Knee pain that occurs when squatting deeply or kneeling is often referred to as anterior knee pain. This discomfort signals that the joint is under abnormal stress or that a soft tissue structure is being irritated by the movement itself. Understanding the source of this pain involves looking closely at the mechanics of the knee joint during these specific, high-load positions. Most cases stem from mechanical imbalances or overuse injuries that are treatable.
Understanding the Biomechanics of Pain
The primary source of pain during deep knee flexion is often the patellofemoral joint, which is the articulation between the kneecap (patella) and the thigh bone (femur). When the knee bends, the patella tracks within a groove on the femur, and the forces acting on this joint increase dramatically. Compressive force is the pressure load on the cartilage underneath the kneecap, and it is the key mechanical factor in this type of pain.
During the act of lowering into a deep squat, the patellofemoral compressive force can spike to several times your body weight, sometimes reaching an estimated 3.4 to 9 times body weight during the active descent. This pressure is created by the tension in the quadriceps muscle pulling the kneecap tightly against the femur. The pressure is highest when the knee is flexed between 60 and 90 degrees, which is a common range for many daily activities.
The health of the patellofemoral joint relies on proper patellar tracking, meaning the kneecap must glide smoothly within the femoral groove. If the muscles surrounding the hip and knee are imbalanced, this can cause the patella to pull slightly to one side, leading to maltracking. This misalignment concentrates the high compressive force onto a smaller area of the joint cartilage, which increases pain and stress. A tracking issue prevents the natural protective mechanism of load distribution from working effectively.
Three Primary Causes of Knee Pain
Patellofemoral Pain Syndrome (PFS)
Patellofemoral Pain Syndrome (PFS) is the most frequent diagnosis for pain felt behind or around the kneecap, especially during activities like squatting, running, or climbing stairs. Muscle imbalances in the hip and thigh are often implicated, as weakness in the hip abductors or quadriceps can contribute to poor patellar tracking.
PFS is commonly described as a dull, aching pain that worsens with deep knee bending or prolonged sitting with the knees flexed. This is sometimes called the “Theater Sign.” The issue is irritation of the underlying structures due to repetitive, uneven loading, not joint damage itself. Addressing the muscular control around the knee is a fundamental part of managing this condition.
Knee Bursitis
Knee bursitis is the inflammation of small, fluid-filled sacs called bursae, and it is a common cause of pain specifically aggravated by kneeling. The prepatellar bursa, located directly in front of the kneecap, is the most frequently irritated bursa. This bursa acts as a cushion between the skin and the bone, and prolonged, direct pressure causes it to become inflamed and swell.
The pain from bursitis is typically localized to the front of the kneecap and is often accompanied by noticeable swelling, tenderness, and warmth in the area. Another common location is infrapatellar bursitis, which affects the bursa located just below the kneecap. Unlike PFS, which is a deep, internal joint pain, bursitis pain is superficial and directly related to external pressure.
Patellar Tendinitis
Patellar tendinitis, often referred to as patellar tendinopathy, is an irritation of the patellar tendon, which connects the kneecap to the shinbone. This condition is frequently linked to repetitive jumping or explosive movements, earning it the nickname “Jumper’s Knee.” It is also aggravated by the high loads of deep squatting.
The pain is usually sharp and highly localized directly below the kneecap, at the point where the tendon attaches. Deep knee flexion places the maximum tensile load on the patellar tendon. The pain is load-dependent, meaning it increases directly with the intensity or depth of the squat. Modifying the depth of a squat to keep the load within a tolerable range is often necessary for managing this tendon issue.
Immediate Self-Care and Activity Modification
The first step in managing knee pain during squatting or kneeling is immediate activity modification to stay within a pain-free range of motion. Temporarily avoiding deep knee flexion allows the irritated tissues to settle down and prevents further aggravation. This modification may mean using a higher chair or bench for sitting, or using a stool instead of fully kneeling to perform tasks.
For acute pain or swelling, the RICE principle is an effective initial strategy. Resting means avoiding activities that provoke pain. Applying ice for 15 to 20 minutes every two hours during the first 48 to 72 hours can help reduce inflammation. Compression with an elastic bandage can help control swelling, and elevating the leg above heart level promotes fluid drainage.
Once acute pain subsides, incorporating simple, foundational exercises can help address underlying strength deficits. Quadriceps setting, which involves tightening the thigh muscle to press the back of the knee down, helps maintain muscle activation without joint movement. Straight leg raises, performed while lying on the back, strengthen the thigh muscles in a non-weight-bearing position.
Strengthening the muscles around the hip is also important for improving patellar tracking and stability. Exercises like the clamshell, performed lying on your side with the knees bent and lifting the top knee, target the stabilizing gluteal muscles. Gentle stretching of the quadriceps and hip flexors can also help reduce the tension that pulls the kneecap into the joint, thereby lessening the compressive load.
Warning Signs Requiring Medical Evaluation
While many cases of knee pain resolve with rest and self-care, certain symptoms indicate a potentially more serious issue that requires professional medical evaluation.
If you experience any of the following, seek prompt medical advice:
- An inability to bear weight on the affected leg.
- The knee feels unstable and prone to “giving way,” which can signal a ligament injury or a fracture.
- Significant, rapid swelling, especially when accompanied by redness, warmth, or a fever, which may point to an infection, such as septic bursitis.
- A visible deformity of the knee joint.
- A sensation of the knee mechanically locking or catching during movement.
If your pain does not begin to improve after a week to ten days of consistent self-care and activity modification, a physical therapist or physician should evaluate the joint for a definitive diagnosis.