Knee Injuries in Runners


Injuries to the knee are arguably the most common type of injury in runners. Though the differential diagnosis is quite broad (see Table 18.1 ), a more limited set account for the majority of complaints by runners. The purpose of this chapter is to review the assessment and differential diagnosis of knee pain in the runner, with a focus on evidenced-based evaluation and management of common conditions.

Table 18.1
Exhaustive Differential Diagnosis of Knee Pain With Common Locations of Symptoms.
Diagnosis Common in runners Anterior Posterior Medial Lateral Inferior Superior
Primary mechanical knee pain
Anterior cruciate ligament (ACL) sprain/tear x x x x
Biceps femoris tendinopathy x x
Bipartite patella (symptomatic) x
Fabellar fracture x
Fat pad impingement a x x x
Ganglion cyst x x x x x x
Gastrocnemius tendinopathy x x x
Iliotibial band syndrome a x x
Lateral collateral ligament (LCL) sprain/tear x
Loose body x x x x
Medial collateral ligament (MCL) sprain/tear a x
Meniscus injury a x x x x x
Osgood-Schlatter apophysitis a x x x
Osteoarthritis (lateral compartment) a x x x
Osteoarthritis (medial compartment) a x x x
Osteoarthritis (patellofemoral compartment) a x x x x
Osteochondral defect a x x x x
Osteochondritis dissecans x x x x
Osteonecrosis x x x x x x
Patellar subluxation a x
Patellar tendinopathy a x x x
Patellofemoral pain sydrome a x x x x
PCL sprain/tear x x x x
Pes anserine bursitis a x x x x
Pigmented villonodular synovitis x x x x x x
Plantaris tendinopathy/rupture x x
Plica syndrome x x x x x
Popliteal (Baker's) cyst a x x
Popliteus muscle strain or tendinopathy x
Prepatellar bursitis a x x
Proximal tibiofibular ligament sprain x x
Quadriceps tendinopathy a x x x
Semimembranosus tendinopathy x
Sinding-Larsen-Johansson apophysitis x x
Stress fracture a x x x x x x x
Referred knee pain
Arterial entrapment/aneurysm x
Common peroneal neuropathy x x
Genicular nerve entrapment x x x x
Intra-articular hip pathology a x x x x x x
Lumbar radiculopathy a x x x x x x
Myofascial pain a x x x x x x x
Myopathy x x x
Saphenous nerve entrapment x x x
Sciatic neuropathy x x x
Medical/other knee pain
Amyloidosis x x x x x x
Crystal-induced arthropathy a x x x x x x
Deep vein thrombosis x x
Hemochromatosis x x x x x x
Inflammatory arthropathy a x x x x x x
Lyme disease x x x x x x
Neurologic disorder (e.g., multiple sclerosis) x x x x x x
Sarcoidosis x x x x x x
Septic/infectious arthritis x x x x x x
Tumor/malignancy x x x x x x

a Common diagnoses.

A commonality among knee injuries in runners is the intimate relationship with the lower limb kinetic chain. Biomechanical abnormalities in the foot/ankle below and the hips/core above can often result in increased stress across the knee. It is of utmost importance for the clinician to identify any external factors contributing to knee pain when forming a comprehensive treatment plan.


The physical examination of the knee follows the standard musculoskeletal process of inspection, palpation, range of motion, and special testing. As with other peripheral joints, an asymptomatic contralateral knee is often present for comparison and should be tested. During inspection, note is made about the varus/valgus alignment of the knee, traumatic markers (abrasions, bruising, etc.), focal swelling, and presence of intra-articular effusion. With palpation, the examiner notes tenderness along the joint line, patella, patellar tendon, quadriceps tendon, external knee ligaments, tendinous insertions, and presence of an intra-articular effusion. Examining range of motion, one discerns if the runner can passively and actively extend and flex each knee painlessly and completely.

Special testing is tailored to the particular complaint. Many physical exam maneuvers exist for the knee, with highly variable sensitivities and specificities. In contrast to ligamentous maneuvers of the knee, which are rarely seen in atraumatic running injuries, most overuse-related knee exam maneuvers lack high sensitivities and specificities. The Clarke test is often used in the diagnosis of patellofemoral pain syndrome, with a positive test indicated by the presence of pain sufficient to prevent the patient from maintaining a quadriceps muscle contraction against manual resistance for longer than 2 s. It has a reported sensitivity of 0.39 and specificity of 0.67. Meniscal tests include the McMurray test and Apley grind test. Both have higher specificities (77%–90%) but low sensitivities (13%–37%). The McMurray test consists of starting with a supine patient and a fully flexed knee, then the leg is brought from its position of acute flexion to a right angle while the foot is retained first in full internal rotation and then in full external rotation. The Apley grind test contains similarities to McMurray's and is done with the patient prone. Another popular provocative technique for a meniscal tear, the Thessaly test, may be the most sensitive and specific, though other studies have demonstrated much lower values. For iliotibial band syndrome, the Ober test is commonly used, though its sensitivity and specificity have not been defined. It is performed by the examiner flexing the knee to 90 degrees in lateral lying position followed by abduction and extension of the hip to place the thigh in line with the trunk. Next, the examiner allows gravity to lower the thigh into adduction as far as possible while not allowing a change of thigh position in the sagittal or transverse planes.

Finally and possibly most importantly, a kinetic chain evaluation must be performed. Functional or structural abnormalities of the foot/ankle, hips, and core can significantly affect the knees. A single- and double-leg squat can give important information about the runner's neuromuscular control and strength. Since running is a sagittal plane motion, runners tend to be prone to coronal plane inefficiencies. The single-leg squat test can efficiently evaluate lateral structures' strength and control in the coronal plane. Running is a series of small-deviation single-leg squats; thus, a small control deficit can be magnified after several thousand steps. Pelvic drop and dynamic knee valgus are two commonly identified functional abnormalities seen in the runner that can lead to many types of knee pain. Ideally, observing running gait can be a useful part of the physical exam.


Though rehabilitation of runners' knee injuries is by no means a one-size-fits-all treatment, recurring themes are present. Lateral supporting structures are often weak or lack neuromuscular control, due to the sagittal plane nature of running. Lateral hip weakness can alter the loads placed on the knee, particularly the patella. Rehabilitation has shifted away from a sole focus on quadriceps strengthening to core and hip stabilizer neuromuscular reeducation and strengthening. Furthermore, tailoring the rehabilitation plan to the clinical problem while considering the runner's gait and deficiencies is ideal. A running analysis is essential for proper rehabilitation. Though a runner's gait may be atypical and not cause pathologic consequences, certain gait findings tend to predispose runners to more problems, such as contralateral pelvic drop, excessive anterior pelvic tilt, dynamic knee valgus, and excessive pronation. A structured, progressive approach to rehabilitation is usually followed, with the first phase focusing on minimizing irritation of the knee (often requiring a cessation or reduction in running mileage) and working on exercises to enhance proper neuromuscular control. The next phase involves increasing the load placed on the knee and further enhancing neuromuscular control. This is followed by training plyometric movements, and a gradual return to running.

Individual Diagnoses

Patellofemoral Pain

Patellofemoral pain (PFP) is one of the most common overuse injuries affecting runners with an estimated incidence of 3%–15% in active populations. In a study of 2002 runners presenting to a sports medicine clinic, the knee was the most common anatomic location of injury (42.1%) with 46% of these injuries being due to PFP. PFP affects female runners more than male runners, 19%–30% versus 13%–24%, respectively, and an age less than 34 years has been shown to be a risk factor in both sexes. It may also be a risk factor for the development of patellofemoral osteoarthritis (OA).

The patellofemoral joint is one of the most highly loaded joints in the body, and running places a tremendous cumulative load on the knee. A key intrinsic factor in the development of PFP is lateral patellar maltracking secondary to functional valgus of the lower limb, as seen in Fig. 18.1 . Contributors to functional valgus include inadequate hip strength (hip extensors, abductors, and external rotators), foot deformities (rear foot eversion, pes pronatus), vastus medialis/lateralis imbalance, as well as hamstring and iliotibial band tightness. Extrinsic factors are most often associated with training errors such as increased running mileage, speed, or rapid additions of hill, downhill, or stair running which can lead to the development of PFP.

Fig. 18.1, Functional/dynamic valgus of the lower limb. This includes internal rotation of the femur, valgus translation of the knee often with a lateral translation of the patella, and foot pronation. These can result from a variety of causes, such as hip abductor weakness, hip external rotation weakness, ankle instability, pes planus, and core weakness. 171

The core criterion defining PFP is retro- or peri-patellar pain aggravated by activities which load the patellofemoral joint, including running, jumping, squatting, and ascending or descending stairs. Additional criteria and symptoms can include mild to moderate joint swelling with associated crepitus, tenderness on patellar facet palpation and pain with prolonged sitting (“movie theater sign”), rising after sitting, or straightening the knee following sitting.

The clinical examination is considered by experts to be the cornerstone in diagnosing PFP; however, there are no definitive clinical tests or imaging findings in the diagnosis of PFP. The 2016 Patellofemoral Pain Consensus Statement from the 4th International Patellofemoral Pain Research Retreat determined the best available test is anterior knee pain elicited during a squatting maneuver. Tenderness on palpation of the patellar edges has limited evidence as well, but other tests including patellar grind testing, apprehension tests (i.e., Clarke's test), knee range of motion testing, and presence of effusion have low sensitivity and thus, low diagnostic accuracy for PFP.

Increasing literature has demonstrated that PFP can often become recalcitrant with certain factors, notably longer duration of symptoms (>2 months). This leads to a poor prognosis, emphasizing the importance of early intervention and treatment. Treatment for PFP in runners is exercised-based and should primarily focus on combined hip and knee exercises addressing muscular imbalances and promoting flexibility, which have been shown to improve pain and function in the short- and long-term better than isolated knee exercises. Initial therapy revolves around pain-free range of motion of the affected knee. Though closed-chain exercises provide lower patellofemoral joint stress, open-chain exercises may be an early option if the runner is particularly irritated. Training of the hip muscles (notably the hip abductors, extensors, and external rotators), in addition to the quadriceps, is the essential component of PFP therapy. Appropriate pelvic control is also enhanced with core stability exercises. It should be noted that simple strengthening of the aforementioned muscles is inadequate; incorporation of muscle activation (proper neuromuscular control) into running is key. After improved neuromuscular control, a gradual increase in load is placed on the runner, progressing to plyometric activities. A gradual return to running and increase in mileage is added throughout the rehabilitation process while pain-free. A running gait analysis may identify more functional kinetic chain abnormalities, including ankle motion, hip abductor strength, lumbopelvic posture, and upper body kinematics, which, in turn, allows a more individualized approach to the runner. Gait retraining may prevent the incidence of PFP.

Foot orthoses correcting foot deformities have been shown to improve PFP in the short term, but long-term benefits are inconclusive. Although there is evidence that shod running places increased stress on the patellofemoral joint compared with barefoot running, it is unclear how minimalist footwear translates into PFP symptom reduction and recovery. Taping may diminish symptoms during the recovery process, but likely does not address the underlying causative biomechanical deficits. It is important to address the biopsychosocial components of PFP given recent evidence of increased anxiety, depression, catastrophizing, and fear of movement in individuals with PFP, which can potentially hinder recovery and full return to running. Corticosteroid injections remain an option for treatment, but symptoms will likely recur without improvement of biomechanical factors. Surgical interventions for recalcitrant PFP may include lateral retinacular release and tibial tubercle osteotomy; however, an overwhelming minority of patients will require surgical intervention and early nonoperative management remains first line.

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