Anterior Knee Pain Syndrome
Dr. Renny Uppal, MD
What is anterior knee pain?
Pain around the front of the knee is often referred to as patellofemoral pain. This pain may be caused by soft cartilage under the kneecap (patella), abnormal tracking (or alignment) of the kneecap, an irritation of the soft tissues around the front of the knee, or referred pain from other areas such as the back or hip. It is one of the most common causes of knee pain in young active patients. Symptoms typically wax and wane for long periods of time, and are worse with squatting, stairs, and prolonged sitting. Patients may or may not have a specific history of trauma.
The knee cap is a flat triangular bone about two inches wide. It is just one of several parts that make up the knee joint. Other structures are the muscles, tendons, ligaments and cartilage. The kneecap plays a special role: it protects the knee joint and also gives your muscles the extra leverage they need to straighten the leg more efficiently. The knee cap (patella) is a flat triangular bone about two inches wide. It is just one of several parts that make up the knee joint. Other parts of the knee are muscles, tendons, ligaments and cartilage. The kneecap plays a special role: it protects the knee joint and also gives your muscles the extra leverage they need to straighten the leg more efficiently. Quadriceps muscles at the front of your thigh hold the kneecap against the thigh bone and help straighten the leg. Other muscles on the inside of your thigh (adductors), back of your thigh (hamstrings), and back of your shin (calves) help the quadriceps move your leg. The kneecap (patella) anchors your quadriceps muscles as they contract, and protects the bones and other tissues underneath it. Retinacula are fibrous bands on the sides of the kneecap. They help hold the kneecap in place. The patellar tendon is a fibrous cord that connects the patella to the shinbone.
Patellar Malalignment (Subluxation)
Some patellofemoral pain is caused because the kneecap is abnormally aligned. This can cause abnormal stresses to the supporting tissue around the kneecap, and possible wear to the cartilage under the kneecap. Kneecap malalignment is most commonly seen in young women whose kneecap tends to pull or tilt to the outside. In severe cases, the kneecap may actually dislocate. Anatomic variations such as a tight fibrous band (lateral retinaculum) attached to the outside of the kneecap, and an abnormal attachment of the patellar tendon on the shinbone, are often seen in these patients. Other contributing factors include weak thigh muscles (particularly the vastus medialis obliquus or VMO), a knock knee deformity, and flat feet.
Treatment is initially directed at decreasing symptoms and improving function. Symptomatic treatment with icing, anti-inflammatory medication, and activity modification is encouraged. Physical therapy is helpful to correcting underlying muscle weakness (VMO) and improving overall flexibility. Knee braces which help hold the kneecap in proper alignment, and arch supports to correct flat feet, may be beneficial. A small percentage of patients with debilitating symptoms who do not respond to conservative treatment may be candidates for surgery.
Surgical treatment usually involves an arthroscopic procedure (lateral release) to release the tight tissue that tethers the kneecap to the outside of the knee. Occasionally, a larger open operation is needed to move the attachment site of the patellar tendon. This involves cutting a small portion of the shinbone and moving it over to correct the maltracking. Both of these procedures are performed on an outpatient basis.
Transferring the patellar tendon establishes a balanced pull from the quadriceps muscle to the lower leg. Part of the tendon and the underlying bone are moved to a new location and anchored by screws. This surgery is done through an open skin incision. A lateral release is a surgical procedure performed through small nicks in the skin. By cutting the retinaculum, the pull on the kneecap is reduced. The kneecap is then able to move into its proper place and pressure underneath the kneecap is usually reduced.
Chondromalacia refers to the softening and breakdown of the lining cartilage under the kneecap. This actually represents an early stage of arthritis. It may be caused by trauma, overuse, or malalignment. Many times the exact reason people develop this condition is unknown, and genetic factors may play a role. Conservative treatment is similar to that for patellar malalignment. In addition, oral supplements such as glucosamine and chondroitin sulfate may slow the cartilage breakdown and provide symptomatic relief. If swelling or “fluid on the knee” develops, removing the fluid and injecting a steroid into the joint is helpful. Newer injections that provide a lubricant to the joint are also available. If conservative treatment fails to decrease symptoms, surgery may be indicated. This usually involves an arthroscopic surgery to remove loose cartilage and smooth the undersurface of the kneecap. While this does not put normal cartilage back into the damaged areas, it can be quite helpful in providing pain relief and better function for many years.
Patellar tendonitis (“jumper’s knee”) causes pain below the kneecap and is usually caused by inflammation and degeneration of the tendon that connects the knee cap to the shinbone. Pain at the top of the knee cap is usually a result of quadriceps tendonitis and is often seen in the older athlete. Both conditions usually occur from repetitive activities and overuse. Pain is usually located directly over the involved tendon. Symptoms are worse at the beginning of activity, may improve once you are warmed up, but return after cooling down. Physical therapy for instruction in stretching and strengthening exercises is beneficial. Various therapy modalities such as ultrasound, iontophoresis, and anodyne treatments directly over the painful area help decrease pain and inflammation. Icing directly after activity will also help decrease symptoms. Relative rest and activity modifications are often the best treatment. You must try to avoid activities that cause pain, while staying active with less stressful (and painful) exercise to maintain fitness.
Plica Bands are elastic fibers inside the knee that usually run along the side of the kneecap. These bands usually disappear early on in childhood. However, in some people the bands never go away.
These bands usually do not cause any problems and most people do not even notice them. Occasionally the bands become irritated and inflamed; this may cause them to become thickened and possibly painful. They will sometimes cause “popping” or “snapping” of the knee.
Symptoms usually respond to rest, icing, anti-inflammatory medication, and physical therapy. Occasionally a steroid injection may be used to reduce swelling. In rare cases the symptoms persist or recur, requiring an arthroscopic surgery to remove the plica band.