Patellofemoral Partial Knee Replacement
Resurfacing the compartment behind the kneecap alone: the narrowest form of partial knee replacement and the one selection matters most for.
The short answer
Some knees wear out only where the kneecap glides on the thighbone. Resurfacing that surface alone is possible, and it is the most selective of the three partial replacements, because pain at the front of the knee has several possible sources.
How partial knee replacement works
This one-minute patient-education animation from Stryker shows how a partial knee replacement resurfaces only the worn compartment while the healthy parts of the joint stay. It is a general illustration, not a recording of any specific operation; the safety information at the end is Stryker’s.
The compartment behind the kneecap
The kneecap glides in a groove at the end of the thighbone. When the cartilage on those two surfaces wears out and the rest of the knee is healthy, the arthritis is called patellofemoral.
The pattern is typical: pain at the front of the knee, worse on stairs, hills, and standing up after sitting, rather than the deep ache of walking on level ground.
Why selection is the whole conversation
Pain at the front of the knee has many possible causes, and only some of them are arthritis of this compartment. Tendon problems, tracking problems, referred pain from the hip, and early arthritis elsewhere in the knee can all present the same way.
That is why this operation is only discussed after imaging and examination agree on the source. Resurfacing the wrong compartment does not relieve pain, and it is a poor trade.
What it involves, and what it leaves alone
The operation resurfaces the groove and the back of the kneecap and leaves the inner compartment, the outer compartment, and the ligaments untouched. Bone and ligament are preserved for the parts of the knee that are still working.
A total knee replacement remains the option that treats everything at once. When wear extends beyond the kneecap compartment, that is usually the more predictable plan.
What to try before either operation
Pain at the front of the knee often responds to non-surgical care, and that is where the plan usually starts. Physical therapy aimed at the quadriceps and hip muscles, activity adjustment, anti-inflammatory medication where it is safe for you, and selected injections are all reasonable first steps.
For this compartment in particular, therapy is worth a genuine trial before an operation is discussed. Deciding to wait is a supported choice.
Risks and the possibility of a later operation
This carries the usual replacement risks: infection, blood clots, stiffness, and loosening or wear that needs further surgery. It also carries the partial-replacement risk that arthritis progresses in the compartments left alone.
When that happens, conversion to a total knee replacement is generally possible. That is a second operation with its own recovery, and it belongs in the first conversation.
Use the consultation to make the decision clearer.
- Is my pain coming from the kneecap compartment specifically?
- Does my imaging show the other compartments are healthy?
- What else could be causing pain at the front of my knee?
- Would a total knee be more predictable in my case?
- What would conversion to a total knee involve later?
Sources and further reading
- Unicompartmental (Partial) Knee ReplacementAmerican Academy of Orthopaedic Surgeons
- Total Versus Partial Joint ReplacementAmerican Academy of Orthopaedic Surgeons
- The clinical and cost-effectiveness of total versus partial knee replacement (TOPKAT): 5-year outcomes of a randomised controlled trialThe Lancet (Beard et al., 2019)
- Optimal usage of unicompartmental knee arthroplasty: a study of 41,986 cases from the National Joint Registry for England and WalesThe Bone & Joint Journal (Liddle et al., 2015)
- Lateral Unicompartmental Knee Arthroplasty (textbook chapter co-authored by Dr. Patel)Essentials of Cemented Knee Arthroplasty, Springer, 2022