The patella runs in a groove in the front part of the femur called the trochlea. It runs through this groove as we bend and extend our knee. The patella engages the trochlea between ten and thirty degrees of bend. Muscles and ligaments help balance the patella within the trochlea.
- Quadriceps tendon—the quadriceps muscle anchors into the patella via the quadriceps tendon.
- Iliotibial band—a large band of tissue of the outer part of our thigh anchors into the tibia. Tightness of this either may lead to pain from our patella not tracking appropriately or may give us pain throughout the course of the band called Iliotibial band syndrome.
- Lateral retinaculum—ligaments on the outer part of the patella help stabilize the kneecap from shifting in an inward or medial direction. Occasionally the retinaculum may become tight and cause our patella to either tilt or sublux in an outward, or lateral, direction.
- Medial patellofemoral ligament—this ligament connects our femur to the inner portion of the patella. This ruptures when we dislocate our patella. In addition, this may stretch either due to injury or from lax tissue and cause a subluxation.
- Patellar tendon—this tendon anchors our patella to the tibia.
Individuals with a tight lateral retinaculum may experience pain without any damage to the cartilage of the patella. The majority of individuals respond to physical therapy, taping, and shoe modification. Those continuing to have symptoms may be a candidate for a lateral release. The images below show images where the lateral retinaculum is cut using a heat probe.
After the lateral retinaculum is identified, the heat probe cuts the tissue. The tethering effect of the retinaculum is eliminated, and will scar at a lengthened position.
Xrays can identify individuals with a patella that subluxes, or tracks, outside the trochlea. This may cause pain, and in some cases, may cause premature cartilage wear on the outer portion of the articulation between the patella and the trochlea. Once again, this usually is treated with physical therapy, taping, and shoe modification. If symptoms persist, surgical options include either tightening of the medial patellofemoral ligament or a tibial tubercle osteotomy.
Patellar dislocations are treated with a period of immobilization followed by physical therapy. Repeated dislocations are treated with a repair of the medial patellofemoral ligament or a tibial tubercle osteotomy. Surgery is indicated if there is a loose body or repeated dislocations. The redislocation rate may be anywhere from 30-50%.
It is common as we age to develop wear either on our patella or trochlea. Activities placing a large amount of stress on these areas include long distance running and jumping sports. Chondromalacia is treated with physical therapy, anti-inflammatories, glucosamine and chondroitin sulfate, corticosteroid injections, and viscosupplementation. Catching, locking, and swelling may indicate a flap which is amenable to surgical treatment (chondroplasty).
The figure below indicates a fissure, or cracking, of the patella that gave this individual pain associated with catching.
This individual underwent a chondroplasty. The cartilage was smoothed using a motorized shaver.
Arthritis refers to the loss of the articular cartilage of the patella and/or trochlea. Treatment is similar to that for patellar chondromalacia. Persistent symptoms are treated with either a tibial tubercle osteotomy of a knee replacement. Note on the image below the complete loss of cartilage on the undersurface of the patella.
TREATMENT OPTIONS FOR PATELLAR INSTABILITY AND/OR TRACKING ISSUES
- LATERAL RELEASE—A lateral release performed in isolation only is indicated for patellar tilt that hasn’t responded to physical therapy, anti-inflammatories, and time.
- MEDIAL PATELLOFEMORAL LIGAMENT REPAIR AND/OR REEFING—The medial patellofemoral ligament connects the femur to the patella. Recurrent dislocations in individuals with healthy cartilage are best treated either with direct repair of the ligament or suture tightening of the ligament. This is done via a small incision. If the tissue is of poor quality, one of our hamstring tendons is used to recreate the ligament. Individuals with normal cartilage and subluxation can be treated with an arthroscopic tightening of the ligament with sutures.
- TIBIAL TUBERCLE OSTEOTOMY—For individuals with patellar tracking issues and significant cartilage damage, a tibial tubercle osteotomy is performed. The bone attachment for the patellar tendon is detached from the tibia (shinbone) and shifted and fixed in place with two screws. This not only assists the tracking and stability of the patella, but also reduces symptoms related to the arthritis.
QUADRICEPS OR PATELLAR TENDON RUPTURE
Rupture of the quadriceps or patellar tendon is treated with urgent surgical repair.