks, 90° by 4 weeks, 125° by 6 weeks; full by ~8 weeks.
- Daily life
- Desk work often within 2–4 weeks. Deep squats and lunges are avoided for months; cycling and swimming from ~3 months. No driving while taking narcotic pain medication.
- Running & sports
- The new cartilage matures over 1–2 years. Jogging begins at 6–9 months, once cleared. Impact, cutting, and contact sports no sooner than 12 months; full release typically 12–18 months.
A general guide. Your restrictions and timeline may change based on what is found and done at surgery.
Risks & benefits
Benefits: Most patients have less pain and better function, with lasting results in long-term studies. Risks are uncommon and include infection, blood clots, the implant not bonding or coming loose, overgrowth of the new cartilage (which may need trimming), a reaction to the implant materials, injury to nearby structures (such as nerves, blood vessels, or cartilage), stiffness, persistent pain, and the need for further surgery. These will be reviewed with you in detail before surgery.
Patient Surgical Information
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Before & after every surgery